SNOW MONKEYS
The most northerly Old World monkeys
live in Honshu, Japan, where there is
deep snow in the winter. In some areas,
Japanese macaques have learned to
keep warm by sitting in hot springs,
where they often groom each other.
Modern apes long, curved
fingers
Chimpanzees, gorillas, and humans form a group of primates often called extremely
the “African apes,” which many authorities argue is descended from an long arms
ancestor that resembles Dryopithecus (see p.46); its Asian contemporary, attached to
Sivapithecus, gave rise to orangutans. Gibbons diverged earlier. highly flexible
shoulders
SIAMANG What is an ape? short face with
Found in the rain forests of Southeast Asia, large orbits ischial
the siamang is the largest of the gibbons, The teeth of apes are less specialized than those of callosities
weighing up to 30 lb (14 kg). Old World monkeys, but their skeletons are more JUVENILE GIBBON (like Old World
specialized. Apes have no tail; the caudal vertebrae, SKELETON monkeys,
which form the tail in most mammals, are reduced, The very long arms of but unlike
partly fused, and curved forward, forming the gibbons overshadow great apes)
coccyx, or tailbone (see p.52). Apes sit or stand the fact that they also
upright a good deal. Their lumbar vertebrae are have long legs; they
reduced in number and are short and stout to often walk bipedally
bear the weight of the upper body. They have along branches or on
broad chests, and their shoulder joints are highly the ground.
mobile, so they can extend their arms out to the
sides and above their heads. long, curved toes
Gibbons (all members of the hylobatid family)
have extremely long arms, which they use to swing
from branch to branch (a type of locomotion
called brachiation). They are medium-sized apes,
and their diet consists mostly of fruit.
The great apes Chimpanzees live in communities up to 120-strong, in which the
males are related, whereas females often leave and join another
Great apes are much larger than gibbons (which are often called group. Gorillas live in troops of 10–40, led by a silverback male.
lesser apes), more stockily built, and have shorter arms and legs Orangutans are solitary, although youngsters will remain with their
and short thumbs. Orangutans, which are highly arboreal, are mother until they are seven or eight years old. Male orangutans
restricted to rain forests and today are found only on the islands and gorillas weigh more than twice as much as the females.
of Borneo and Sumatra. The much more terrestrial gorillas live in
a variety of forest types, and chimpanzees, which are equally at pink facial skin of COMMON CHIMPANZEE
home in the trees and on the ground, can even live in wooded juvenile will darken The relaxed posture and facial
savanna. All, like gibbons, are mainly fruit eaters, but gorillas also with age expression of this young chimp
eat terrestrial herbaceous vegetation when available seasonally or reflect its mood. Like most
in habitats where they cannot get fruit, and chimpanzees often also primates, chimpanzees use
prey on monkeys, small antelopes, or other small mammals. their faces and bodies to
advertise their intentions.
grasping hands
and feet
BONOBO BORNEAN ORANGUTAN
A slighter built species of chimpanzee from the tropical forests of the The name orangutan is
Democratic Republic of Congo, bonobos exhibit different behaviors Malay for “man of the woods.”
from those of common chimpanzees, especially the use of sex between They typically have long
individuals of all ages as a way to reduce tensions in the community. reddish brown hair, whereas
the other great apes have
050 PRIMATES black or brownish black hair.
Most of their waking hours
are spent foraging for food.
WESTERN GORILLA
Like all apes, gorillas are completely
dependent on their mothers when born
and spend the first five months of their
lives in constant contact with them.
Infants are weaned at three or four years,
but the maternal bond remains strong.
Ape anatomy compared wrists and hands. When orangutans walk on all fours on the ground, they
place their weight on the outside edges of their palms, but much of their lives
Some of the most important differences between the skeletons of great apes are spent climbing in trees, and this also requires a highly modified skeleton.
and modern humans are related to their different ways of moving around. The big toe in humans is aligned with the other toes, whereas in gorillas (the
While all habitually sit upright, and often also stand upright, which requires a next most terrestrial ape), it is fairly divergent, and in chimpanzees, more so.
short and sturdy lower spine, humans are the only ones to always move by In orangutans, the big toe is very divergent and very short—their feet are
walking upright on two legs (bipedalism). Gorillas and chimpanzees move modified like hands, to serve their “four-handed” movement through the trees.
by knuckle-walking—a quadrupedal gait in which the fingers are flexed and
the weight is supported on the middle finger bones, requiring very strong
ORANGUTAN canines longer GORILLA large sagittal
in adult males
sagittal SKULL small braincase, SKULL crest in adult heavy brow
crest in Orangutans rectangular with flat, sloping ridge
mature primarily eat fruit. dental arcade males
The face is long forehead
males and concave and A gorilla’s skull has wide
the jaws are short broad
Iarge and deep. Like cheekbone teeth set in very heavy,
canine humans, their
skulls have no powerful jaws that jut
coccyx brow ridges. Fully
(tailbone) mature males have forward, and wide
a sagittal crest.
cheekbones to support the
large muscles needed to
long, chew tough leaves.
sloped face
foramen spine attaches
magnum large canine to rear of skull
shoulder joint
(hip bone) PELVIS rectangular large
ileum Wide hip bones support specially dental arcade projecting
developed muscles that are used jaws, but
sacrum to rotate the hip joints and give wide teeth
orangutans flexibility when climbing. no chin
foramen
shoulder joint spine attaches small, low magnum
allows arm to to rear of skull braincase
rotate farther
when climbing holding head cone-
horizontally shaped
rib cage
PELVIS
straight spine The stout pelvis has high, wide hip bones long arms
almost
short, sturdy lower hip bones that reach upward touch rib
(lumbar) region of spine cage
large projecting jaw, and nearly touch the rib cage,
hip bone but no chin short
providing stability for the heavy legs
coccyx (tailbone) cone-shaped rib cage
enables overhead upper body, and for the muscles
thigh bones roughly reaching while
parallel rather climbing that are needed to contain the
than angled
very long arms, enormous gut. coccyx
WHOLE SKELETON used for climbing hip bone
Orangutans have extremely more than walking
long arms and long, curved sacrum
fingers—both are adaptations
for climbing. Like the other coccyx thigh bones
great apes, they have flexible roughly parallel
feet. They usually have 12 rather than angled
ribs, like humans, whereas
gorillas and chimpanzees knee joint
usually have 13.
knee joint short thumb WHOLE SKELETON opposable
small calcaneus Like orangutans and thumb
(heel bone) short, chimpanzees, gorillas have a large
opposable cone-shaped rib cage, which calcaneus long, curved
052 PRIMATES big toe long, curved allows increased flexibility of fingers
the shoulder joint, enabling
fingers them to reach above their strong, opposable
heads when climbing. big toe
long toes
The head in humans is positioned directly above the spine so the foramen 18.4–33.3 cubic in (302–545 cubic cm); and gorillas, 24.6–41 cubic in
magnum (the large hole through which the spinal cord passes into the (403–672 cubic cm). Modern humans, which have the greatest brain to body
brain) is positioned much further forward on the skull than it is on the skulls size ratio of all, have a brain size of 61–122 cubic in (1,000–2,000 cubic cm),
of the great apes. One of the most important characteristics of primates is and this is reflected in the shape of the braincase. Gorilla and orangutan
their intelligence.All primates have large brains compared to their body size, skulls (and skeletons) show a high degree of difference between the sexes,
and this is seen to a greater extent in apes. Chimpanzees have a brain size chimpanzees and humans less so. Some of the other differences in the skulls
(cranial capacity) of 18.6–29.6 cubic in (305–485 cubic cm); orangutans, are related to differences in diet.
CHIMPANZEE MODERN HUMAN projecting
nasal region
flat, brow ridge large canine high, large
nonprojecting rectangular braincase short, flat
SKULL dental arcade SKULL face
nasal region Chimpanzees have small A human skull is higher pointed
smaller molars than foramen front and more rounded than chin
gorillas, but their magnum teeth those of the great apes.
incisors are larger and The face is flat, and the skull
broad to cope with large small jaws and teeth are much positioned
their omnivorous projecting canine smaller, perhaps because directly
diet. The upper part jaw, but cooked food requires over spine
of the face is flatter, no chin less chewing.
and their brow barrel-shaped
large front ridges are smaller cone-shaped narrow shoulder rib cage
teeth than in gorillas. rib cage cheekbones joint allows arms
to swing while
PELVIS small, low braincase curved dental walking
The very long, narrow pelvis keeps the arcade caused
legs at the correct angle to the torso spine attaches to rear by short face short, wide
when knuckle-walking and climbing. of skull holding head pelvis positions
It broadens only at the top, where the lumbar region body directly
gluteus medius—a muscle aiding at an angle curves forward above hips
side-to-side stability—is attached.
shoulder joint under center thigh bones
of gravity angled inward
hip bone toward knees
foramen
long magnum shorter, slender,
sacrum straight fingers
sacrum
knee can lock,
rounded enabling leg to
braincase extend fully in a
long walking
coccyx PELVIS coccyx stride
The human pelvis is shorter and wider hip bone
than those of the great apes. This legs longer
centers the torso above the hips, and than arms
the deep hip sockets stabilize the hip
joints so they can support the full body arched foot
weight when walking upright. big toe fully aligned
with other toes
long, arms longer
narrow than legs
pelvis
opposable
coccyx thumb sacrum with five
long, curved (sometimes six as here)
WHOLE SKELETON fingers fused segments
opposable
Chimpanzees occasionally walk big toe large knee joint, so
long toes leg can support
upright, but their skeletons are
body’s weight while
not adapted for walking (or walking long
distances
running) long distances on two thigh bones
legs as humans can. Like the roughly
other great apes, their thigh parallel rather coccyx
bones are roughly parallel than angled
rather than angled, which gives
them a rocking gait when they lightly built knee WHOLE SKELETON
do walk upright. The size of the joint, so leg can only A human spine is S-shaped: it curves
calcaneus (heel bone) is related forward in the neck, backward in the
to the amount of time spent on support weight for chest, forward in the lumbar region,
short periods of and backward in the sacrum. These
curves keep the body balanced upright
the ground, so a chimpanzee’s bipedal walking and allow the spine to absorb the
shock of impact when walking or
is smaller than a human’s. The running. The thigh bones slant inward
from the hips to the knees, placing the
pelvis does not reach up to the knees under the center of gravity.
rib cage, and this gives the body medium-sized very large
greater flexibility. A chimpanzee’s calcaneus calcaneus
arms are only a little longer than
its legs; in bonobos, they are
the same length.
MODERN APES 053
1
Apes and humans
Great apes and humans are grouped as a single family, the hominids, and scientists Human or ape?
even consider humans to be a species of ape. Humans belong in the hominin tribe,
of which only one species remains today. Genetically, humans are closest to It is very difficult to draw the line
chimpanzees and, reciprocally, chimpanzees are closer to humans than to gorillas. between human and ape in the fossil
record. DNA evidence suggests that
long, curved orbital region vertical orbital the common ancestor we share with
canine slopes back region chimpanzees lived about 7.4 million
years ago, but the search for fossils
deep, vertical COMPARING SKULLS documenting this period has become
premaxilla From about 13 million more of a problem than it used to be.
years ago, apes like Scientists have always assumed that
deep, vertical Pierolapithecus already the human lineage begins where
premaxilla showed similarities in features associated with walking on
short, stout the lower face to early two feet (bipedalism; see p.53, 69),
canine hominins such as short jaws, and short, stout canines
Australopithecus, are first seen in a species in the fossil
PIEROLAPITHECUS while retaining a record, but this is not clear-cut.
primitive sloping form The recent suggestion that the
of the orbital region common ancestor with chimps and
unchanged from gorillas was already somewhat
Proconsul and even specialized for bipedalism has been
Aegyptopithecus controversial: most authorities regard
(see p.43). this as unlikely.
AUSTRALOPITHECUS
AFARENSIS
054 PRIMATES
1. Leaf rain hat. Orangutans are especially 2 Anything you
known for their mechanical flair, such as can do...
prying open fruit with a stick. They frequently
use large leaves to protect themselves All great apes exhibit skills and
against the rain. intelligence well beyond the
2. Termite fishing stick. Chimpanzees capabilities of monkeys or even
have long been known to use grass stems or gibbons. They make complex nests
sticks to extract termites from their mounds. for sleeping in at night. They practice
Termiting skills take different forms in strategic planning in their social lives.
different chimpanzee populations. Wild chimpanzees and orangutans
3. Leaf sponge. To extract water to drink make simple tools and bring them to
from holes in trees, chimpanzees often make the sites where they will use them
“sponges” from leaves. Orangutans have —further evidence of foresight and
been observed doing this in the wild as well. planning. They also use different
4. Nutcracker. tools in sequence; chimpanzees will
Although gorillas use tools much less than place a nut on a stone, and use
chimpanzees or orangutans there are still another stone to crack it. One gorilla
impressive examples of tool use, such as wading across a pool was seen
using stones both as hammer and anvil using a stick to test its depth.
to crack nuts.
When tested in laboratories, great
43 apes can solve complex psychological
problems. They can also recognize
themselves in mirrors—like humans,
they are self-aware.
it is possible that knuckle-walking Close relatives LANGUAGE SKILLS
evolved independently in chimps and Great apes have
gorillas. Several evolutionary lines of By how much of their DNA do humans and chimpanzees differ? The been taught simple
apes did independently evolve short percentage is different according to how it is calculated. In non-coding communication with
canines in the Late Miocene. The DNA (so-called “junk DNA”) it is about 1.2%, but in coding DNA (actual humans (and with
7–9-million-year-old Oreopithecus genes) it is, unexpectedly, less, only 0.6%, whereas over their genomes as each other). Early
from Italy appears to have shown a whole, because quite large sequences have been deleted and inserted, programs used
bipedal specializations and had a it is much more, about 5%. Most calculations take the difference in non- sign language, and
very short face and small canines, but coding DNA as the “true” difference. At any rate, humans and chimpanzees impressive results
it was almost certainly not a direct are very closely related indeed, and separated only about 7.4 million years have been achieved
ancestor of our genus, Homo. ago, whereas the ancestors of gorillas separated a little over 10 million with bonobos using
years ago, and those of orangutans about 15 million years ago. special symbols.
Ardipithecus ramidus, which lived
4.4 million years ago, was partially 3.1% DIFFERENCE CHIMPANZEE JANE GOODALL
bipedal, although still a tree-living ape,
and had rather small canines and ORANGUTAN 1.6% DIFFERENCE 1.6% DIFFERENCE British primatologist Jane Goodall
short jaws. It was only later, during the 1.2% DIFFERENCE (1934– ) began her study of
evolution of Australopithecus (from 3.1% DIFFERENCE chimpanzees in Gombe National
4.2 million years ago) and then early Park, Tanzania, in 1960. She was
Homo species (from 2.4 million years DNA DIFFERENCES DIFFERENCE HUMAN the first to observe toolmaking
ago), that the full development The percentage differences in 3.1% GORILLA by wild chimpanzees. She
of completely human bipedalism, non-coding DNA are as follows: documented chimpanzee society,
distinctive shapes of teeth, and, humans from chimpanzees, their behavioral flexibility, their
finally, brain enlargement is seen. 1.2%; gorillas from humans emotional life, their cooperative
and from chimpanzees, 1.6%; hunting, and their wars against
orangutans from humans, neighboring communities.
from chimpanzees, and from
gorillas, 3.1%.
APES AND HUMANS 055
HOMININS
The term “hominin” is used to describe living humans
and all other species comprising the lineage that diverged
from that of chimpanzees around 7 million years ago.
The 23 hominins profiled here represent the extent of
the current fossil record. Only some of them are our
ancestors, and many became extinct without giving
rise to new species. Although the relationships between
these hominins are complex and often unresolved,
various aspects of their fossil remains have enabled us
to place them in groups or genera, including Homo, to
which our own species, Homo sapiens, belongs.
Human evolution
The fossil record for human evolution stretches back at least 7 million years. Early sites
are now known from eastern, central, and southern parts of Africa, and later sites have
been found across many parts of Europe and Asia. After nearly 150 years of scientific
investigation, there is strong evidence for the general pattern of human evolution.
SAHELANTHROPUS AUSTRALOPITHECUS AUSTRALOPITHECUS
TCHADENSIS AFARENSIS AFRICANUS
Becoming human 50 MILLION YEARS AGO 25 MILLION YEARS AGO PRESENT DAY
Members of the same species have The groups mix less and less; there is less Ultimately, sufficient mutations build up in both
Humans have much in common, anatomically and the same genetic makeup. But over
behaviorally, with other primates. This close biological time, two different groups within the opportunity or willingness to interbreed, groups’ genomes that they are no longer able
kinship is also indicated by DNA evidence (see p.36), which and mutations (the circled genes) begin to to interbreed, so they become distinct species.
shows that our closest living relatives are bonobos and species face different selective
chimpanzees. There is only about 0.1 percent difference pressures, and/or meet the same distinguish the two groups. CAATCGATCG
between the chimpanzee genome and our own (see p.55), selective pressures in different ways.
suggesting that we share a common ancestor. Genetic CAATTGATCG
mutations occur at similar rates across different lineages, CAATTTATCG
and accumulated change can be used to estimate the CAATTTATCT
date of species divergence. According to this “molecular MOLECULAR CLOCKS
clock,” the last ancestor we shared with chimpanzees In this hypothetical example, four CAATTTATTT
probably lived between 8 and 6 MYA. One of the challenges genes differentiate two species.
in paleoanthropology is working out what this common From the known mutation rate
ancestor looked like, how it behaved, and what selection of those genes we can calculate
pressures resulted in the appearance of the first hominin. back for a common ancestor.
058 HOMININS
“Human” species (shape) of bones is used to group fossils into populations, AFRICAN ANCESTORS
and if these populations are distinctive enough, a new This lineup shows some of the African
Many biologists observing living animals define a species species is proposed. It is even possible that the definition members of the human evolutionary tree,
as a group of interbreeding natural populations that are of a species may rely on a single very unusual fossil spanning back 7 million years. While it
reproductively isolated from other such groups. This is specimen. As new finds are made and the understanding appears linear here, the map of human
the “biological species” concept. Paleoanthropologists of the fossil record grows, the names of hominin species evolution looks more like a tree, with several
cannot observe the behavior of extinct hominin species, may be redefined, grouped, or eliminated. branches, for example Homo habilis and
so they have to rely on the fossils themselves for clues Homo ergaster, living at the same time.
about their distinctiveness. Variation in the morphology
HOMO HABILIS HOMO ERGASTER HOMO HOMO SAPIENS
HEIDELBERGENSIS
DNA KARYOTYPE Genetics EVE
The human genome contains 46 chromosomes, while our close CURRENT GENERATION
relatives the great apes have 48. In the human lineage, two The science of genetics reveals mechanisms at the heart
chromosomes inherited from the ancestors we shared with the of evolutionary processes. Traits are encoded in genes—
other apes have fused together to form the human chromosome 2. hereditary units of DNA in the chromosomes of our cells.
Natural selection, geographic isolation, mutation, and
other processes can change the genetic profile of
populations over time and produce new species. Genetic
studies have shown that all living humans are closely
related, sharing a common ancestor who lived about
200,000 years ago, and research into Neanderthal DNA
has revealed possible interbreeding with modern humans.
MITOCHONDRIAL EVE
We inherit mitochondrial DNA (mtDNA) only from our mothers. By
comparing differences between mtDNA lineages, and estimating the
rate at which they appeared, it is possible to trace the lineages back
to a common female ancestor, known as “Mitochondrial Eve.”
HUMAN EVOLUTION 059
Family tree
Genetic and fossil evidence suggests that the first hominins appeared KEY TO GENUS
in Africa between 8 and 6MYA, with many species appearing after this time.
Their genetic relationships probably form a complex web, and until SAHELANTHROPUS
relatively recently several hominin species existed at any one time. ORRORIN
ARDIPITHECUS
Trends through time KENYANTHROPUS
PARANTHROPUS
Several specimens, such as Sahelanthropus tchadensis and Orrorin tugenensis, AUSTRALOPITHECUS
suggest that the earliest hominin species were modest in size, had brains no HOMO
larger than those of modern apes, and exhibited a unique suite of physical
characteristics that allowed both upright walking and climbing. Over time, and
in the context of changing selection pressures, populations appeared with new
characteristics, and a number of evolutionary trends can be identified. Powerful
jaws and large back teeth, ideal for chewing tough or fibrous foods, appear in
some species. Large brains relative to body size and smaller jaws and teeth
appear in others. Bipedalism became the dominant mode of locomotion, and
all the later hominins were characterized by their use of stone-tool technology.
ORRORIN TUGENENSIS ARDIPITHECUS RAMIDUS KENYANTHROPUS PLATYOPS AUSTRALOPITHECUS BAHRELGHAZALI AUSTRALOPITHECUS GARHI PARANTHROPUS AETHIOPICUS
6.2–5.6 MYA
4.5–4.3 MYA 3.5–3.3 MYA 3.6–3 MYA 2.5–2.3 MYA 2.7–2.3 MYA
7 MYA 6 MYA 5 MYA 4 MYA 3 MYA
AUSTRALOPITHECUS ANAMENSIS AUSTRALOPITHECUS AFARENSIS HOMO HABILIS
4.2–3.9 MYA 3.7–3 MYA 2.4–1.6 MYA
SAHELANTHROPUS TCHADENSIS ARDIPITHECUS KADABBA
7–6 MYA 5.8–5.2 MYA
AUSTRALOPITHECUS AFRICANUS
3.3–2.1 MYA
060 HOMININS
PARANTHROPUS BOISEI HOMO ERGASTER HOMO ERECTUS HOMO HEIDELBERGENSIS HOMO NEANDERTHALENSIS
2.3–1.4 MYA 1.9–1.5 MYA 1.8 MYA–30,000 YEARS AGO 600,000–200,000 YEARS AGO 350,000–28,000 YEARS AGO
2 MYA 1 MYA
HOMO ANTECESSOR HOMO FLORESIENSIS
1.2 MYA–500,000 YEARS AGO 95,000–12,000 YEARS AGO
PARANTHROPUS ROBUSTUS
2–1.2 MYA
AUSTRALOPITHECUS SEDIBA HOMO GEORGICUS HOMO SAPIENS
1.95–1.78 MYA 1.8 MYA 200,000 YEARS AGO–PRESENT DAY
FAMILY TREE 061
Sahelanthropus
tchadensis
Sahelanthropus lived around the time of the last common
ancestor of humans and other apes, but its position on
the human family tree is far from certain.
SAHELANTHROPUS TCHADENSIS Sahelanthoropus tchadensis, described
NAME MEANING “The Sahel man
from Chad” in 2002, was found in Chad—far away from the East
AGE 7–6 mya African Rift Valley and South Africa, where the search
HEIGHT Unknown for early hominins had previously been concentrated.
BRAIN SIZE 19–23cuin (320–380cc)
LOCALITY Discovery FOSSIL SKULL IN SITU
Toros-Menalla, The single S. tchadensis skull discovered,
Chad In 2001 the Mission Paléoanthropologique Franco-Tchadienne, a joint venture known as Toumai (“Hope of Life”) in the local
between universities and research institutes in France and Chad, began to language of Chad, was found exposed on
FOSSIL RECORD Single skull, recover fossils from the Toros-Menalla area of Chad’s Djurab Desert. There the surface in loose sand. This made exact
fragments of jaw and teeth are no absolute dates for these finds, but comparisons with animal fossils dating difficult, since it may have been
from other sites suggest that the material is 7–6 million years old. The fossils, moved or even reburied in the recent past.
which represent nine individuals, include a relatively complete skull, four
jawbone fragments, and a few teeth. No fossils of other body parts are
known, making direct comparison with early hominin skeletons difficult. Some
of the cranial characteristics are similar to those of Miocene apes, and others
more similar to later hominins. However, the fossil finds are separated from
these groups by both time and geography, so the new genus seems justified.
Physical features VIRTUAL SKULL RECONSTRUCTION MODERN HUMAN CHIMPANZEE
AUSTRALOPITHECUS AFRICANUS SAHELANTHROPUS
Sahelanthropus has several features in common with A computed tomography (CT) scan
later hominins such as Kenyanthropus and Homo. The was used to make a digital version
canines are relatively small and show wear at their tips, of the Sahelanthropus skull. The
and the tooth enamel is thicker than is seen in apes. elongated skull has a horizontal
The face is also quite flat compared with apes, and the base and a short, vertical face, as
brow ridge is massive and continuous above the orbits. in later hominins. The opening for
In many other respects, however, Sahelanthropus does the spinal cord is oval, downward
resemble living and extinct apes. The cranial capacity pointing, and positioned toward the
is small, and the shape of the rear part of the skull is front of the skull, suggesting that
a truncated triangle. It has been argued that because the head was balanced on an erect
Sahelanthropus presents this mosaic of primitive and spine. These features are shared
recently evolved characteristics, it probably should be with later bipedal hominins, such as
placed on the human family tree close to the last Australopithecus africanus and
common ancestor of humans and chimpanzees. Homo sapiens, but not other apes.
brain size similar DISTORTED FOSSIL
to that of a Although the fossil skull TM 266-0-60-1 was
chimpanzee remarkably well preserved, it was badly cracked
and distorted, with the entire right side of the skull
depressed and most of the teeth broken. In this
model, created from images of the original fossil,
the distortion has been reduced.
thick brow
ridges
face quite flat compared smaller canines than long skull with
to modern apes in earlier species protruding rear
SKULL Despite the condition of the
fossil skull, it is clear that the face is
short, less projecting than in modern
apes, and set high in front of the cranial
vault. The eye sockets are widely set
and topped by a strong brow ridge. The
brain size, reconstructed by computed
tomography (CT), was about 22 cubic in
(365 cc), toward the lower end of the
range that is seen in modern apes.
064 HOMININS
CHANGING CLIMATE
EFFECTS ON HUMAN EVOLUTION
Paleoanthropologists are trying to unravel the role of WOODLAND
climate change in human evolution. In sub-Saharan Africa, African apes still live in forest and
geological evidence from the last 10 million years suggests woodland habitats, suggesting that
a trend toward cooling temperatures, while the uplift of they were important in early hominin
the East African Rift System led to increased dryness. evolution. Bipedal, ground-living
These factors probably caused a shift from woodland to primates like the early hominins
grassland. Superimposed on such long-term trends was probably lived in open, seasonal
extreme climate variability, with with East African lakes woodlands rather than in dense
fluctuating between high and low water levels. tropical forests. Here food resources
are less predictable, and exploiting
The Savanna Hypothesis them successfully requires flexibility
in diet and in foraging behavior.
There are several hypotheses linking African climate change
to hominin evolution. The long-held savanna hypothesis GRASSLAND
states that increasing aridity and the spread of savanna The African savanna and other
habitats drove the evolution of hominin characteristics such grassland habitats are more open
as bipedalism and increased brain size. Evidence for these than woodlands. They tend to
trends comes from carbon-isotope data in soils (see p.10), support a larger number and greater
faunal remains, ocean sediments, and an apparent correlation diversity of terrestrial mammal and
in timings of climate change and the appearance of new plant species. Many food resources,
hominin species. Upright walking, it is suggested, was the such as nuts, underground tubers,
most efficient way of moving over open grasslands, with and bone marrow scavenged from
the added benefit that it freed the hands for carrying items animal carcasses, could only be
or for making tools. However, recent evidence is challenging accessed by hominins using tools.
this view, suggesting that the relationship between climate
change and hominin evolution is far more complex. HOMININ GENERA
Pulsed Climate Variability Hypothesis habitat-specific traits to be replaced by adaptations that are HOMO
responsive to rapidly changing environments. These ideas
If key hominin characteristics evolved in response to the have been refined still further by Mark Maslin and Martin AUSTRALOPITHECUS
selection pressures of a savanna habitat, it is unlikely that Trauth in the “Pulsed Climate Variability Hypothesis,” which
hominin fossils with these characteristics would be found in suggests that the transitional phases between wet and dry PARANTHROPUS
any other habitat type. However, Ardipithecus remains have periods suffer very extreme climate variability over short
now been found in woodland habitats, and Australopithecus timescales, and that it is these pressures that could have KENYANTHROPUS
anamensis fossils found in association with mixed had a marked effect on the appearance of new species.
grassland and gallery forest environments. This suggests ARDIPITHECUS
that perhaps the hominin skeleton was very adaptable and HOMININS AND EXTREME CLIMATE PERIODS
allowed individuals to flourish in a range of habitats, whether The emergence of many new hominin species seems
wet or dry, open or wooded. Recent research has shown to have coincided with periods of highly variable
that Africa experienced extreme climate variability, which in climate. It may be that the physical and behavioural
turn would have caused significant variability in vegetation flexibility of hominin species evolved so that they could
and water availability. The “Variability Selection Hypothesis,” cope in a range of environmental conditions.
developed by Rick Potts, suggests that large climate
fluctuations (as opposed to gradual climate change) cause
vertical bands show HOMO SAPIENS
transitional phases HOMO NEANDERTHALENSIS
of extreme climate HOMO HEIDELBERGENSIS
variability, between HOMO ANTECESSOR
wet and dry periods
HOMO ERECTUS
KENYANTHROPUS PLATYOPS HOMO ERGASTER
AUSTRALOPITHECUS AFRICANUS HOMO GEORGICUS HOMO FLORESIENSIS
AUSTRALOPITHECUS BAHRELGHAZALI HOMO HABILIS
AUSTRALOPITHECUS AFARENSIS AUSTRALOPITHECUS GARHI
AUSTRALOPITHECUS SEDIBA
ARDIPITHECUS RAMIDUS PARANTHROPUS ROBUSTUS horizontal bands represent the
appearance and duration of
AUSTRALOPITHECUS ANAMENSIS PARANTHROPUS AETHIOPICUS different hominin species
PARANTHROPUS BOISEI
5 MYA 4 MYA 3 MYA 2 MYA 1 MYA
SAHELANTHROPUS TCHADENSIS/CHANGING CLIMATE 065
INCHES00 SIDE RIGHT
skull about the
same size as that
of a chimpanzee
01
relatively flat
lower face
02 tucked under
braincase
Reconstruction relatively small
jaw does not
This representation of Sahelanthropus tchadensis is based on measurements protrude as far as
taken from the only skull yet found of this hominin species. Nicknamed “Toumaï” in other primates
(“hope of life” in the local Dazaga language of Chad), the skull has a mixture
of primitive, apelike features and others characteristic of later hominins. It
was partly crushed and distorted, and some of its details had been eroded
by wind-blown sand because it had lain exposed in the open. This presented
a challenge to the modelers attempting to reconstruct Toumaï’s possible
appearance, necessitating a considerable amount of educated guesswork.
066 HOMININS
FRONT RIGHT FRONT dark facial skin
eyes, like those of other protects against
FRONT LEFT primates, probably did UV radiation from
heavy ridge of not have visible whites the sun, and gets
bone over eyes darker with age
typical ape and exposure
nose is wide
and flat, unlike
human noses
SIDE LEFT
face surprisingly head probably positioned
modern for such more squarely over an
an early species erect spine, compared
with knuckle-walking
apes, such as gorillas
and chimpanzees
SAHELANTHROPUS TCHADENSIS 067
Orrorin tugenensis
A contender for the title of the earliest bipedal hominin, Physical features
Orrorin tugenensis may have inhabited ancient lakeside
woodlands and wet grasslands. The shaft of a human femur (thigh bone) is
a very strong cylinder, adapted to the heavy
ORRORIN TUGENENSIS Discovery loading of bipedal walking. In Orrorin tugenensis,
the femur has particularly thick bone in the upper
NAME MEANING “Original man of In 1974, a fossil molar tooth was part of the shaft—evidence for bipedalism.
the Tugen Hills” unearthed by palaeontologist Martin The shape of the upper arm bone and the slightly
AGE 6.2–5.6 mya Pickford from late Miocene deposits curved finger, however, indicates that the upper
HEIGHT Unknown at Cheboit, Kenya. With low cusps on limbs were weight bearing too. The pointed
BRAIN SIZE Unknown the chewing surface and thick enamel, canine tooth, low cusped molars, and large
LOCALITY Cheboit it did not fit into any known species. upper front tooth may reflect a diet of fruit and
in the Lukeino Pickford named it Orrorin tugenensis seeds. Taken together, this could imply a
Formation at the following year, but it was nearly mixed arboreal and terrestrial lifestyle.
Tugen Hills, Kenya 30 years until the next major find. A
French–Kenyan team led by Pickford parts of three separate femurs were
FOSSIL RECORD Jawbone, teeth, and French palaeontologist Brigitte discovered, although only one was
fragmented arm, thigh, and Senut returned to the region and in
finger bones 2001 announced the discovery of well-preserved enough to prove Orrorin
teeth and fragments of the arms walked on two legs
and legs of several individuals. This
species may have been one of the ORRORIN THIGH BONE
earliest members of the human Several features of Orrorin’s femur suggest
lineage to walk upright. that it walked on two legs. The round shape
of the ball joint that fits into the hip socket,
its orientation to the shaft, and the position
of marks from hip muscles on the bone are
like those of bipeds.
Ardipithecus kadabba
Notable for its large, projecting canine teeth, Ardipithecus kadabba Physical
may be related to later hominin species such as Australopithecus features
anamensis (see p.75) and Australopithecus afarensis (see pp.78–79).
The teeth of Ardipithecus kadabba
ARDIPITHECUS KADABBA Discovery share some characteristics with
NAME MEANING From the Afar those of great apes. The canines are
word for “basal family ancestor” In 2004, anthropologists Tim White (USA), Gen Suwa (Japan), and Berhane large and project past the chewing
AGE 5.8–5.2 mya Asfaw (Ethiopia) renamed a small collection of fossil fragments from the Middle plane of the molars. They are also
HEIGHT Unknown Awash River Valley, Ethiopia, as Ardipithecus kadabba. Excavated over the worn along the length of the tooth—in
BRAIN SIZE Unknown previous decade, the fossils were first thought to be an australopithecine modern apes, this is caused by the
LOCALITY Middle species, and then a subspecies of Ardipithecus ramidus. Now the material is teeth interlocking. However, the
Awash, Ethiopia seen as a species in its own right, largely on the basis of dental anatomy and molar enamel is thicker than that of
geological date. The fossils were found with remains of extinct animals such chimpanzees, but thinner than in later
FOSSIL RECORD Fragments of hominins. It is likely that this species
jaw, arm, hand, foot bone, and as the four-tusked elephant enjoyed a diet of fruit and soft leaves.
collarbone Deinotheirium and the three-
toed horse Hipparion, as well Some fragmented limb bones have
as wetland and woodland been ascribed to A. kadabba, but they
species still alive today. remain controversial. The orientation
and shape of the toe may suggest a
AWASH LANDSCAPE grasping foot, and the dimensions of
Ardipithecus kadabba’s habitat was the arm may indicate a body size like
a mix of woodland and grassland, australopithecines, but until a more
with springs, swamps, and small complete A. kadabba skeleton is
lakes—not quite as arid as the found, few conclusions can be drawn.
Awash landscape appears today.
068 HOMININS
BIPEDALISM
ANATOMICAL FEATURES
Upright walking on two legs, or bipedalism, is one of the FORAMEN MAGNUM
most distinctive human features. Other primates may stand The spinal cord passes through a large opening in
on their hind limbs to reach food, or briefly walk bipedally to the skull called the foramen magnum. This is at the
cross open spaces, but they swiftly return to quadrupedalism rear of the skull in quadrupeds, but in bipeds
or climbing. Bipedalism gave our ancestors many advantages: the skull sits on a vertical spine, so the foramen
it was an efficient way of traveling long distances; it helped magnum is tucked under the base of the skull.
maintain a moderate body temperature by minimizing
exposure to the sun; it raised the line-of-sight for spotting SPINE
predators; and it freed the hands for using tools. The To accommodate our upright stance, the human
adaptations that allow us to walk bipedally can be found spine is more curved in the neck and lower back
all over our skeletons. than that of a gorilla. This S-shape brings the
body’s center of gravity close to the midline above
GORILLA HUMAN the feet and allows the spine to flex during walking.
RIB CAGE KNUCKLE-WALKING GORILLA
The human rib cage is barrel shaped so that the Our closest modern relatives, the chimpanzees
torso can flex and the arms swing freely, which and gorillas, are “knuckle-walkers,” resting on
aids balance while walking bipedally. Gorillas their knuckles, rather than their palms or fingers,
have a cone-shaped rib cage to accommodate while moving on the ground.
a large gut below and permit a wide range of
motion at the shoulder, enabling them to THIGH BONE
reach above their head when climbing. The human femur (thigh bone) transfers the body’s
weight from the pelvis to the feet through the
PELVIS knees, so it has large joint surfaces and a shaft
The human pelvis is shorter and wider than that angled toward the body’s midline and center of
of other primates, with the base of the spine gravity. In contrast, most other primates have
close to the large hip-joint socket. This shape shorter, less angled femurs with smaller joints.
supports the upper body, enables the pelvis to
tilt, and maintains balance in upright walking. BIPEDALISM 069
FEET
The feet of most primates are adapted to grasping
and quadrupedal movement, with divergent big
toes and flat soles. In humans, large big toes
aligned with the other toes, well-developed arches,
and wide heels allow the foot to push off with the
toes and absorb the forces of walking.
Ardipithecus ramidus
Ardipithecus ramidus is known from the remains of many Physical features
individuals, representing almost the entire skeleton, and
it provides an insight into the appearance of bipedalism The partial remains of many individuals have been discovered and described
and habitat selection in early hominin evolution. —unusual for such an ancient species—and fossils of almost every part of
the skeleton have been found. Analysis of these specimens has shown that
Discovery Ardipithecus ramidus was of modest stature and probably presented very
little sexual dimorphism (size difference between the sexes). Many features of
In 1992, a single hominin molar tooth was discovered by the Japanese the arms, hands, and feet suggest that they employed a mixed pattern of
anthropologist Gen Suwa in the Aramis locality 1 site of the Middle Awash River movement, partially bipedal and partially arboreal. The dentition suggests a
Valley in Ethiopia. This locality was known to contain a rich paleontological broad diet, and the brain is small compared to that of later hominins.
record, including fragmented remains of woodland plants and animals, but
this was the first hominin evidence found there. The specimen remained HEIGHT Female: 3ft 11 in (1.20 m)
unclassified until 1993, when a research team led by American anthropologist
Tim White found the remains of at least 17 individuals, mostly represented by WEIGHT Female: 110 lb (50 kg)
teeth. Together, these were used to describe a new species: Australopithecus
BRAIN SIZE 18–23 cubic in (300–370 cubic cm)
ramidus. In 1995, the species genus
was changed to Ardipithecus. Today, “ARDI” – THE OLDEST HOMININ SKELETON
the species is represented by more In November 1994, Ethiopian paleoanthropologist Yohannes Haile-Selassie
than 100 specimens, including the collected two hominin hand bones from the surface of an exposed clay
remarkably complete skeleton deposit at Aramis. Soon finger bones, then a thigh bone and a lower leg
ARA-VP-6/500. Many of these fossils were revealed, and by the end of 1995 more than 100 more fragments from
come from contexts that can be the same skeleton had been found. The remains were poorly fossilized and
confidently dated, and the species is fragile, and it took the research team several years of meticulous laboratory
thought to have lived between about work to stabilize them. The partial skeleton ARA-VP-6/500, known as
4.5 and 4.3 million years ago. “Ardi,” includes a fragmented but quite complete skull, remains of both
arms and hands, parts of the pelvis, leg, and both feet. It is identified as
GIDAY WOLDEGABRIEL female because it has smaller canines, a smaller cranial capacity, and
The Ethiopian-born geologist Giday a more lightly built face than other specimens.
WoldeGabriel has been involved in the
discovery of many significant fossil
specimens, especially during his involvement
with the Middle Awash Project in East Africa.
ARDIPITHECUS RAMIDUS ARDI’S ENVIRONMENT
NAME MEANING “Root of the ground apes” The hominin-bearing deposits of the
Middle Awash are rich in evidence
LOCALITY Aramis in Middle of Ardipithecus ramidus’s local
Awash, and Goma (near Hadar), environment. Fossilized wood
Ethiopia fragments, seeds, and the remains
of mammals such as antelopes and
8 MYA PRESENT AGE 4.5–4.3 mya monkeys all indicate an ancient
7 MYA 1 MYA woodland or forest habitat at a time
6 MYA Dated through absolute when drought was rare. Biomolecular
2 MYA dating of volcanic ash studies of the teeth of several
layers above and below A. ramidus individuals have suggested
the fossils that their diet was dominated by the
products of shrubs and trees, which
5 MYA 3 MYA also points to a preference for
woodland habitats rather than the
4 MYA open savanna and grassland so
often associated with later hominins.
FOSSIL RECORD One nearly complete skeleton; various
skull, jaw, teeth, and arm fragments FOREST DWELLERS
Many of the animal species whose remains
are associated with those of A. ramidus,
such as colobus monkeys (above) and kudu
(below), eat leaves and are still usually
found in forested environments today.
070 HOMININS
relatively small
small skull brow
smaller premolars neck bone canines project less projecting
and molars than later first rib than those of apes face
australopithecines
SKULL Similar in appearance to Sahelanthropus ARDI SKULL
long arm bones vertebra (see p.64), the Ardipithecus skull has a small cranial The bones and especially the skull
indicate that A. capacity, a strong but short mid-face, and relatively were found in a very poor and highly
ramidus was a vertical upper jaw region. The braincase is quite fragmented condition. In particular,
good climber low and rounded. The teeth appear to be adapted Ardi’s teeth and the bones of its face
to a varied diet, with relatively small canines and were widely scattered across the
molars and an enamel thickness between that of excavation site.
chimpanzees and Australopithecus afarensis.
ARMS AND HANDS The upper arm bones flexible
(humeri) from at least seven Ardipithecus finger
ramidus individuals are known. The relative joints
proportions of the arms to legs is similar to
that seen in living monkeys such as macaques, long, curved
which tend to walk on all fours along fingers
branches. The finger bones of A. ramidus
pelvis has mix of are long, but the bones of the palm are short
features useful for and robust and the wrist is flexible. These
both climbing and characteristics are consistent with clambering
in the trees, which places a good deal of
upright walking loading on the hands, but not with the
femur (thigh knuckle-walking seen in modern apes.
bone)
ARDI HAND flexible wrist
tibia (shin bone) It is rare for the small bones of the hand and foot joint
to be preserved in fossil specimens, and these
finds help establish how our ancestors made the
transition from climbing to walking on two legs.
splayed big toe LOWER BODY The feet of Ardipithecus ramidus
for grasping retained an abductable (opposable) big toe, which
branches permitted grasping, combined with a robust and
supportive mid-foot and heel that allowed for
bipedal walking. The arms and legs are similar in
length, which might suggest arboreal clambering,
but the upper pelvis shows at least partial
adaptation to upright walking. The stature and the
body mass may seem large for a female, but it is
thought that there was little sexual dimorphism in
Ardipithecus ramidus.
toe bone ARDI FOOT
arrangement gave This well-preserved foot is particularly useful
firm forefoot for determining how Ardipithecus ramidus
moved, and shows an interesting mix of ape
and human traits, such as an opposable big
toe and a supportive mid-foot.
ARDIPITHECUS RAMIDUS 071
Ardipithecus ramidus:
In an area of open woodland, one individual forages in
the trees for fruit and nuts while others rest and eat.
EVIDENCE FOR DIET
Scientists have been able
to determine the diet of
Ardipithecus ramidus by
analyzing the thickness and
molecular content of its
tooth enamel. Evidence
suggests that it did not eat
abrasive foods but had a
mixed diet dominated by
woodland-based fruit, nuts,
and leaves, and possibly
including insects, eggs, and
small mammals.
UNIQUE HANDS
The hands and wrist of
Ardipithecus ramidus were
very different from those of
chimpanzees. Rather than
being adapted for knuckle
walking, they were better
suited to supporting weight
on their palms when moving
around in trees. This implies
that the last common
ancestor of chimpanzees
and humans did not move
like modern apes, as was
assumed by experts.
STANDING TALL
The construction of the
pelvis and feet support the
idea that Ardipithecus
ramidus could comfortably
stand and walk around.
Nevertheless, it is thought
that the walking style would
have been less energy
efficient than that of the
australopithecines, and it is
likely that the ability to run
would have been limited.
ASSOCIATED TREE LIFE
ANIMALS Analysis of its hand, arm,
Although there is no direct feet, pelvis, and leg fossils
evidence of Ardipithecus has revealed that
ramidus being preyed upon, Ardipithecus ramidus would
many of the fossilized bones have been comfortable
of mammals found in the moving around in trees.
same soil layer as “Ardi” However, they probably
show evidence of rodent did not swing between
gnawing and carnivore branches like modern
chewing—probably by gibbons, or climb vertically
hyenas, which certainly like chimpanzees, but
existed in this habitat. clambered about the
branches supported on their
feet and palms.
FAMILY GROUPS
Comparisons between the
teeth of male and females
have suggested that there
was little difference in body
size between the sexes.
This may indicate that
there was a low level of
competition between males,
and that some tasks such
as food gathering and child
care could have been taken
on by both sexes.
Australopithecus anamensis
The remains of this hominin have a combination of Physical features tooth enamel is thicker
characteristics found in modern apes and humans, and than in earlier apelike
it is likely that it could both walk upright and climb trees. The skull is known only from ancestors
fragments, but the jaw appears
AUSTRALOPITHECUS ANAMENSIS Discovery narrow and forward facing, with long, teeth arranged in parallel
parallel rows of teeth. The incisors and rows—an apelike
NAME MEANING “Southern ape Most of the Australopithecus canine teeth protrude, and the chin characteristic
from the Lake” anamensis fossils so far described recedes markedly. The ear canal is
come from Kanapoi and the Lake narrow, more like that of chimpanzees
AGE 4.2–3.9 mya Turkana Allia Bay site, Kenya. Since than modern humans. Overall the
1965, these sites have revealed the molars are modest in size with thick
HEIGHT Unknown remains of several individuals, but enamel, but tooth size varies between
all the fossils are fragmented. In individuals. These characteristics
BRAIN SIZE Unknown 1994, the species was defined using suggest a diet of fruits, seeds, and
KNM-KP29281, a jaw and ear canal, leaves. A shinbone, forearm, and
LOCALITY Lake as the type specimen. Other equally finger bone show evidence for weight
Turkana and fragmented remains have been found bearing on the legs, but also on the
Kanapoi, Kenya; in Aramis, the Middle Awash, and arms. The extent of bipedalism in
Aramis in Middle the Omo Basin in Ethiopia. Although A. anamensis remains hotly debated.
Awash and Omo some anthropologists support this
basin, Ethiopia species, others are less confident PARTIAL JAW
that the range of variation among KNM-KP29283 is a maxilla (upper jaw) with
FOSSIL RECORD Jawbone, teeth, the fossils can be accounted for teeth, found in 1994 in Kanapoi, Kenya, and
fragmented arm, thigh, finger bones in a single species. dated to 4.15 million years ago. The bone
below the front teeth slopes backward
rather than projecting forward.
DESERT DIG
Excavating for hominin fossils is a slow
and painstaking progress. Here, soil dug
up at Allia Bay, Kenya, is carefully sieved
through a fine mesh to make sure that
small fragments of bone that might have
been missed by excavators are recovered.
Australopithecus bahrelghazali
Australopithecus bahrelghazali is known from a sparse Physical features
fossil record, but its find-spot—1,550 miles (2,500km)
west of the Rift Valley—makes it an important find. The type specimen (KT12/H1) is the front part of an adult lower jaw with an
incisor, two canines, and four premolars. The anterior part of the jaw is quite
AUSTRALOPITHECUS Discovery deep and wide, with large canines compared to modern humans, and overall
BAHRELGHAZALI the specimen most closely resembles Australopithecus afarensis in size and
NAME MEANING “Southern ape Across most of Chad, Pliocene proportions (see p.79). Some subtle traits have been used to distinguish it
from Bahr el Ghazal” sediments are hidden by a thick layer from that species, however, including the presence of premolars with three
AGE 3.6–3 mya of later Quaternary deposits, and roots and relatively thin enamel. Whether this specimen is a regional variant
HEIGHT Unknown therefore fossils relating to the earlier of Australopithecus afarensis or a separate species, it is important because
BRAIN SIZE Unknown period are rare and discovered only it demonstrates that early hominins had a much wider geographical
LOCALITY Bahr el occasionally through bore holes. distribution than previously thought.
Ghazali, Chad However, in the region of Bahr el
Ghazal lies an ancient riverbed where receding jawbone incisor
FOSSIL RECORD Partial lower Pliocene sediments are exposed.
jawbone and teeth In 1993, a research team led by large
French paleontologist Michel Brunet canines
discovered a range of fossil
vertebrates here, including a partial ABEL JAW
hominin lower jaw (KT12/H1) with The jaw, known as “Abel”
seven teeth intact. Correlations with after the finder’s former
collections of faunal species from colleague Abel Brillianceau, is
other well-dated sites suggests a the only fossil currently known
date for this fossil of 3.6–3 MYA. from this species. Because
not many people have had
the chance to study it yet, its
significance for hominin
evolution remains unclear.
Kenyanthropus platyops
The nearly complete fossil skull that was found in 1999 Physical features
could provide evidence of a flat-faced hominin living
alongside Australopithecus afarensis. The type specimen is KNM-WT 40000, a largely complete cranium that
was distorted by geological processes. The size of the skull is within
KENYANTHROPUS PLATYOPS Discovery the australopithecine range, but the mid-face is flatter. The large cheekbones
have a forward position, and the hard palate is wide, but
NAME MEANING “Flat-faced man By the 1990s, it was clear that the nasal opening is narrow and the earhole is small.
of Kenya” several hominin species existed at There are few teeth preserved, but one molar is
AGE 3.5–3.3 mya any one time in the past. The period unusually small, and the enamel is quite thick.
HEIGHT Unknown 4–3 MYA was the exception to this, Cranial capacity is difficult to judge because
BRAIN SIZE Unknown with only Australopithecus afarensis of the distortion, but based on other
LOCALITY recognized in the fossil record. To measurements, Leakey suggested it was
Lomekwi in find out whether other species had within the range of Australopithecus
Nachukui existed alongside A. afarensis, or Paranthropus.
Formation, Kenya paleontologist Meave Leakey led a
team surveying sites in a fossil-rich although badly
FOSSIL RECORD Skull, upper jaw, region west of Lake Turkana, Kenya.
and teeth They collected fossils from several deformed, skull
individuals, including the distorted
cranium KNM-WT 40000, and the shows a brow
upper jaw KNM-WT 38350. Described
in 2001, Kenyanthropus platyops DISTORTED EVIDENCE ridge with flat
supports the view that more than one Paleoanthropologists face below
hominin species was living 3–3.5 MYA.
disagree as to whether this
badly distorted skull is
sufficiently well preserved to
be safely interpreted as
indicative of an entirely new poor state of skull
genus living alongside the makes teeth hard
australopithecines. to study
KENYANTHROPUS PLATYOPS 075
Australopithecus
afarensis
It is thought that Australopithecus afarensis could
be the ancestor of the genus Homo, to which
modern humans—Homo sapiens—belong.
Australopithecus afarensis is one of the best known of small braincase indicates short and low
a small brain forehead
the early hominins. The fragmented remains of several hundred
individuals, including males, females, and juveniles, have been found in lower face
East Africa. Research on this material has revealed evidence for both projects forward
terrestrial and arboreal lifestyles, and extreme sexual dimorphism.
receding chin
Discovery
SKULL AND TEETH The large face has wide
The Afar “triangle” in Ethiopia, where three tectonic cheekbones and a long nasal region narrowly
plates meet, is well known to geologists. In the 1970s, the separated from the mouth. The orbits are close
region became equally well known to anthropologists, together and the braincase is narrow behind the
because a number of extraordinarily rich fossil localitites eyes. The lower face and tooth row project
were discovered there. In 1973, American anthropologist forward, while the long upper canines are
Donald C. Johanson made the first of his many hominin separated from the incisors by a gap into which
finds at Hadar—two upper thigh bones, and a knee joint the lower canine fitted when the mouth closed.
that showed adaptations for upright walking. The team
published their finds the following year, at the same time
that Mary Leakey (see p.94) began excavating farther
south at Laetoli. Johanson and his team continued their
work in Ethiopia and soon discovered AL-288-1, a partial
skeleton dated to 3.2 million years ago and nicknamed
“Lucy.” In 1977 and 1980, American anthropologist Tim
White published descriptions of the Laetoli fossils found
since 1974, and in 1978 Johanson, Yves Coppens, and
White declared one of these specimens, the LH 4 adult
mandible, as the type specimen for their new species
Australopithecus afarensis. Over the past 20 years, many
more specimens have been discovered across the region,
including at Hadar, Maka, Aramis, and Dikika (Ethiopia),
Laetoli (Tanzania), and west Lake Turkana (Kenya).
FOSSIL HUNTER
The team led by Donald Johanson (far left) found the
first Australopithecus afarensis skeleton, which they
christened Lucy. Later, the remains of the “first
family” were discovered—13 individuals of the same
species who may have died together in a flash flood.
AUSTRALOPITHECUS AFARENSIS DIKIKA BABY UPPER BODY The arms of Australopithecus
afarensis were longer than those of modern humans.
NAME MEANING “Southern ape from Afar” sediment The arm bone to thigh bone ratio is similar to that of
filled in skull today’s baboons, and relative to body size the arm
LOCALITY Laetoli, Tanzania; White cavity during bone has a large cross section, which could suggest
Sands, Hadar, Maka, Belohdelie, fossilization the use of the arms for support. The fingers are longer
and Fejej, Ethiopia; Allia Bay and and curved, like those of orangutans. However, the
West Turkana, Kenya jaw retains milk curvature of the ribs suggests a thorax that was more
teeth and shows barrel shaped than in modern apes, and although the
8 MYA PRESENT AGE 3.7–3 mya vertebrae have relatively small surface areas, it is likely
7 MYA signs of tooth that the upper body was held erect.
6 MYA Dated mainly through eruption
1 MYA LUCY
Between 2000 and 2003, a partial The specimen catalogued as AL-288-1 is
absolute dating of skeleton of an infant A. afarensis nicknamed Lucy, after the Beatles song Lucy in the
volcanic ash layers above was recovered from deposits dated Sky with Diamonds, which was playing while the
2 MYA and below the fossils to 3.3 million years ago at Dikika, archaeologists celebrated their discovery. At the
Ethiopia. The dentition and bone time, Lucy was the most complete fossilized hominin
5 MYA 3 MYA maturity suggest an age at death skeleton known. However, she was not immediately
of about 3 years. The infant has recognized as a separate species and was only
4 MYA long, curved fingers that raise more later assigned to Australopithecus afarensis.
questions about the importance of
FOSSIL RECORD Partial adult skeleton; nearly complete arboreal behavior in this species.
baby skeleton; complete knee joint; limb fragments and
other bones; several mandibles and partial crania
078 HOMININS
small, low braincase Physical features
lower jaw projects Australopithecus afarensis is known from the remains of several hundred
forward individuals, representing most parts of the skeleton. The braincase is small
compared to the body size, but the face and jaws are large. The thorax has
an erect posture, and the shape of the legs suggests the species could walk
upright, while other features such as the length of the arms suggest good
climbing abilities. This group of fossils includes very large and very small
individuals and there is debate as to whether this variation reflects the presence
of two species, or one in which males and females have very different body size.
powerful arms suggest HEIGHT Males 5 ft (1.51 m); Females 3 ft 5 in (1.05 m)
that A. afarensis was a WEIGHT Males 93 lb (42 kg); Females 64 lb (29 kg)
good climber BRAIN SIZE 23–33 cubic in (387–550 cubic cm)
more funnel-shaped
ribcage than that
of modern humans
KADANUUMUU
Until 2005, Lucy was the only partial shoulder blade neck
Australopithecus afarensis skeleton similar to that of bones
known that included both upper and modern humans
lower limbs. But in January of that
long forearms year, Ethiopian fossil hunter Alemayehu
Asfaw, part of a team led by Yohannes
mobile wrist similar Haile-Selassie, discovered another upper clavicle
to modern apes example at Korsi Dora vertebrate arm
locality 1, in Ethiopia’s Afar region. rib cage is less
This find opened up a fresh chapter forearm cone-shaped
in our understanding of the species. than Lucy’s
This skeleton—dated to 3.58 million
short, broad pelvis enables thigh bone angles years ago and known as Kadanuumuu, pelvis suggests leg
A. afarensis to walk upright in toward the knee, or “big man”—is important because muscles attached in
allowing A. asfarensis it provides new evidence of stature,
short thighs like to balance on its hind limb proportions, and locomotion in the same way as
those of apes legs for long periods A. afarensis. Anthropologists have in humans
suggested that Kadanuumuu was
wide and notch on knee cap much larger bodied than Lucy, and lower part
weight-bearing allows well-balanced probably a male. Although his lower of thigh
limbs are rather short in comparison bone
knee joint standing to some later hominins, in many
respects his skeleton presents
stable ankle joint LOWER BODY Compared to modern adaptations associated with effective
humans the legs of A. afarensis are short, but upright walking. Even the shoulder
the thigh bones are angled and the cross blade, or scapula—which is a rare
section of the upper part of this bone is large. find in the fossil record—shows little
The short, broad pelvis articulates with a evidence for hanging in the trees or
lower spine that is less curved than our own. vertical climbing. The shape of the
The ankle and foot bones suggest a flatter, ribs suggests that the thorax was
more mobile foot, but with shorter and less less funnel shaped than previously
opposable toes than in modern apes. assumed, and the legs are angled
under the body to improve balance.
SKELETON OF A BIG MAN unusually long
The skeleton of Kadanuumuu is missing its shin bone
skull and teeth. Because these elements
are some of the most crucial for as with Lucy,
establishing to which species a specimen the ankle
should be assigned, some people disagree
with its identification as Australopithecus resembles that
afarensis. However, at the moment most of a human
researchers agree that Kadanuumuu is a
close relative of Lucy and the Dikika baby.
AUSTRALOPITHECUS AFARENSIS 079
Archaeology upper part of joint
angles towards the
Hominin fossils are not the only source of information about the ancient hip, indicating
past. The archaeological record also includes many other kinds of upright walking
physical evidence, such as stone tools, processed materials, animal
and plant remains, and changed landscapes. Paleoanthropological top of shin bone
fieldwork is a collaborative process in which experts in all these is widened to bear
disciplines come together to interpret a site and the finds within it. more weight, an
Two examples of this are the study of footprints and animal remains. essential feature
for bipedalism
FAMILIAR FOOTPRINT Preserved footprints
The Laetoli footprints preserve evidence of COMPLETE KNEE JOINT
the way the afarensis individuals’ bodyweight Having first visited Laetoli in 1935, Mary Leakey returned in 1974 to It is very rare that both
was distributed through their feet while begin a new phase of survey. The project generated many new fossil parts of the knee joint
walking. Taken together with the evidence of finds, including the type specimen for Australopithecus afarensis, but are preserved in a fossil
the foot bones, the prints demonstrate how perhaps the most exciting discovery was a series of remarkable specimen, and this find
similar their gait was to our own, rather than footprints. Sandwiched between layers of volcanic ash dated to 3.6 has given us valuable
to that of a chimpanzee walking upright. million years ago, these had been made by many species of animals, information on how
including elephants, giraffes, and hominins, walking in wet ashfall that A. afarensis walked.
subsequently hardened. The hominin tracks appear to have been made
by two individuals, one larger than the other, with a probable third individual
walking behind. Ever since their discovery, these Laetoli footprints have
been at the heart of the debate about the way in which early hominins
walked. Some anthropologists have pointed out the slightly divergent big
toe, reflecting a more mobile foot than seen in modern humans. Others
emphasise the deeper heel and toe impressions, reflecting a heel-strike
and toe push-off similar to modern walking.
STEPS BACK IN TIME
Australopithecus afarensis is not the only
species whose footprints are preserved
by the volcanic ash at Laetoli. Visible in
the top right of the image (opposite) are
prints made by an extinct type of
three-toed horse called Hipparion.
MODERN WALKING STYLE Evidence of early tool use
An experiment in 2009 compared 3-D contour profiles The first evidence for stone-tool technology appears in East Africa around marks A1 and A2
of the Laetoli footprints (above, bottom) with prints 2.5 million years ago, but in recent years archaeologists have discovered may have been made
made by humans using two different gait patterns: a indirect evidence for the use of stone tools as early as 3.39 million years ago. by a sharp-edged
normal extended-limb gait (top) and a bent knee, bent stone tool
hip, apelike gait (middle). The toe-relative-to-heel depths In 2009, the Dikika Research Project team conducted an archaeological
of the Laetoli prints were similar to those of the modern
human extended-limb prints. This is strong evidence survey of locality DIK-5, in the Lower Awash Valley, Ethiopia. This region was
that walking with an upright, humanlike gait developed
within the first 3 to 4 million years of hominin evolution. already known to have a rich fossil record, and was famous for the find of
a nearly complete juvenile Australopithecus afarensis specimen, DIK-1-1
(the “Dikika Baby”). During the course of the survey, two fossil ungulate
bones, a partial large rib, and a smaller thigh bone fragment were
identified with unusual surface modifications. Closer scrutiny
using state of the art imaging technology showed that the
marks were made before fossilization, possibly by a stone
tool’s cutting edge and a hammerstone. Some scientists
view the location of the marks as evidence that
hominins were removing flesh from the leg and mark B mark C
thorax, and also crushing the bones to remove
marrow. No associated stone tools were found, marks A1 and A2
and the claims remain highly controversial.
BUTCHERED BONE?
It has been suggested that marks A1 and A2
may have been made by a cutting tool, and
marks B and C by a hammerstone. If true,
this would put the date for the earliest known
tool use back by about 1 million years.
VOLCANIC ERUPTION
The Sadiman volcano is
located some 12 miles (20km)
east of the site where the
Laetoli footprint tracks were
laid down. It was very active
3.6 million years ago, and
frequent eruptions had
formed a conical-shaped
profile. Today, the volcano is
long extinct and its slopes
are greatly eroded.
SIZE DIFFERENCES
Some scientists suggest that
Australopithecus afarensis
exhibited a strong degree
of sexual dimorphism—size
differences between the
sexes—while others
suggest that differences
in body size may indicate
different species. The
Laetoli footprints were
probably made by
individuals of different sizes
walking together.
Australopithecus afarensis:
A small group walks through a desolate landscape
leaving tracks of footprints in recently fallen volcanic ash.
MYSTERIOUS FIGURE
Although it is clear that
the tracks were made by
two individuals walking
side-by-side, many of the
larger footprints forming the
right-hand track appear
blurred. Some scientists
suggest that this distortion
could have been created by
a third individual stepping in
the tracks of the larger
individual ahead.
ASSOCIATED
ANIMALS
The habitat of this part of
East Africa was similar to
that existing today, and so
it is not surprising that the
animal life was also similar.
More than 20 species of
savanna-based animals
left their tracks alongside
Australopithecus afarensis,
including giraffes, antelopes,
rhinoceroses, buffalo, and
elephants. The gigantic
Deinotherium is shown here.
FOOTPRINT
FORMATION
The Laetoli footprint tracks
were formed by a specific
sequence of events. An
initial eruption left a fine
layer of powdery ash
through which the hominins
left their mark. A soft rain
shower, followed by
sunshine, had the effect of
solidifying this layer, before
subsequent eruptions
covered the tracks until they
were eventually unearthed.
INCHES00 SIDE RIGHT
some development of
a bony crest along the hair probably
top of the skull straight and black,
as in modern
01 African apes
02 prominent brow
ridges above
the eyes
nose would
have been
wide and flat
with nostrils
facing
forward
Reconstruction deep lower
jaw lacks a
This reconstruction of an adult male was based on distinct chin
pieces of skull and jaw found among a group of fossils
known as the “first family,” which was made up of 17
individuals of various ages. This hominin had a distinctly primitive appearance
when compared to later Homo species, and it retained many characteristics
of our Miocene ape ancestors. Its braincase was very small and it had a wide,
dish-shaped upper face with a flat nose and forward-facing nostrils. As in
modern apes, its lower face was prognathic (with jaws that projected outward).
084 HOMININS
FRONT RIGHT FRONT
dark pigmentation would upper face
probably have protected relatively flat
skin from fierce African sun and broad
FRONT LEFT
nose and mouth cheekbones
separated by projected out wide
beyond the eye
deep upper lip sockets
SIDE LEFT skull housed a small
brain barely larger than
that of a chimpanzee
lower face and jaws huge jaw muscles
project forward, as attached to the skull
in modern apes AUSTRALOPITHECUS AFARENSIS 085
jaws relatively
long and
narrow
Australopithecus
africanus
The first early hominin species to be identified,
Australopithecus africanus firmly placed the
location of ancient hominin evolution in Africa.
Australopithecus africanus was the RAYMOND DART
species that proved fossil hominins were present Raymond Arthur Dart was born
in Africa. Its discovery showed that, despite having in Queensland, Australia, in 1893.
small brains, early hominins could walk upright. After studying biology at the
University of Queensland and
Discovery medicine at the University of
Sydney, he traveled to England to
Although Charles Darwin had argued that human origins probably lay in serve in the Medical Corps during
Africa, until the late 1920s fossil hominins had only been found in Europe and World War I. In 1923, Dart took
Asia. All this changed in 1924, when a box of fossils and rocks was sent to the position of Professor of
Raymond Dart, the Professor of Anatomy at South Africa’s Witwatersrand Anatomy at the University of
University. The collection had come from the Buxton limeworks at Taung, Witswatersrand in Johannesburg.
on the edge of the Kalahari Desert. Dart was a skilled neuroanatomist and A year later, he identified the
recognized that one of the specimens was an unusual primate “endocast,” oldest infant hominin skull ever
or natural cast of a braincase. It matched a partial juvenile skull, and with its found—the “Taung child.” Stung
vertical forehead, smooth brow, and slender bones, Dart quickly concluded by criticism of his work and the
that it represented an “extinct race of apes intermediate between living rejection of his claims about
anthropoids and man.” In 1925, Dart named this species Australopithecus Australopithecus africanus, Dart’s
africanus. Since then, many other fossils have been found in cave deposits at paleoanthropological activity
Sterkfontein and Makapansgat, including nearly intact skulls and skeletons. waned. He died at the age of 95,
having lived to see his views on
the Taung child vindicated.
AUSTRALOPITHECUS AFRICANUS
NAME MEANING “African southern ape”
LOCALITY Limestone caves
in Sterkfontein, Makapansgat,
Taung, and Gladysvale,
South Africa
8 MYA PRESENT AGE 3.3–2.1 mya
7 MYA
6 MYA 1 MYA Dated through relative
dating based on matching
fossils found in caves with
2 MYA fossils from absolutely
dated sites in East Africa
5 MYA 3 MYA
4 MYA STERKFONTEIN CAVES
These caves, northwest of Johannesburg,
FOSSIL RECORD Several partial skulls, a number of are among the most important fossil
jawbones, various skeleton fragments sites known. They have produced finds
of australopithecines, paranthropines,
and early Homo. The caves are now
a UNESCO World Heritage Site.
Physical features SKULL The skull of Australopithecus
africanus is rounded and lightly built.
While many of the specimens are fragmented or distorted, nearly all parts of The brain volume, at around 27 cubic in
the skeleton are represented by the Australopithecus africanus fossil record. (450 cubic cm), is similar to the mean
The evidence suggests a hominin of modest body size, capable of upright values of modern great apes, but the
walking, with a pattern of growth and maturation more similar to modern apes cranial vault is domed and the muscle
than humans. Some adult skulls appear to have been much larger (Sts 19) markings are faint. The neck-muscle
than others (StW 505), which may indicate differences between the sexes and attachments are low on the back of the
perhaps a haremlike social organization similar to that seen in modern gorillas. skull, which sits on a vertical spine. On
Alternatively, this variability in skull size may represent two different groups. the face, the brow ridge is modest and
the cheekbones are thin, but the upper
HEIGHT Female: 3ft 7in (1.10m); Male: 4ft 5in (1.35m) jaw is broad and projecting. The front
teeth are correspondingly large, and the
WEIGHT 55–110 lb (25–50 kg) canines show slight sexual dimorphism.
BRAIN SIZE 26–38 cubic in (428–625 cubic cm) TAUNG CHILD
Australopithecus africanus closely
resembled A. afarensis, but had a larger
jaw and strong cheekbones to support
the chewing muscles. The cheek teeth
were also bigger, but resembled those
of humans more than earlier hominins.
UPPER BODY The relatively long arms, gracile domed
the mobile shoulder, and long, large hand cheekbones braincase
bones indicate a load-bearing upper
body. Australopithecus africanus was
probably an adept climber, and would
have held its trunk upright when feeding.
broad upper jaw
rib cage would have “MRS. PLES” brain size
been cone shaped, The most complete skull (Sts 5), similar to that
as in apes found by Robert Broom at Sterkfontein of modern apes
in 1947, was initially classified as a
six lumbar Plesianthropus transvaalensis female
vertebrae in lower (hence its nickname). It is now thought
back, which is to have belonged to a young male.
sometimes seen in
LOWER BODY Like Australopithecus modern humans TAUNG CHILD
afarensis, the pelvis, femur (upper leg),
and foot bones of Australopithecus skull has a mixture
africanus indicate that it could comfortably of human and
walk bipedally. However, the toes are
long, and the foot is more mobile than apelike features
that of modern humans, with a flexible
arch and a more divergent big toe. The first molar teeth REMAINS OF BRAINS
lower vertebrae of the spine also have were found to be During fossilization, the child’s skull
smaller suface areas than in modern erupting in the jaw filled with sediments saturated with
humans, perhaps suggesting a calcium-rich water. The sediments
different range of motion or hardened into stone, preserving a
weight-bearing capacity. perfect replica of the inside of the skull.
pelvis adapted for bipedalism, The Taung child was the first A. africanus fossil to be found, and it is the type
but less rounded than in specimen for the species. Assessing the age of death in extinct species is
modern humans difficult since the rate of growth and maturation is unknown, but comparisons
with living primates provide clues. The Taung child retains all its milk teeth,
PELVIS AND SPINE and the first permanent molars are just erupting. This pattern appears at about
The pelvis and spine (Sts 14) of A. 6 years in humans and about 2–3 years in great apes. Microscopic analysis
africanus found at Sterkfontein by Robert of the tooth enamel and bone formation rates suggest a more apelike
Broom in 1947 indicated that the species pattern, so the Taung child is likely to have been 2–3 years old when it died.
was bipedal, and challenged the idea that
our ancestors’ brains grew significantly
before they walked on two legs.
AUSTRALOPITHECUS AFRICANUS 089
INCHES00 SIDE RIGHT
Taung child has no
significant brow ridges
while even young apes
show some bony ridges
over the eyes
01
02
Reconstruction jaw does not project very
far, although this may be
Although Australopithecus africanus shared many similarities with later because the Taung child
Homo species, it may be more closely related to the paranthropines. was so young; this feature
This reconstruction is based on the skull of the Taung child, who is thought develops quite late in apes
to have died aged about 2–3 years old between 2.5 and 2 million years ago. This
skull already shows many of the species’ key traits, but distinctively “apelike”
features often develop during growth in modern apes, and young apes look
more like humans than adults do. So the Taung child must be compared with adult
specimens in order to reach firm conclusions about the species’ characteristics.
090 HOMININS
FRONT RIGHT FRONT
A. africanus’s face is distance between
shorter and more the eyes is narrow
humanlike than that cheekbones not very
of A. afarensis wide in this juvenile
specimen, but
FRONT LEFT broader in adults of
the same species
SIDE LEFT
smaller, rounder Taung child’s lower
jaw and a greater jaw contained a full
set of milk teeth and
reliance on the its first permanent
back chewing molars in the process
teeth relative to
the front teeth of erupting
AUSTRALOPITHECUS AFRICANUS 091
Australopithecus garhi
Found in association with grassland and scrubland Physical features
animal species, this hominin is a candidate ancestor
for early Homo. Australopithecus garhi was a hominin of modest body size. There is some
evidence that it had longer legs than any of the other australopithecines,
AUSTRALOPITHECUS GARHI Discovery suggesting a more Homo-like walking mode. At the same time, it appears
NAME MEANING “Surprising that the arms were longer, and more robust, than in later hominins. Running
southern ape” In 1990, a team led by anthropologists along the midline of the braincase was a crest of bone, suggesting that
AGE 2.5–2.3 mya Berhane Asfaw (Ethiopia) and Tim A. garhi had strong chewing muscles. Long-bone size is variable, which
HEIGHT Unknown White (USA) recovered hominin fossils could suggest sexual dimorphism (difference between the sexes). Some
BRAIN SIZE 27 cubic in (450 cc) from the Bouri Formation in the anthropologists have remarked that the cranial characteristics are similar
LOCALITY Middle Middle Awash River Valley, Ethiopia. to those of A. africanus (see p.88).
Awash River Valley A mandible that retained tooth roots
in Afar, Ethiopia suggested, surprisingly, that although U-shaped
quite large and dating to around tooth row
FOSSIL RECORD Skull and jaw 2.5 MYA, this was not Paranthropus
fragments aethiopicus. In 1996–98, more PROJECTING JAW extremely large
remains were found at Bouri. These The face projects markedly, back teeth
included parts of the arms and thigh particularly at the front of the upper
bones of two to three individuals, jaw. It has slightly divergent dental
and a partial skull (BOU-VP-12/130) rows that hold a set of large teeth
that showed a distinctive suite of with thick enamel.
characteristics and which became
the type specimen for a new species
Australopithecus garhi—the “surprise.”
Paranthropus aethiopicus
The first fossil hominin to be found in Ethiopia, but Physical features
now best known from Kenyan sites, this species
shows a remarkably robust skull. Paranthropus aethiopicus is known almost exclusively from teeth and
skull fragments. Like the other paranthropines, it has small canines and
PARANTHROPUS AETHIOPICUS Discovery large molars that wear flat, which may suggest a poor-quality diet requiring
NAME MEANING “Ape that lived tough chewing. Unlike other paranthropines, the back tooth rows are long
alongside humans, from Ethiopia” The first hominin species to be found and parallel, and the front teeth are wide. The face tends to be large,
AGE 2.7–2.3 mya in Ethiopia was uncovered in 1967 projecting, and slightly dished (concave) in profile. Behind the modest
HEIGHT Unknown and named Paraustralopithecus brow ridge, the skull narrows and the cranial capacity is small, at around
BRAIN SIZE 25 cubic in (410 cc) aethiopicus. This partial jawbone, 25 cubic in (410 cubic cm).
LOCALITY Lake without teeth, did not make a huge
Turkana, Kenya; impact on anthropology at the time. distinct crest dish-shaped
Omo, Ethiopia Nearly 20 years later, at West Turkana mid-face
in Kenya, a team led by Kenyan
FOSSIL RECORD Two skulls, sections anthropologist Richard Leakey lower face
of jaw, and various teeth fragments uncovered the well-preserved projects
and distinctively wide-faced outward
“Black Skull.” By 1987, this was
grouped with the Ethiopian find as cheekbones THE BLACK SKULL
Paranthropus aethiopicus. Several positioned outward The best-preserved Paranthropus aethiopicus
other collections of fragmented jaws specimen is KNM-WT-17000, known as the
and teeth have also been ascribed to “Black Skull.” It has a dramatically wide face set
this species, including material from in front of a small braincase, and huge sagittal
the Shungura Formation in Kenya. crest for the attachment of chewing muscles.
092 HOMININS
Paranthropus robustus
A very robust hominin, the South African Paranthropus Physical features
robustus had massive back teeth and was well adapted
to a diet of tough or fibrous foods. Paranthropus robustus is known from
a collection of largely fragmented fossils.
PARANTHROPUS ROBUSTUS Discovery KROMDRAAI EXCAVATION Although probably modest in body size,
Kromdraai is a breccia-filled cave site with males rather larger and more robust
NAME MEANING “Robust ape that Paranthropus robustus was where Broom found the first P. robustus than females, they had distinctively wide
lived alongside humans” discovered at Kromdraai, South fossils. Together with other sites, such and slightly dished faces, with broad
Africa, by British-born paleontologist as Sterkfontein and Swartkrans, it is part cheekbones and a strong sagittal crest
AGE 2–1.2 mya Robert Broom in 1938. Broom had of a UNESCO World Heritage site. along the braincase—all features
purchased some fossil fragments associated with anchoring massive
HEIGHT 3 ft 7 in–4 ft 3 in (1.1–1.3 m) from locals and insisted on being chewing muscles to the skull and jaw.
shown the findspot. There he found
BRAIN SIZE 32 cubic in (530 cc) a very robust braincase, face and OVERSIZED TEETH
jaw, ankle bone, and an elbow joint. The molars and premolars of P. robustus were
LOCALITY Convinced that these represented a huge and thickly enameled, often wearing flat.
Kromdraai, hominin outside of the direct human These adaptations would have allowed these
Swartkrans, lineage, he published the material as hominins to eat hard, fibrous foods.
Gondolin, Paranthropus robustus. Broom went
Drimolen, and on to excavate more robust fossils
Cooper’s caves in from Swartkrans between 1948–49.
South Africa More recently, the very well-preserved
skull of a female (DH7) was found at
FOSSIL RECORD Various skulls; jaw, Drimolen in 1992.
teeth, and skeleton fragments
Australopithecus sediba
Australopithecus sediba may show part of the hominin Physical features
transition from arboreal locomotion to a more modern
pattern of bipedal walking. Australopithecus sediba is similar to the other australopithecines in its small
body size, long upper limbs, curved finger bones, and small brain size.
However, it also shares some features with Homo species. The face is narrow
Discovery compared to A. africanus, the brow ridge is modest, the lower jaw is quite
AUSTRALOPITHECUS SEDIBA In August 2008, nine-year-old pronounced, and the premolars and molars are relatively small. Functional
Matthew Berger found the collarbone
NAME MEANING “Southern ape of an immature australopithecine changes in the pelvis of A. sediba, such as increased bony buttressing
from the spring or well” while on site at Malapa, South Africa,
AGE 1.95–1.78 mya with his father, the American-born around the hip joint, point to the evolution
HEIGHT 4 ft 2 in (1.27 m) paleoanthropologist Lee Berger.
BRAIN SIZE 26–27 cu in (420–450 cc) Immediately focusing effort on of upright walking. The estimated high rounded skull
LOCALITY Malapa this findspot, the research team
fossil site (near unearthed two remarkable and rare strength of the femur (thigh bone)
Johannesburg), finds: the partial skeletons of a
South Africa juvenile male (MH1), and an adult indicates a strikingly humanlike
female (MH2). Publishing the material
FOSSIL RECORD Two partial in 2010, Berger named a new pattern of locomotion, and the
skeletons and numerous fragments australopithecine species because
the combination of characteristics level of sexual dimorphism
observed in the skeletons could
not be accommodated by any of (difference between the
the existing groups.
sexes) is similar to that
in modern humans.
MOSAIC OF FEATURES teeth similar in
This is the skull of a male size to those of
about 12–13 years old, with a Homo species
mosaic of primitive and more
recent characteristics that
shows a link between Homo
and australopithecines.
AUSTRALOPITHECUS SEDIBA 093
Paranthropus boisei
Paranthropus boisei, often nicknamed “nutcracker man,” LOUIS AND MARY LEAKEY
was a large parathropine with distinctive massive jaws
and cheek teeth, and very strong muscles and bones
associated with chewing. The species was sexually
dimorphic, with males much larger than females. Found
in East Africa, it seems that Paranthropus boisei was
successful and persisted for about 1 million years.
Discovery Louis Leakey was a Kenyan paleoanthropologist who became a curator of
the Coryndon Museum (later the Kenya National Museum) in Nairobi. In 1936,
After many years of fieldwork at Olduvai Gorge, Tanzania, Louis and Mary he married English archaeologist Mary Nichol. For nearly 30 years the pair
Leakey were rewarded with one of the key finds of their time: an extremely undertook joint excavations and surveys at Olduvai, describing the Oldowan
robust skull that defined a new species of hominin. When unearthed, the find tool industry (see p.102) and discovering the “Zinj” skull. From the 1950s,
revealed the near-complete cranium of an adult, including large teeth still Mary concentrated on the archaeology of Olduvai, while Louis became
articulated in the jaw. Catalogued as Olduvai Hominin 5 (OH 5), the new involved in other projects, such as primatological fieldwork in Africa and Asia.
specimen was named Zinjanthropus boisei (East African man) by Louis Leakey,
in recognition of both the findspot and the support of his sponsor, Charles for the “Zinj” site staggered the scientific community, demonstrating that the
Boise. Not only was this specimen the first of its kind to be found, but at the skull was around 1.75 million years old. Now placed in the Paranthropus
time it was also the earliest known hominin from East Africa. Pioneering genus alongside other robust hominin species, the specimen still dubbed
geochemical dating techniques were used on volcanic materials from the site “Zinj” retains a special place in the story of paleoanthropology.
to determine the geological age of the findspot; this had never been attempted
at a hominin-bearing site before. When this method, called potassium/argon
(K/Ar) dating, was first used at Olduvai most anthropologists thought that
human evolution stretched back only about half a million years. The results
PARANTHROPUS BOISEI
NAME MEANING Named after sponsor, Charles Boise
LOCALITY Olduvai and Peninj,
Tanzania; Omo Shungura
Formation and Konso, Ethiopia;
Koobi Fora, Chesowanja, and
West Turkana, Kenya
8 MYA PRESENT AGE 2.3–1.4 mya
7 MYA
Dated mainly from
6 MYA 1 MYA absolutely dated layers of
volcanic ash above and
2 MYA below the sediments
bearing the fossils
5 MYA 3 MYA
4 MYA SITE OF ORIGINAL FIND
A plaque marks the spot in Olduvai
FOSSIL RECORD Several well-preserved skulls and Gorge, Tanzania, where Mary Leakey
crania; many jaws and isolated teeth. No body or limb discovered the “Zinj” skull. She found a
fossils confirmed for this species jawbone during a routine site inspection.
The cranium was subsequently unearthed
and reconstructed from its fragments.
Physical features HEIGHT Males: 4 ft 6 in (1.37 m); Females: 4 ft (1.24 m)
Fossil skulls and teeth show Paranthropus boisei to have been a robust WEIGHT Males: 108 lb (49 kg); Females: 75 lb (34 kg)
species, characterized by a broad, long face, extremely large molar teeth,
and strongly developed bones of the braincase. P. boisei skulls are large BRAIN SIZE 29–33 cubic in (475–545 cubic cm)
relative to those of other early hominins, with a mean brain capacity of
31cubic in (508 cubic cm). Many anthropologists have noted that these NUTCRACKER MAN
characteristics are very similar to those of Paranthropus robustus (see P. boisei was nicknamed “Nutcracker
p.93), although they are typically more exaggerated in P. boisei. man” because of its powerful jaws and
large teeth. The skull resembles that of
CRANIUM The cranium of P. boisei is large, with P. robustus, but it is bigger and more
broad cheekbones and a robust maxilla (upper jaw). specialized for heavy chewing.
The eye orbits are rounded and very widely spaced,
surrounded by a pronounced brow region. The face is
relatively flat and slightly concave, and the whole skull
is short front to back, with strong attachment areas for
the neck and chewing muscles both on the base and
running along the top in a sagittal crest.
crest runs down the
center of the skull
cheekbones form
wide arches
TOP VIEW
Seen from above,
P. boisei’s huge, flared
cheekbones and narrow
braincase (especially just
behind the eye sockets)
are very apparent.
SEXUAL DIMORPHISM thick tooth enamel BODY AND LIMBS
Apart from skulls, very
All specimens of P. boisei share strongly built few fossils of other
certain key characteristics, but lower jaw skeletal regions are
some fossils are much larger than confidently ascribed to
others. At Koobi Fora, Kenya, lower face projects less than P. boisei. A small number
Richard Leakey (son of Louis and in other early hominins of skulls have associated
Mary) found a very large skull with noncranial fragments that
a sagittal crest and a smaller skull JAWS AND TEETH The upper and lower jaws (maxilla and suggest the body size
with a smooth, crestless cranium. mandible) are big and sturdy, to accommodate the huge molars and of this species varied
In modern gorillas, males have premolars that are among the largest found in any hominin species. substantially, and that the
a sagittal crest but the smaller The maxilla is wide and deep, while the mandible lacks a distinct femur was adapted for
females do not. So the larger chin, as in other early hominins. In many P. boisei specimens, the bipedalism. Until more
P. boisei skull with a crest was cheek teeth have been worn flat, which may indicate a diet that material is identified, the
probably a male, and the smaller included abrasive foods. In contrast to the rear teeth, the evidence is inconclusive.
one a female (see pp.96–97). incisors and canines are small. The canines have flat
wearing tips similar to the other teeth and do not vary small front teeth
significantly in size between specimens.
EVIDENCE OF DIET molars are among
Although the jaws and teeth could easily crush the largest of any
hard, brittle foods such as nuts and tubers, the hominin species
microscopic wear patterns on the teeth resemble
those of fruit-eating primates. P. boisei probably ate
nuts and tubers when its preferred food was hard to find.
PARANTHROPUS BOISEI 095
MALE
PARANTHROPUS BOISEI
With a length of 10 1⁄2 in
(27 cm), this male’s head is
significantly larger than the
female’s, which is 8 1⁄2 in (21 cm) long.
This robust head is reconstructed from
the OH 5 skull found at Olduvai Gorge.
096 HOMININS
FEMALE PARANTHROPUS BOISEI
This reconstruction is based on the
KNM-WT 17400 cranium that was
found in West Turkana, Kenya.
It was from a female P. boisei who
lived 1.7 million years ago.
Sexual dimorphism and tooth size that were at least as high as in gorillas, and
this probably represents sexual dimorphism. P. boisei females,
Sexual dimorphism describes the degree of physical therefore, may have been much less heavy and muscular than the
difference between adult males and females of the same males. Homo ergaster shows a much lower level of sexual dimorphism,
species, in addition to the sex organs. Among the primates similar to that seen in modern humans. In gorillas, the high level of sexual
dimorphism is often seen in body size, shape, and coat color. Some species, dimorphism has been associated with competition between males, with one
such as gibbons and modern humans, show little sexual dimorphism while male controlling access to females. As P. boisei fossils show a similar range of
others, such as modern gorillas, are highly dimorphic, with males weighing physical differences, they may also have experienced male-male competition.
up to twice as much as females. Many early hominins, such as Paranthropus
boisei, were characterized by levels of variation in body weight, muscle mass,
PARANTHROPUS BOISEI 097
Homo habilis
This species was named Homo habilis, meaning
“handy man,” because some of its fossils are
associated with early stone tools.
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