Bipedalism Gif animations by Andrew Mills
based upon E. Muybridge (1913), Athlete, Running,Child, Crawling
PLIOCENE HOMINIDS
WEB CREDIT: Many of the SPECIES DESCRIPTIONS from Week Six, Hominid skullduggery, and Week Eight come from Jim Foley's outstandingThe Talk.Origins website.
Ardipithecus ramidus: 4.4 MYA, East African Rift Valley (Aramis, Ethiopia). Found by Tim White from the Berkeley Institute for Human Origins in 1994. "Ardipithecus" means "ground ape"; "Ramidus" means root: the implication is that A. ramidus may be the root species which gave rise to all of the later hominids. Arms seem not to be those of a knuckle walker, and the base of the cranium suggests erect posture although it is not yet clear whether A. ramidus was bipedal. Still retains thin enamel. Cranium still very small and chimp-like.
Australopithecus anamensis: 4.2 - 3.9 MYA, East African Rift Valley (Lake Turkana). Found by Maeve Leakey in 1995. Anamensis means "lake" in a local Turkana language. Twenty-one specimens. Confirmed bipedalism. Specimens show a blending of primitive (large, ape-like canines) and advanced features (bipedalism and thick enamel). Cranium still very small and chimp-like.
Australopithecus afarensis: 4 - 2.5 MYA, East African Rift Valley and North Central Africa (Hadar, Ethiopia; Bahr el Ghazal, Chad; others). In 1975, a Berkeley team including Donald Johanson & M. Taieb found remains of a very complete hominid specimen near the Awash River in Hadar, Ethiopia ("Lucy"). Name comes from the Afar region of Ethiopia where the "Lucy" specimen was found. Dentition more similar to humans than to ancestral Miocene apes (reduced canines, more parabolic jaw shape), but still retains a slight diastema. Dentition most likely reflects an omnivorous diet without specialization in any one type of food resource. Cranium still very small and chimp-like. Postcranial remains indicate that A. afarensis was a habitual biped, but also retained upper body characteristics of brachiators - may have been practicing both forms of locomotion. Highly sexually dimorphic species.
The Taung Child (A. africanus).
Raymond Dart started the whole
thing off with THIS baby!
That's her fossilized brain on the left
Australopithecus africanus
Australopithecus africanus: 3.5 - 2.5 MYA, South Africa (Taung,
Sterkfontein and others). First Australopithecine to be identified
(Raymond Dart's Taung child, 1924).
Name means "southern ape of Africa." Dentition much more similar to
humans than to ancestral Miocene apes (canines reduced, more parabolic
jaw shape, no diastema).
Dentition most likely reflects an omnivorous diet without specialization
in any one type of food resource. Cranium still very small and
chimp-like. Postcranial remains
indicate that A. africanus was a habitual biped, but also retained upper
body characteristics of brachiators - may have been practicing both forms
of locomotion.
A. africanus is similar to afarensis, and was also bipedal, but body size was
slightly greater. Brain size may also have been slightly larger, ranging between 420 and 500 cc. This is a little larger than chimp
brains (despite a similar body size), but still not advanced in the areas necessary for speech. The back teeth were a little bigger
than in afarensis. Although the teeth and jaws of africanus are much larger than those of humans, they are far more similar to
human teeth than to those of apes (Johanson and Edey, 1981). The shape of the jaw is now fully parabolic, like that of humans,
and the size of the canine teeth is further reduced compared to afarensis.
Australopithecus afarensis and africanus are known as gracile australopithecines, because of their relatively lighter build,
especially in the skull and teeth. (Gracile means "slender", and in paleoanthropology is used as an antonym to "robust".) Despite
this, they were still more robust than modern humans.
Paranthropus boisei & P. robustus. Note the sagittal crest like Worf on Star Trek--able to chew and chew and chew . . .
Paranthropus boisei (was Australopithecus boisei)
Paranthropus boisei: 2.4 - 1.3 MYA, East African Rift Valley (Olduvai
Gorge and other sites). Discovered by Louis & Mary Leakey in 1959.
Originally named
"Zinjanthropus." Cranial features suited for heavy chewing and a diet of
hard foods (sagittal crest, flaring zygomatic arches, huge jaw, large
molars for grinding).
Cranium still very small and chimp-like. Considered the most "robust" of
the three robust species.
It was similar to robustus, but the face and cheek teeth were even
more massive, some molars being up to 2 cm across. The brain size is very similar to robustus, about 530 cc. A few experts
consider boisei and robustus to be variants of the same species.
Paranthropus aethiopicus, robustus and boisei are known as robust paranthropines, because their skulls in particular
are more heavily built.
Paranthropus robustus
Paranthropus robustus: 2 - 1 MYA, South Africa. Discovered by Robert
Broom in 1938. Name means "robust near-man." Cranial features suited for
heavy chewing and
a diet of hard foods (sagittal crest, flaring zygomatic arches, huge jaw,
large molars for grinding). Cranium still very small and chimp-like.P. robustus had a body similar to that of africanus, but a larger and more robust skull and teeth. It existed between 2 and 1.5
million years ago. The massive face is flat or dished, with no forehead and large brow ridges. It has relatively small front teeth,
but massive grinding teeth in a large lower jaw. Most specimens have sagittal crests. Its diet would have been mostly coarse,
tough food that needed a lot of chewing. The average brain size is about 530 cc. Bones excavated with robustus skeletons
indicate that they may have been used as digging tools.
Paranthropus aethiopicus: 2.6 - 2.3 MYA, East African Rift Valley (Lake Turkana, others). "Parathropus" means "near man." The first specimen ("Black Skull) was discovered by Richard Leakey in 1985. Cranial features suited for heavy chewing and a diet of hard foods (sagittal crest, flaring zygomatic arches, huge jaw, large, flat molars for grinding). Features seem to be mid-way between A. afarensis and the other robust types (P. boisei and P. robustus). Cranium still very small and chimp-like.
Homo habilis and Australopithicus africanus
So what do you want? They did their own dentistry.
Homo habilis
H. habilis, "handy man", was so called because of evidence of tools found with him. Habilis existed between 2.4 and 1.5
million years ago. It is very similar to australopithecines in many ways. The face is still primitive, but it projects less than in A.
africanus. The back teeth are smaller, but still considerably larger than in modern humans. The average brain size, at 650 cc, is
considerably larger than in australopithecines. Brain size varies between 500 and 800 cc, overlapping the australopithecines at
the low end and H. erectus at the high end. The brain shape is also more humanlike. The bulge of Broca's area, essential for
speech, is visible in one habilis brain cast, and indicates it was probably capable of rudimentary speech. Habilis is thought to
have been about 127 cm (5'0") tall, and about 45 kg (100 lb) in weight, although females may have been smaller.
Habilis has been a controversial species. Some scientists have not accepted it, believing that all habilis specimens should be
assigned to either the australopithecines or Homo erectus. Many now believe that habilis combines specimens from at least
two different Homo species.
Homo erectus (Java)
Homo erectus (China) & H.sapiens (for comparison)
There are "regional
varieties" of Homo erectus e.g. Africa, Asia, Java
Homo erectus
H. erectus existed between 1.8 million and 300,000 years ago. Like habilis, the face has protruding jaws with large molars, no
chin, thick brow ridges, and a long low skull, with a brain size varying between 750 and 1225 cc. Early erectus specimens
average about 900 cc, while late ones have an average of about 1100 cc (Leakey, 1994). Some Asian erectus skulls have a
sagittal KEEL (not Sagittal CREST). The skeleton is more robust than those of modern humans, implying greater strength. Body proportions vary; the
Turkana Boy is tall and slender, like modern humans from the same area, while the few limb bones found of Peking Man
indicate a shorter, sturdier build. Study of the Turkana Boy skeleton indicates that erectus may have been more efficient at
walking than modern humans, whose skeletons have had to adapt to allow for the birth of larger-brained infants (Willis, 1989).
Homo habilis and all the australopithecines are found only in Africa, but erectus was wide-ranging, and is found through Africa
and Asia (and was probably in Europe, but no unambiguous skeletal remains are known from there). There is evidence that
erectus probably used fire, and their stone tools are more sophisticated than those of habilis.
Cro-Magnon & Neandertal--dig those supra orbital ridges on the dude on the right!
Cro-Magnon was a modern Homo sapiens sapiens (see description below)
Homo sapiens neanderthalensis (was Homo neanderthalensis)
Neandertal man existed between 230,000 and 30,000 years ago. The average brain size is slightly larger than that of modern
humans, about 1450 cc, but this is probably correlated with their greater bulk. The brain case however is longer and lower than
that of modern humans, with a marked bulge at the back of the skull. Like erectus, they had a protruding jaw and receding
forehead. The chin was usually weak. The midfacial area also protrudes, a feature that is not found in erectus or sapiens and
may be an adaptation to cold. There are other minor anatomical differences from modern humans, the most unusual being some
peculiarities of the shoulder blade, and of the pubic bone in the pelvis. Neandertals mostly lived in cold climates, and their body
proportions are similar to those of modern cold-adapted peoples: short and solid, with short limbs. Men averaged about 168
cm (5'6") in height. Their bones are thick and heavy, and show signs of powerful muscle attachments. Neandertals would have
been extraordinarily strong by modern standards, and their skeletons show that they endured brutally hard lives. A large
number of tools and weapons have been found, more advanced than those of Homo erectus. Neandertals were formidable
hunters, and are the first people known to have buried their dead, with the oldest known burial site being about 100,000 years
old. They are found throughout Europe and the Middle East. Western European Neandertals usually have a more robust form,
and are sometimes called "classic Neandertals". Neandertals found elsewhere tend to be less excessively robust. (Trinkaus and
Shipman, 1992; Trinkaus and Howells, 1979; Gore, 1996)
The final stage in the evolution of bipedalism is Emily aka "Bigfoot"
Homo sapiens sapiens (modern)
Modern forms of Homo sapiens first appear about 120,000 years ago. Modern humans have an average brain size of about
1350 cc. The forehead rises sharply, eyebrow ridges are very small or more usually absent, the chin is prominent, and the
skeleton is very gracile. About 40,000 years ago, with the appearance of the Cro-Magnon culture, tool kits started becoming
markedly more sophisticated, using a wider variety of raw materials such as bone and antler, and containing new implements
for making clothing, engraving and sculpting. Fine artwork, in the form of decorated tools, beads, ivory carvings of humans and
animals, clay figurines, musical instruments, and spectacular cave paintings appeared over the next 20,000 years. (Leakey,
1994)
Even within the last 100,000 years, the long-term trends towards smaller molars and decreased robustness can be discerned.
The face, jaw and teeth of Mesolithic humans (about 10,000 years ago) are about 10% more robust than ours. Upper
Paleolithic humans (about 30,000 years ago) are about 20 to 30% more robust than the modern condition in Europe and Asia.
These are considered modern humans, although they are sometimes termed "primitive". Interestingly, some modern humans
(aboriginal Australians) have tooth sizes more typical of archaic sapiens. The smallest tooth sizes are found in those areas
where food-processing techniques have been used for the longest time. This is a probable example of natural selection which
has occurred within the last 10,000 years (Brace, 1983).
Acheulian Hand axes and Chopper Tools
Homo sapiens sapiens
Carpe Noctem!
© 1997 call0031@tc.umn.edu
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