Gracial Australopithecines

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Gracial Australopithecines
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Australopithecus from East Africa

• East African fossil remains assigned to the genus
  Australopithecus (or in some cases, Paranthropus)
  date from 4.2 to 1.4 m.y.a.
• The genus Homo appears near the end of this time
  span.
• The earliest Australopithecus remains come from
  Allia Bay and Kanapoi (4.2-3.9 m.y.a.).

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Scientific Evidence

• Australopithecines
• Evolved 5-3 million years ago in Africa
• The ape that stood up
• Characteristics
• Bipedal
• Small brain size
• Relatively small body size
• Between 3 and 4 feet
• 60-100 pounds

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Bipedality Evidence
Female Gorilla
Australopithecus africanus
Modern Humans
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Australopithecus anamensis

• Named in August 1995.
• The material consists of 9 fossils, mostly found
  in 1994, from Kanapoi in Kenya, and 12 fossils,
  mostly teeth found in 1988, from Allia Bay in
  Kenya.
• Dates to 4.2 and 3.9 mya,
• mixture of primitive features in the skull
• and advanced features in the body.
• The teeth and jaws are very similar to those of
  older fossil apes.
• A partial tibia (the larger of the two lower leg
  bones)
• evidence of bipedality
• and a lower humerus (the upper arm bone) is
  extremely humanlike.

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Australopithecus anamensis
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Australopithecus afarensis (ca. 3.5mya)
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Lucy

• Discovered by Donald Johanson and Tom Gray in
  1974 at Hadar in Ethiopia.
• Its age is about 3.2 million years. Lucy was an
  adult female of about 25 years.
• About 40 of her skeleton was found, and her
  pelvis, femur (the upper leg bone) and tibia
  show her to have been bipedal.
• She was about 107 cm (3'6") tall (small for her
  species) and about 28 kg (62 lbs) in weight.

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Australopithecus afarensis from Laetoli and Hadar

• The material from Laetoli and Hadar (fragmentary
  remains of 60-100 individuals) constitutes the
  largest and best-studied assemblage of early
  hominids.
• Except for A. anamensis, A. afarensis is the most
  primitive member of its genus.
• The canines are large, the lower first premolar
  is semisectorial, the tooth rows are parallel,
  there is a compound crest on the back, and the
  cranial base is primitive.
• The cranial capacity averages about 420 cm3.

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• The postcranial remains
• upper limbs, relative to the lower limbs, are
  longer than expected when compared to modern
  human proportions.
• Height ranges from 36 to about 5 tall.
• If we accept that the taller individuals are
  male, then A. afarensis has a large degree of
  sexual dimorphism in body size
• though this conclusion has been recently
  disputed.
• Despite the many primitive dental and cranial
  traits, it is clear that A. afarensis is a
  hominid because it was a biped when on the ground
  (although A. afarensis may have retained
  significant climbing capabilities).

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Another East African hominid

• Contemporaneous with A. afarensis (at 3.5
  m.y.a.), was discovered at Lake Turkana in 1999.
• The 400-500 cm3 cranium has a flat face and small
  molars.
• This is not an A. afarensis pattern, so it has
  been given a new genus name, Kenyanthropus.

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Kenyanthropus platyops

• Discovered by Justus Erus, a member of a team led
  by Meave Leakey, in 1999 at Lomekwi in Kenya
  (Leakey et al. 2001, Lieberman 2001).
• Estimated age is between 3.5 and 3.2 million
  years.
• This is a mostly complete cranium which came in
  two pieces
• a skullcase which was heavily distorted
• face which was much better preserved.
• The fossil has an unusual combination of
  characteristics, most notably a flat face and
  small teeth.
• The name means Flat faced man of Kenya.

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Australopithecus bahrelghazali 3.0 and 3.5 mya
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Diagnostic Features

• Discovered in 1996 by Michel Brunet et al.
• Dated by associated fauna to between 3.0 and 3.5
  mya.
• Ancient riverbed of Bahr el Ghazal in Chad, 2,500
  kilometers west of the Rift Valley.
• This was the furthest west australopithecine
  material had been found in Africa.
• The type specimen is a mandible retaining seven
  teeth
• The features of the mandible that differentiate
  it from most of the afarensis material include
• The mandibular symphysis is much more vertical on
  its interior surface behind the incisors and the
  premolars (more closely resembling the modern
  form than afarensis.

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Australopithecus africanus (ca. 3 mya)
STS 5  Ms. Ples Discovered by Robert Broom in
1947 at the South African site of Sterkfontein
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• First discovered by Raymond Dart in 1925.
• He found a beautifully preserved skull of a
  juvenile, three to four years old.
• Commonly known as the Taung Child,
• Taung South Africa where it was found, is perhaps
  the best preserved fossil of A. africanus known.
• Astralopithecus africanus has a somewhat dish
  shaped facial structure with teeth that are
  relatively large compared to modern humans.
• While it has larger front teeth compared to the
  back the emphasis is on back tooth grinding.
• As a result, a sagital crest is present on males
  for the attachment of large muscles.
• This species is rather lightly built and has a
  small cranial capacity of about 440 cc on the
  average.
• It first appeared approximately 2.5 million years
  ago and had a rather short 1 million year
  existence.

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Taung Child
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Pelvis-Comparisons
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Australopithecus garhi
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• Named in the April 23, 1999.
• Bouri Formation, Ethiopia, and have been dated to
  approximately 2.5 mya.
• Set of cranial fragments comprising the frontal,
  parietals, and maxilla with dentition.
• The specimen was discovered on November 20, 1997,
  and the word garhi means "surprise" in the local
  Afar language.
• These specimens are important no matter what the
  eventual final attribution, due to the fact that
  the remains are from East Africa at a time when
  there is very little remains (2.0-3.0 mya).

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• A. garhi is distinguished unique combination of
  dental and facial features.
• The cheek teeth are absolutely larger than
  Australopithecus afarensis, and can be said to be
  "megadont".
• However, A. garhi lacks derived characters of the
  robust early human lineage, leaving it as a
  sister taxon to the gracile forms.
• The morphology of the face retains primitive
  characteristics of A. afarensis.
• The cranial capacity of the partial skull has
  been estimated at 450 cc.
• under such Australopithecine individuals such as
  Mrs. Ples but slightly larger than modern
  chimpanzee capacities
• However, aspects of the dentition are very
  similar to early specimens of the genus Homo.
• Postcranially, the A. garhi material shows
  human-like ratios for femur to humerus length
  while retaining ape-like proportions for the
  length of the forearm to the upper arm (the
  brachial index).

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Limb-Comparisons

• On the left is a diagram comparing the upper
  (first two rows) and lower limb bones of a
  chimpanzee (Pan), "Lucy," a form of A. afarensis,
  BOU-12/1, the bones which may belong to A. garhi,
  KNM-WT-15000, an early form of H. erectus, and
  Homo (modern).
• The BOU-12/1 limb bones, if they do belong to A.
  garhi, indicate a move away from the earlier
  australopithecine pattern, where the forearms
  were long compared with the leg bones, and a move
  toward a more Homo like pattern.
• Homo erectus, who first appeared in the
  evolutionary record some 1.7 - 1.8 million years
  ago, had shortened forearms and longer legs, much
  like modern humans.
• The new limbs bones ball right in the middle the
  leg bones are longer than the earlier
  australopithecines, although the forearms are
  still long.

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Tool Users?

• Bones of a number of large animals, such as
  antelope, were discovered near the fossils
  displaying evidence of cut marks from stone
  tools.
• While this evidence of butchery suggests an
  important shift in dietary habit and the first
  use of stone tools by hominids, no tools were
  found in direct association with the fossil
  finds.