The Biology of early Homo

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The Biology of early Homo

• In comparison to the australopithecines, the
  early members of the genus Homo possess
• 1. Molars and premolar are smaller in the
  bucco-lingual dimension (that is, the breadth of
  the tooth from inside to outside) than those of
  the australopithecines.
• 2. The mandible and maxilla are less massive
  with muscle attachment areas smaller and reduced
  in robustness.
• 3. Brain volumes vary (510 800ml.), but are,
  in general, larger and housed in a brain case
  with a higher, more rounded shape.

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Species of early Homo

• Based on differences in the size of the brain
  case as well as differences in posterior tooth
  size, a number of species of early Homo have been
  proposed
• 1. Homo habilis known from sites at Olduvai
  Gorge (Tanzania) and east of Lake Turkana
  (Kenya).
• 2. Homo rudolfensis east of Lake Turkana.
• 3. Homo erectus (or Homo ergaster) Olduvai
  Gorge, Lake Turkana, and South Africa.

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Homo habilis

• When established in 1964, considered to represent
  the evolutionary transition from the
  australopithecines to Homo.
• Name means handy person .
• Fossils are dated to 1.7 - 1.8 myr. Initially
  from Olduvai and now from East Turkana.
• H. habilis possesses a brain size of between
  580-650ml, larger than those of the
  australopithecines, but smaller than other
  species of early Homo.
• Homo habilis has less broad (B-L) cheek teeth
  than australopithecines.

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Type of Homo habilis OH-7

• OH-7, consisting of this mandible of an immature,
  associated with parts of both parietals, and
  postcranial bones (OH-8), was found in 1960 at
  FLK NN1.
• It is the holotype specimen of Homo habilis.
• Oldowan tools are associated with this find.

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Homo habilis

• OH-24, a paratype of Homo habilis, is the oldest
  fossil found at Olduvai Gorge.
• It was found at the site of DK1, and is dated to
  about 1.84myr.
• The Leakeys found a stone ring at this site,
  though not directly associated with this skull.
• Oldowan tools were also found here.

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Homo rudolfensis

• H. rudolfensis is dated to about 1.8 -1.9 myr.
  Term comes from the original name for Lake
  Turkana.
• The fossils possess very large brain volumes
  (750-800ml), but also very large,
  australopithecine-size molar teeth.
• Are the H. rudolfensis fossils the males, and the
  H. habilis fossils the females of a single,
  sexually dimorphic species?

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Homo erectus

• Earliest dated at east Turkana at 1.8-1.9 myr,
  and contemporary with the other early Homo
  species.
• Name was originally given to later-in-time
  fossils found in the last century in Java,.
• H. erectus possessed very large brains (800ml),
  like H. rudolfensis, but also reduced in size
  back chewing teeth, like H. habilis.
• H. erectus is the most reasonable of the early
  Homo species to be considered ancestor to later
  in time hominids (modern humans).

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The boy from Nariokatome

• Discovered in 1984, the skeleton, WT-15000, is
  that of an approximately 11-12 year old boy.
• Found eroding out from under the roots of a tree,
  up until the origins of deliberate burials,
  around 100,000 years ago, this is the most
  complete skeleton of our ancestors ever found
• The skeleton does not reveal how this child died,
  but it possesses some very interesting biological
  features, including a very tall stature, a brain
  of 800 ml, relatively small teeth, but
  robusticity that is greater than that of the
  presumed female, KNM-ER 3733.

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Evolutionary Relationships of Early Homo

• Early Homo evolved from one or another
  australopithecine species.
• There may be as many as three species of early
  Homo living at the same time in East Africa, with
  H. erectus (Homo ergaster) the most probable
  ancestor of later hominids.
• After 2.0 myr, stone tools are common, often with
  animal bones with scratch marks. This suggests
  butchery or scavenging of dead animals. It is
  unclear which early Homo species made the tools
  (or if a robust australopithecine was
  responsible).

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The First Out of Africa Expansion by Human
Ancestors

• Some possible explanations why early Homo left
  Africa and expanded into Eurasia include an
  increase in cultural complexity, or the breakdown
  of a barrier at the Suez bottleneck.
• This expansion out of Africa was to have crucial
  consequences.
• An important theory of modern human origins
  suggests that there was a later, second expansion
  out of Africa associate with anatomically modern
  humans.

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Earliest Sites in Eurasia

• Ubeidiya Site on the Jordan River in Israel, on
  a natural corridor out of Africa. No hominid
  fossils, but stone tools similar to those from
  East Africa (Oldowan), and many African mammal
  bones. Dated to about 1.5-1.6 myr.
• Dmanisi In the Republic of Georgia, the fossils
  are dated to about 1.5-1.7 myr.
• Perning Earliest of a series of sites on the
  island of Java (Indonesia). A childs skull is
  dated to 1.6-1.8 myr.

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Spread out of Africa

• Evidence suggests soon after the evolutionary
  appearance of H. erectus, hominids begin to
  spread out of Africa to regions in Eurasia.
• The reasons for this expansion are unclear. It
  may be related to the disappearance of a
  bottleneck at Suez, or to the increasingly
  complex cultural behavior of the hominids, which
  allowed them to a more diverse set of
  environments.

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Who spread out of Africa?

• Between 1.8 and 1.7 myr, currently the most
  reasonable times when the homs leave Africa, is
  also a period when there are perhaps five species
  of homs contemporary with each other in Africa
  (H. habilis, H. rudolfensis, H. erectus (H.
  ergaster?), Australopithecus (Paranthropus?)
  boisei and A. robustus.
• Were all of these species able to cross into
  Eurasia, which would argue for the disappearance
  of a barrier preventing animal movements across
  the Suez, or did only one species make it,
  arguing instead for some specific biological or
  behavior attributes that were present on only one
  of these species.
• For the moment, this question remains
  unanswerable.

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Whats in a Name?

• Thus far, we have been talking about the spread
  of Homo erectus out of Africa, but not all
  anthropologists agree that this is the right, or
  only. name for the hominids of this time.
• Some believe that Homo erectus is a term to be
  used only for the fossils from Asia, and that the
  earliest species in Africa ought to be called by
  another name, Homo ergaster.

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Homo erectus versus H. ergaster

• What is the difference in the diagnosis of these
  two species, and is it valid?
• 1. Homo erectus was established in 1894 for
  fossils from Java. Later discoveries in Java and
  China have been placed within this taxon.
• 2. Fossil discovered at Lake Turkana (KNM-ER
  3733, WT-15000) Initially suggested a very close
  affinity with the Asian fossils (I.e. Walker and
  Leakey describing 3733). It has been subsequently
  asserted that there was too much temporal and
  geographic distance between the two samples to
  place them all in a single species.
• 3. No morphological studies have demonstrated
  specific difference between the two samples.

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Homo erectus in Java

• First discovery by Eugene Dubois, who went to
  Java to find the Missing Link.
• After the initial discoveries by Dubois, many
  additional Homo erectus fossils have been found
  at a number of sites.
• When H. erectus lived on Java, the island was
  part of mainland Asia, connected because of the
  drop in sea levels brought about by glacial
  activity in the Northern Hemisphere.

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