The Earliest Dispersal of the Genus Homo: Homo erectus and Contemporaries

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Chapter 9

• The Earliest Dispersal of the Genus Homo Homo
  erectus and Contemporaries

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Left Homo Erectus (1mya)Center
Australopithicus afarensis (2.5mya)Right Homo
Neandertalensis (100,000-32,000ya)
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BECOMING HUMAN PART II

• NOVA

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First Dispersal of the Hominins

• Close to 2 million years ago, hominins expanded
  out of Africa into other areas of the Old World.
• Since the early hominin fossils have been found
  only in Africa, it seems that hominins were
  restricted to this continent for as long as 5
  million years.

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First Dispersal of the Hominins

• After 2 mya, theres less diversity in these
  hominins than in their pre-australopith and
  australopith predecessors.
• There is universal agreement that the hominins
  found outside of Africa are members of genus
  Homo.
• Homo erectus is the species for which there is
  the most evidence.

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Homo erectus A New Kind of Hominin

• The first hominin to expand into new regions of
  the Old World.
• As a species, H. erectus existed over 1 million
  years.
• We can understand its success as a hominid
  species based on behavioral capacities (i.e.)
  more elaborate tool use) and physical changes
  (i.e. larger).

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Homo erectus

• Discoveries from East Africa have established
  Homo erectus by 1.8 m.y.a.
• Some researchers see anatomical differences
  between the African and Asian discoveries.
• They place African fossils into the Homo ergaster
  species.
• Analyses show that H. erectus/ergaster represents
  closely related species and possibly geographical
  varieties of a single species

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Grade

• H.erectus hominins represent a different grade of
  evolution than their African predecessors.
• Grade refers to a grouping of organisms sharing a
  similar adaptive pattern.
• Grade implies nothing directly about shared
  ancestry, but implies general adaptive aspects
  of a group of animals

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Morphology of Homo erectus

• Living in different environments over much of the
  Old World, H. erectus populations shared several
  common physical traits including

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Body Size

• Adult weight gt100 lbs, average adult height of
  ca. 5 feet 6 inches
• Sexually dimorphic, weight and height varied
  according to sex
• Increased robusticity (heavily built body) that
  dominated hominin evolution until anatomically
  modern H. sapiens

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Brain Size
?Homo Sapien Skulls?

• Cranial capacities 700 cm3 to 1250 cm3
• Brain size closely linked with overall body size
• H. erectus is larger-bodied than early Homo
  sample but relative brain size is about the same
• Relative brain size of H. erectus is considerably
  less encephalized than later members of genus Homo

 1. Australopithecus afarensis   2.
Australopithecus africanus  
3. Homo habilis   4. Homo erectus 5. Homo
Neandertalensis
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Cranial Shape

• Thick cranial bone, large browridges
  (supraorbital tori), and projecting nuchal torus
• Braincase long and low, with little forehead
  development
• Cranium wider at base, compared with earlier and
  later species
• Sagittal keel, a small ridge from front to back
  along the sagittal suture, reflects bone
  buttressing in a very robust skull, rather than a
  specific function

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Homo Erectus findsAfrica, Asia, Indonesia, Europe
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Homo erectus from Africa

• Homo erectus evolved first in Africa, supported
  by evidence of
• Earlier hominins prior to the appearance of H.
  erectus occurring in Africa.
• 1.8 mya fossils at East Turkana, in Kenya, and
  not long after at other sites in East Africa.
• Though, 1.75 mya populations in southeastern
  Europe 1.6 mya populations in Indonesia,
  suggesting quick migrations

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TURKANA BOYa.k.a. Nariokotome Skeleton WT 15000

• In 1984, Kamoya Kimeu discovered a small piece of
  skull on the west side of Lake Turkana at the
  site known as Nariokotome.
• The excavations produced the most complete H.
  erectus skeleton ever found
• Facial bones, a pelvis, and most of the limb
  bones, ribs, and vertebrae.

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TURKANA BOYNariokotome Skeleton

• The Nariokotome skeleton is dated to about 1.6
  mya.
• The skeleton is that of a boy about 12 years of
  age with an estimated height of 5 feet 3 inches.

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Olduvai Gorge

• Find by Louis Leakey in 1960, includes
  well-preserved cranial vault with small part of
  upper face.
• Dated at 1.4 mya, the cranial capacity is the
  largest of all the African H. erectus specimens.
• The browridge is the largest known for any
  hominin, but the walls of the braincase are thin.
  
• Similar to East African H. erectus specimens
  differs from thick cranial bones in Asian H.
  erectus.

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Gona Evidence

• Ethiopia find dated to appx. 1.3 mya
• Female pelvis with very wide birth canal,
  indicating large-brained infants in utero
• Perhaps newborn H. erectus with a brain that was
  comparable to typical modern human baby
• Suggests, when compared with Nariokotome pelvis,
  considerable sexual dimorphism in skeletal
  anatomy is linked to reproduction and body size

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Daka Evidence

• Middle Awash of Ethiopia find dated to appx. 1
  mya
• Complete cranium more like Asian H. erectus than
  most earlier East African remains discussed
• Discounts argument that East African fossils are
  different species than Asian H. erectus

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