EARLY HOMININS

hominins

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  • Created by: Jo Gandon
  • Created on: 14-05-09 22:39

HOMININ CHARACTERISTICS

Characterised by THREE main features: (bdb)

  • LARGE brain relative to their body size
  • advanced dentition with rotary chewing
  • adaptations to bipedal locomotion
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HOMININ GENERA TIME LINE

The hominin and African ape lineage split about 6-8 million years ago.

6-7 million years ago: Sahelanthropus

6 million years ago: Orrorin

4.4 million years ago: Ardipithecus

3.9 -1.2 million years ago: Australopithecus / Paranthropus

3.5 million years ago: Kenyanthropus

2 million years ago - present: Homo

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EXPLANATIONS FOR HUMAN EVOLUTION

  • Formation of the East African Rift Valley about 6-8 million years ago
  • Conditions became drier and more open
  • The forest became replaced with Savannah

THUS

Humans are apes adapted to an open habitat BUT many early hominids are at least partially arboreal.

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Sahelanthropus tchadensis

  • 6 - 7 million years ago
  • had an extremely large, robust supraorbital torus (brow ridge)
  • the cranium was similar to that of a gorilla
  • its hominin status was defined by its "smaller canines with apical wear" (M. Brunet, 2002)
  • many others suggest a closer relationship to gorillas or chimpanzees
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Orrorin tugenensis

  • 5.6 - 6.2 million years ago
  • also known as "the millenium man" as it was discovered in 2000
  • its hominin status was defined by its femur, in particular its muscle attachment on the femoral neck
  • many have argued that it is an agile climber but walked on 2 legs on the ground
  • howevr, many are still not convinced by this e.g. B. Senut et al (2001)
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Ardipithecus ramidus

  • 4.4 million years ago
  • its toe bone shows that it may have walked bipedally
  • its teeth also suggest hominin status with projecting canines and hominin-like wear patterns which suggest rotary chewing
  • long powerfully muscled arms
  • no knuckle-walking features
  • no hindlimb material
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THE GRACILE and ROBUST hominins

The GRACILE hominins are:

1) Australopithecus anamensis (3.9 - 4 mya)

2) Australopithecus afarensis (2.8 - 3.4 mya)

3) Australopithecus bahrelghazeli (3 - 3.5 mya)

The ROBUST hominins are:

1) Australopithecus africanus (3.2 mya)

2) Australopithecus gahri (2.5 mya)

3) Australopithecus Paranthropus aethiopicus (2.6 - 2.2 mya)

4) Australopithecus Paranthropus boisei (2.3 - 1.2 mya)

5) Australopithecus Paranthropus robustus (2.1 - 1.2 mya)

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