The Earliest Hominins

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The Earliest Hominins
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When?

• genetic evidence suggests hominins originated
  between 5 7 mya
• unfortunately...
• fossil record of hominoids in Africa is sparse
  from 8 to 4.5 mya

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• Predictions?
• equatorial Africa
• 7-5 mya
• size between gibbon and chimpanzee
• principally arboreal, not exclusively
• preference for upright posture
• some bipedalism, in trees ground
• some knuckle-walking (later lost) ?
• prognathic cranium
• large molars, thickly enameled

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Oldest known hominins

• Sahelanthropus tchadensis Chad 6-7
• Orrorin tugenensis Kenya 6
• Ardipithecus kadabba Ethiopia 5.8
• Ardipithecus ramidus Ethiopia 4.4
• Australopithecus anamensis Kenya 4.2-3.8
• Australopithecus afarensis Ethiopia 3.6-2.9
• Australopithecus bahrelghazali Chad 3.5-3.0
• Kenyanthropus platyops Kenya 3.5
• Australopithecus garhi Ethiopia/Kenya 2.5
• Australopithecus boisei Malawi---Ethiopia 2.3-1.4

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Toros- Menalla
Lomekwi
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Sahelanthropus tchadensis

• Nickname Toumaï
• hope of life in the Goran language
• Discoverer Ahounta Djimdoumalbaye
• Location Toros-Menalla fossiliferous area,
• Djurab Desert, Northern Chad, 2001

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Toros-Menalla
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Michel Brunet comparing tchadensis and chimpanzee
skull.
Toros-Menalla hominid site
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Ahounta Djimdoumalbaye, L, with Michel Brunet.
Ahounta Djimdoumalbaye, center, and colleagues.
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Dating

• Relative dating techniques
• faunal correlation compared Toros-Menalla site
  with two other locations in Kenya
• result Chad fossils 6-7 million years old
• Absolute dating techniques
• - no ash layer
• - sediment unsuitable for magnetism- based
  dating methods

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TM 266-01-060-1 Skull
TM 266-02-154-1 Jaw fragment
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Saggital crest
Wide intraorbital, large, thick, continuous
supraorbital torus
Small endocranial cavity 320-380cc
Orthognathic face
Compound temporal-nuchal crest
Slight subnasal prognathism
Long, narrow basicranium
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• oldest member of the hominin clade
• (interpretation controversial)
• early members of the hominin clade were more
  spread out geographically
• split between human and chimpanzee lineages
  occurred earlier than thought

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Orrorin tugenensis
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Orrorin tugenensis

• Martin Pickford and Brigitte Senut
• 2000
• Tugen Hills, N Kenya
• KAr dates 5.8-6.1 mya

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Ardipithecus ramidus kadabba

• Yohannes Haile-Selassie
• 2001
• Middle Awash River Valley, Ethiopia
• 5.2-5.8 mya, faunal correlation

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Ardipithecus ramidus

• Tim White
• 1994
• Aramis,
• Middle Awash,
• Ethiopia
• 4.4 mya

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Australopithecus anamensis

• Maeve Leakey
• 1994
• Kanapoi and Allia Bay, Kenya
• KAr 3.9-4.2 mya

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A. bahrelghazali
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Australopithecus bahrelghazali

• Michel Brunet
• 1995
• Bahr el Ghazal,
• Chad
• 3.0-3.5 mya
• faunal correlation

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Kenyanthropus platyops

• Maeve Leakey
• 1999
• Lomekwi, Kenya
• KAr 3.2-3.5 mya

K. platyops compared to H. habilis
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Leakey.com
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