Don Johanson Hadar, Ethiopia

Transcription

1 Don Johanson Hadar, Ethiopia Hadar Turkana Olduvai & Laetoli

2 Hadar Knee Joint Australopithecus afarensis Don Johanson,, 1973 Hadar,, Ethiopia Age: million years Significance: The distal femur and proximal tibia fragments articulate at an angle characteristic of bipedal hominids, rather than quadrupedal apes. This confirmed that the Hadar fossils were hominids.

3 Lucy (A.L. 288) Australopithecus afarensis Don Johanson,, 1974 Hadar,, Ethiopia Age: 3.2 million years Significance: The most famous fossil of our century, and the most complete specimen of any hominid this old. Three and a half feet tall and fully bipedal with a chimp- sized brain, Lucy represents Australopithecus afarenis,, the earliest well- described hominid species.

4 A.L. 333 First Family Australopithecus afarensis Don Johanson,, 1975 Hadar,, Ethiopia Age: 3.2 m Significance: Hadar location 333 yielded the remains of nine adults and four juveniles es (including the child shown above and many of the Hadar jaws at the right). If its discoverers are correct in their assumption that these individuals died together in a catastrophic event, the site offers a cross-section section of an afarensis population.

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6 Meanwhile: Laetoli fossils & prints

7 Dating Hadar Potassium-Argon Fission Track Paleomagnetism Biostratigraphy Lucy First Family

8 At first, Johanson shared Mary & Richard Leakey s Interpretation: Two types Lucy = primitive First family & Laetoli = Homo Evidence: Small molars Age of 1470 Homo is very old Lucy not our ancestor (See Leakey s s phylogeny in Origins)

9 Richard Leakey s Phylogeny in Origins (1977) H. sapiens 1 million years 2 million years 3 million years A. robustus Lucy? A. africanus H. erectus million years Homo sp. First Family Laetoli Footprints 5 million years?

10 Why did Johanson Change? Biostratigraphy? Date of KBS tuff? Allometry? If Lucy, First Family, & Laetoli are one, what are they? Not Homo!

11 How are hominid teeth different? Canine size & shape Canine dimporphism Diastema Canine and molar wear Dental arcade shape Premolar cusps

12 Hadar Teeth: Transitional Canine size & shape Canine dimporphism Diastema Canine and molar wear Dental arcade shape Premolar cusps

13 Don Johanson s Phylogeny in Lucy (1981) H. sapiens 1 million years A. robustus H. erectus 2 million years 1470 A. africanus H. habilis 3 million years 4 million years A. afarensis Lucy & First Family Laetoli Footprints 5 million years?

14 Richard Leakey s Phylogeny in Origins (1977) H. sapiens 1 million years 2 million years 3 million years A. robustus Lucy? A. africanus H. erectus million years Homo sp. First Family Laetoli Footprints 5 million years?

15 Don Johanson s Phylogeny in Lucy (1981) H. sapiens 1 million years A. robustus H. erectus 2 million years 1470 A. africanus H. habilis 3 million years 4 million years A. afarensis Lucy & First Family Laetoli Footprints 5 million years?

16 Species: Australopithecus afarensis Hadar + Laetoli fossils Fully bipedal Oldest hominid, 3-43 mya Smallest brain Extreme dimorphism Transitional dental morphology Common ancestor of other hominids

17 Don Johanson s Phylogeny in Lucy (1981) H. sapiens 1 million years A. robustus H. erectus 2 million years 1470 A. africanus H. habilis 3 million years 4 million years A. afarensis Lucy & First Family Laetoli Footprints 5 million years?

18 Johanson s reinterpretation of Australopithecines Robusts are younger Small molars ancestral (retained in Homo) Large molars a derived Australopithecus trait Relativity of ancestral & derived Graciles evolved into robusts

19 A Scientific Objection to Johanson Phylogeny One species or Hadar? Yves Coppens is among dissenters First family interpretation circular? Doubts linger

20 A. L Australopithecus afarensis Yoel Rak,, 1992 Hadar,, Ethiopia Age: 3 million years Cranial capacity: 500 cc Significance: This large male is the most complete adult afarensis skull yet. It has fueled both sides of the debate about the number of species at Hadar.

21 Next... Explaining Hominids