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August 10, 2007
The Ileret Skulls
I haven't written on paleoanthropology for a while. I've been too tightly focused on things that I am finally beginning to know something about again. But a recent paper is getting so much attention that I cannot just ignore it.
Afarensis has a good summary of the paper by F. Spoor and a host of others including Meave and Louise Leakey. His post has lots of links to other blogs and news accounts. The controversy, as far as there is one, revolves around two recently discovered fossils that Mike Dunford of The Questionable Authority characterizes as follows:
One of the fossils, a cranial dome that's been identified as belonging to a young Homo erectus, has been dated at about 1.55 million years old. The other, a partial upper jaw from Homo habilis, is about 100,000 years younger (1.44 million years old).
Shocking, a Homo habilis jaw 100,000 years more recent than a Homo erectus cranial dome. At least you'd think it shocking from some of the press accounts afarensis and others cite. Well, it is only shocking if you are stuck on anagenesis as the only explanation of human evolution. But it shouldn't surprise anyone that predecessors of our species overlapped chronologically. Cladogenesis is clearly part of our evolutionary history. Afarnisis spells it out complete with a nice chart showing cladogenesis at the Homo habilis - Homo erectus split. Kimbel, Johanson, and Rak first published this chart in 1977!
Here's the abstract of the paper under discussion:
Sites in eastern Africa have shed light on the emergence and early evolution of the genus Homo. The best known early hominin species, H. habilis and H. erectus, have often been interpreted as time-successive segments of a single anagenetic evolutionary lineage. The case for this was strengthened by the discovery of small early Pleistocene hominin crania from Dmanisi in Georgia that apparently provide evidence of morphological continuity between the two taxa. Here we describe two new cranial fossils from the Koobi Fora Formation, east of Lake Turkana in Kenya, that have bearing on the relationship between species of early Homo. A partial maxilla assigned to H. habilis reliably demonstrates that this species survived until later than previously recognized, making an anagenetic relationship with H. erectus unlikely. The discovery of a particularly small calvaria of H. erectus indicates that this taxon overlapped in size with H. habilis, and may have shown marked sexual dimorphism. The new fossils confirm the distinctiveness of H. habilis and H. erectus, independently of overall cranial size, and suggest that these two early taxa were living broadly sympatrically in the same lake basin for almost half a million years. [Citations removed]
Abnormally interesting and like many scientific discovers this tends to provide support for one longstanding hypothesis against another longstanding hypothesis. It says absolutely nothing about the underlying theory of evolution. For me, the most interesting suggestion in the paper is the possibility, even probability, that "these two early taxa were living broadly sympatrically in the same lake basin for almost half a million years."
Posted by Duane Smith at August 10, 2007 9:37 AM | Read more on Paleoanthropology |
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Comments
The chart did not come from Kimbel, Johanson and Rak. Sorry I gave that impression.
Posted by: afarensis at August 10, 2007 3:22 PM
Afarensis,
I inferred what you did not say. Upon rereading your post, I see that you did not explicitly say the chart was from Kimbel, Johanson, and Rak. Sorry. Where is it from? I Like it a lot.
Posted by: Duane at August 10, 2007 3:43 PM
It is from here
Posted by: afarensis at August 10, 2007 7:55 PM
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