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Monday, March 16, 2009

A New African Late Miocene Ape

Martin Pickford and colleagues recently announced the discovery of a fossil ape from Niger. Fauna from the site suggest an age of anywhere from 11 - 5 million years ago. The fossil is just a fragment of the right mandible, containing the roots of the first molar. The form of the molar roots show its affinities with hominoid primates. Aside from that, little can be said about the fragment. It is very slender, unlike any hominin. The authors note that the size of the jaw and aspects of the root ally it closely with modern chimpanzees, but it does not preserve any diagnostic features that link it specifically to any living or fossil ape.

You might think this does not sound like an important find, but I think it is. First, the African late Miocene has a poor hominoid fossil record. Exceptions to this are the mysterious, putative hominins Sahelanthropus, Orrorin, and Ardipithecus kadabba; and the ape-like Chororapithecus, Nakalipithecus, and Samburupithecus. So this new specimen, whether it represents one of the already-known fossil apes or is a new taxon, provides further evidence that apes were present in Africa in this time period. This bears on the debate about whether the living African apes (gorillas and chimpanzees/bonobos) originated in Eurasia or Africa, though certainly more fossils are needed to address this.

Second, most African fossil hominoids are known only from Eastern Africa. As such, it has looked like much of hominoid and hominin evolution have taken place there. At the moment, the only other non-East-African fossil hominoids I can think of are the 13 million year old Otavipithecus mandible from Namibia, and the 7 million year old Sahelanthropus fossils from Chad. So it is clear that hominoids (and hominins) existed in places other than East and South Africa. As the authors note, it is not unlikely that more hominoids (and hominins?) will be discovered in western and central Africa. Who knows, we might even get some (more?) chimpanzee ancestors out of it, which is something I feel paleoanthropology desperately needs.

Source:

Pickford M, Coppens Y, Senut B, Morales J, and Braga J. Late Miocene hominoid from Niger. Comptes Rendus Palevol In Press, Corrected Proof.


Thursday, March 12, 2009

Redating gives older age to Chinese Homo erectus

Paleoanthropology news so big, it makes the cover of the current Nature (left), albeit with a lame headline that says, "Peking Man was Cool." I know, lame, right? Like the editor was trying to be 'hip' and reach a new generation of nerds. Although 'cool' has been used since like the 1950s. And I peruse Nature, so it's not nerdy.

Anyway, yes, researchers working at the Zhoukoudian (aka Chokoutien, etc.) cave site in China have redated the Homo erectus-bearing layers. As is the problem with the South African cave sites from which we get some great Australopithecus fossils (and "Paranthropus," if you're so inclined), cave sites are difficult to date radiometrically, with absolute dates based on the decay of radioactive materials. Before now, Zhoukoudian had been dated to about 500-250 ka (thousand years ago). Such a date is roughly contemporaneous with some "archaic Homo sapiens" (whatever that really means) fossils, which are generally thought to be intermediate in morphology between Homo erectus and modern people such as you or I. Could this indicate the coexistence of Homo erectus and more 'modern' people?

Well, the site has now been dated to about 770 ka, plus or minus 80ka (Shen et al. 2009). This means that the hominin occupations at the site start at nearly 800 ka, and end around 400 ka. Does this older date mean that now the overall picture of human evolution is clear? Of course not. But, it does fit the same kind of pattern we see elsewhere. The new dates show that, like in other areas, older more classically erectus-like hominins predate more intermediate "archaic" forms of humans. Moreover, it's now certain that these fossils don't (at least not the older ones) overlap in time with younger, "archaic" humans, such as that from Jinniushan.

So I guess that's the main point, that the earlier dates of Zhoukoudian emphasize the fact that evolutionary trends in Asian middle Pleistocene hominins are the same as those throughout the world. If you really think that all these ancient regions represent separate species or distinct lineages, I suppose you could argue that this pattern of similarity means parallel evolution. A much more sensible interpretation, in my opinion, is that these populations were connected, even if only sporadically, by gene flow.

Sunday, March 1, 2009

What (academically) are you good at?

Another blog I read asked this question the other day. How you answer tells you a lot about how good you are at promoting yourself (a trait that will become very important as we advance in our careers and start job-searching, etc.). For example, if you preface your answer with "I think I'm good at..." you make yourself sound weak.

The blogger also noticed that very few professors in her experience would answer this question with "I'm a good teacher or mentor" - even if they had won awards in the past for teaching! I think how we answer this question says a lot about our views on academia and our place in it. If we believe research is the most important part of a professor's job, then of course we won't list "teaching" as one of our better skills for fear that doing so would make us look like we have nothing else to offer.

When I thought about how I would choose to answer this question, I realized my answer would change depending on whether my lab(and blog)mates were in the room. I apparently feel more comfortable building myself up as a researcher when people who have actually seen me research (or not) are not in the room. This shocked me and is making me re-evaluate what it is I'm good at.

These "tips" aren't news - we should all be capable of recognizing that qualifying our answer is a no-no. It's hard to admit that we are really good at something useful, and not just "getting by" or "messing around" or something. I encourage anyone who reads this to think about how they would answer this question (and if you feel comfortable, post your answer in the comments section so we can marvel at what wonderful readers we have!)