Five Peculiar Fossils

Colin Barras of The New Scientist has a very short, very peculiar article on five hominin fossils that have been used to define new species and addresses the validity of each in very cursory fashion.  The strength of the article is in the links that it provides.  About Sahelanthropos, he writes this:

Features at the skull’s rear suggest it sat atop a vertical spine like that of a human, hinting that S. tchadensis walked upright. To make sure, other fossils will be needed – particularly from the legs. Unconfirmed reports suggest that a thigh bone was found with the skull, but this has not yet been discussed in a scientific paper. With so little evidence to go on, some are sceptical that S. tchadensis can really yet be defined as a hominin rather than some other form of ape – yet.

These are the least of its problems, as it is likely a surface find. Aside from this, when Wolpoff and colleagues examined the cranial base, here is what they found:

The prominence of the nuchal muscles, so important in head balance and loading, and shoulder movements, is enhanced by the significant development of the tuberculum linearum. The point is not that the TM 266 cranial rear and posterior portion of the cranial base was unlike hominids because the region looks like apes, but that TM 266 had a posture that is not upright because the region reflects nuchal functions similar to those of apes.

The foramen magnum - orbit plane angle does not directly address posture or locomotion in these hominoid primates (contra Zollikofer et al., 2005). Without a key postcranial element such as a pelvis or femur, none of these data provide compelling evidence for upright posture or obligate bipedal locomotion, and the various details of the nuchal plane argue against it. This functional implication has a phylogenetic consequence—by itself it is sufficient to disprove the phylogenetic hypothesis that TM 266 was a hominid.

This isn't skepticism. This is the door slamming shut.  It can be a surface find and still be a Miocene ape. In my recent piece for BioLogos, it did not occur to me to include this fossil since there are so many problems with it.  At this point, in Africa, the earliest reasonable evidence we have for hominins is Orrorin tugenensis. 

Read the whole (short) thing.

Oldest Human DNA Recovered

Using the fossil material from the Sima de Los Huesos cave, at the Spanish site of Atapuerca, geneticists have recovered DNA.   From the National Geographic story by Karl Gruber:

Analysis of the bones challenges conventional thinking about the geographical spread of our ancient cousins, the early human species called Neanderthals and Denisovans. Until now, these sister families of early humans were thought to have resided in prehistoric Europe and Siberia, respectively. (See also: "The New Age of Exploration.")

But paleontologists write in a new study that the bones of what they thought were European Neanderthals appear genetically closer to the Siberian Denisovans, as shown by maternally inherited "mitochondrial" DNA found in a fossil thighbone uncovered at Spain's Sima de los Huesos cave.

"The fact that they show a mitochondrial genome sequence similar to that of Denisovans is irritating," says Matthias Meyer of Germany's Max Planck Institute for Evolutionary Anthropology in Leipzig, lead author of the study, published Wednesday in Nature.

"Our results suggest that the evolutionary history of Neanderthals and Denisovans may be very complicated and possibly involved mixing between different archaic human groups," he said.

Although the report argues that the Atapuerca remains show a greater similarity to Denisovans than Neandertals, we already know that modern Europeans and East Asians have Neandertal genes in them, indicating that admixture was occurring.  Milford Wolpoff has been arguing for decades that archaic Homo sapiens represents a polytypic species that has genetic ties to modern human groups in different parts of the Old World.  While it certainly appears that Neandertals were distinctive, this information, in conjunction with various studies (here and here) of the Denisovans and African archaics indicates that this model may be the more correct one. 

Lost in the shuffle, however, is that the ability to recover this DNA is an astounding feat of science and portends for great advances in human palaeontology in the future.