Saturday, 31 January 2015

The 55,000 year old anatomically modern human fossil from Israel: yet another nail into a well-hammered YEC coffin

It's been a good week for paleoanthropology. First, we've had the amazing discovery of a mandible off the cost of Taiwan of a mandible from a decidedly archaic member of the genus Homo. Now, Nature reports the discovery of a 55,000 year old anatomically modern human skull from Manot Cave in Israel. For those who still persist in denying the reality of human existence well before the earliest possible date for Adam and Eve, no amount of evidence will penetrate their dogmatism, but when discoveries like this accumulate in the minds of fair-minded members of our community, the dogmatists will find peddling their denialism increasingly more difficult.

So, what's the fuss about? From the abstract:
A key event in human evolution is the expansion of modern humans of African origin across Eurasia between 60 and 40 thousand years (kyr) before present (BP), replacing all other forms of hominids 1. Owing to the scarcity of human fossils from this period, these ancestors of all present-day non-African modern populations remain largely enigmatic. Here we describe a partial calvaria, recently discovered at Manot Cave (Western Galilee, Israel) and dated to 54.7 ± 5.5 kyr BP (arithmetic mean ± 2 standard deviations) by uranium–thorium dating, that sheds light on this crucial event. The overall shape and discrete morphological features of the Manot 1 calvaria demonstrate that this partial skull is unequivocally modern. It is similar in shape to recent African skulls as well as to European skulls from the Upper Palaeolithic period, but different from most other early anatomically modern humans in the Levant. This suggests that the Manot people could be closely related to the first modern humans who later successfully colonized Europe. Thus, the anatomical features used to support the ‘assimilation model’ in Europe might not have been inherited from European Neanderthals, but rather from earlier Levantine populations. Moreover, at present, Manot 1 is the only modern human specimen to provide evidence that during the Middle to Upper Palaeolithic interface, both modern humans and Neanderthals contemporaneously inhabited the southern Levant, close in time to the likely interbreeding event with Neanderthals 2, 3.
I've frequently referred to how mainstream scientists refer to evolution as fact, theory, and historical path. The first aspect refers to common descent and large-scale evolutionary change, both of which are no long doubted outside of a tiny, poorly-informed fundamentalist fringe whose motivations are not scientific but theological. The second refers to the theoretical mechanism proposed to explain the fact of evolution, while the third refers to the particular historical aspects of natural history, such as the date and timing of speciation events. 

It goes without saying that the fact of human evolution is not in doubt - the fossil and genetic evidence is beyond rational dispute, with human-ape common ancestry from genomic data and a trend towards increased cranial size and obligate bipedality clearly evidence in the fossil record. This finding offers zero support to creationist seeking to overturn the fact of human evolution. In fact, it provides yet more evidence to overturn their view that anatomically modern humans first walked on the planet 6000 years ago given that we have something securely dated to almost ten times that figure. What it does do is provide some insight on the details of the period between 45,000 to 90,000 years ago when anatomically modern humans moved out of Africa to Europe and beyond.

Source: Nature

There are some problems in that fossil sites in northern Israel such as Qafzeh and Skhul show Homo sapiens in the older levels, and Homo neanderthalensis in the younger levels. Nature News comments that the Manot Cave skull, which is younger and more modern-looking than the Skhul / Qafzeh skulls, may help provide answers to this question, but points out that in science, things are never cute and dried:
Here comes the ‘but’. Our modern genomes contain Neanderthal DNA. At some point, our ancestors bred with Neanderthals before they became extinct. Does the Manot skull represent that moment? We simply do not know. Welcome, Manot skull, to messy reality.
Physical anthropologist and Christian James Kidder, provides further informed commentary on the question of exactly when and how modern humans moved out of Africa into the rest of the world:
The authors seem to think that there was not continuous evolution from the Skhul/Qafzeh humans, which date to around 100k BP, to the population represented by the Manot Cave individual and that the Manot Cave 1 specimen represents a later migration of moderns into the area, although this is based largely on the fact that there aren't fossils that span that time period. The problem with this argument, of course, is that up until this this year, we didn't have the Manot Cave fossil, either. Perhaps, the more persuasive argument is that the Skhul/Qafzeh fossils are quite a bit more archaic than Manot Cave 1 and are morphologically closer to late archaic Homo sapiens in the shape plot they provide (this mirrors my own research in this area). On the other hand, a lot can happen in fifty thousand years and the required evolution could certainly have taken place. 
That scenario is simplistic, but may explain some things that have confounded palaeoanthropologists for over fifty years.
Another comment on this comes from geneticist and palaeoanthropologist John Hawkes who uses this story to draw attention to how the hominin population in the Levant which we've traditionally called Neanderthal have many differences between those in Europe:
There are some interesting history of anthropology observations to make about this paper and the reception to it. Most anthropologists now accept that early Upper Paleolithic European specimens, like the Oase and MladeĨ samples, have features that reflect ancestry from Neandertals. As recently as five years ago, many anthropologists still rejected that such similarities necessarily reflect Neandertal ancestry, now this seems to be utterly uncontroversial.  
It’s time to start moving the goalposts. An honest appraisal of the morphology of “Neandertals” of Israel and Syria, who lived between 80,000 and 50,000 years ago or so, shows that they differ in many ways from the Neandertals of Europe. Until now, the contrasts have been focused on the differences between these skeletal materials and the supposedly “modern” skeletal remains from Skhul and Qafzeh caves, which are somewhat earlier, between 120,000 and 90,000 years ago. But as we have found for early modern human remains in Africa, the early modern sample from Levant has a large representation of features otherwise found in archaic humans. And the Neandertals of the Levant have a large representation of non-Neandertal features. Formulating this population history as an alternation of two binary populations was always too simplistic. The real story must have been more complex. (Emphasis mine)
That is surely the take-home message: the details of human evolution as historical path are not neat and tidy, but complicated and messy. None of this however remotely means that human-ape common ancestry is false, or that humans did not originate in Africa, or that humans emerged a mere 6000 years ago. Any special creationist who attempts to use this data to make any of these crank assertions is merely betraying both a fundamentalist agenda, and a considerable ignorance of the facts.