Razib has rounded up a lot of the posts on the recent Neanderthal news. Kambiz has also written the first of a multipart series on the subject. MSNBC is also reporting that twom different papers will be published on the subject of Neanderthal DNA. One, by the Paabo group, will be pubished in Nature. The other, by a group headed by Rubin, will be published in Science. Apparently, over a million bases have been identified (note this is not mtDNA). That being the case, I thought I would start some background posts to try and demonstrate how this will impact our views on Neanderthals.
I don’t propose to go into a lot of the material that has already been covered. Suffice to say, people have been arguing over the place of Neandethals since the time of Virchow. This type of argumentation reached it’s peak in C. Loring Brace’s article The Fate of the “Classic” Neanderthals: A Consideration of Hominid Catastrophism published in Current Anthropology back in 1964. The issues Brace discussed back then still play a role in the current debate, but there are other issues that have arisen since that play a role. When I was in college the “must read” paper on Neandethals and the origins of modern humans was a paper by Smith, Falsetti and Donnelly – Modern Human Origins – published in the 1989 Yearbook of Physical Anthropology. The paper summarized three different models for the origins of modern humans.
The first, called the Afro-European Sapiens (AES) model was advocated by Gunter Brauer. According to the AES modern humans evolved from an early archaic Homo sapiens stage. This stage is represented by finds at Bodo:
As well as Ndutu, Eyasi and Elandsfontein.This early group gave rise to a population transitional between them and early modern Africans. The transitional group is represented by finds in Florisbad:
and Omo (specifically Omo 2):
As well as Ngaloba. According to this scenario modern humans then moved out of Africa through a gradual process due to climate and environmental change. The AES does not view this as a biological speciation event. Consequently, expanding modern populations could assimilate “archaic” genes into their gene pool.
The second model is the Recent African Evolution (RAE) model. Also called the Out of Africa model, it’s primary advocates are Stringer and Andrews. (I will have more to say about this below) The RAE model proposes that modern humans arose in Africa within the last 200, 000 years and spread around the globe, replacing other populations as they went. In this model the origin of modern humans was definately a speciation event. Advocates of RAE do not, consequently allow for any kind of assimilation of archaic genes – or at least don’t think it had a significant impact on human evolution
The third model is the Multiregional Evolution (MRE – aka mulitregional continuity) model. Argues that there is a large amount of morphological and genetic (and aruably cultural) continuity throughout Eurasia and Africa. As Smith et al put it:
This would mean that paleontological indications of continuity, particularly transitional fossils and regionally distinct morphological features linking archaic and modern humans in specific geographic regions, should be found in Eurasia as well as Africa, but not necessarily that such indications should be common…or that significant continuity characterizes every region.
For the most part the AES has been collapsed into the MRE and the debate has largely focussed on MRE vs. RAE. In the next post I will take a closer look at the RAE.