Modern Genetics and Ancient Humans

Yet again, a new study seems to have found evidence of the interbreeding of ancient human populations.


The details are much too complicated (for me at least) to get into in this post, but it now appears that there were at least four (possibly five) genetically identifiable human groups on the planet during the last couple 100 thousand years.

• Anatomically Modern Humans (AMH)--at the moment, this seems to be the major lineage that becomes what we are today.  Fossil evidence points to their emergence around 200,000 years ago in Africa.  In the last 50,000 years, this population seems to have expanded throughout much of the rest of the planet.
• Neandertals--a group of humans living in Europe and central Asia during roughly the same period.  Lots of archaeological and paleoanthropological data exists for these folks.  During the last few years, a lot more genetic evidence has also become available.  This evidence demonstrates that AMH and Neandertals interbred when they came into contact with one another in southwest Asia.
• Denisovans--Not much is known about these people archaeologically or paleoanthropologically, but a genome has been sequenced in the last couple of years and compared to living peoples. The genetic material was recovered from a few bones found in a cave in southern Siberia. Similarities between Denisovan segments of DNA and those of living Melanesians suggest interbreeding took place between the Denisovans and groups of AMH moving through Asia.  The Denisovans seem to have lived throughout much of eastern Asia.
• Archaic Africans--the study mentioned in the first sentence of this post refers to these folks.  There seems to be distinctive segments of DNA that suggest they originated from an archaic population and these distinctive segments are only found among several living groups of African peoples. 
• Homo floresiensis--last and least (stature-wise) are the strange small people of the island of Flores in Indonesia.  In many ways the jury is still out on these folks (as it is on many of the studies mentioned above as well) and no genetic material has been recovered.

To me, all of this points to the fact that evolution is messy and boundaries are never clear cut.  While some ancient populations may have developed distinctive genetic sequences and morphologies, they still did not differ enough from one another to prevent interbreeding when these groups came together.  So, while I identified AHM as the major lineage that led to humans today, humans today are also made up of bits and pieces from these other ancient groups.

Additionally, the genetic evidence shows interbreeding and really doesn't inform on cultural change at all.  The archaeological record still is essential for providing that kind of information. However, we at least now can ask questions about the the co-constructive processes of cultural changes, population movements and interbreeding.