Human OriginsAre we hybrids?BY EUGENE M. MCCARTHY, PHD GENETICS
— This article is a bit different from others that have appeared on this site, in that it's about some of the findings of my own research. I'm a geneticist whose work focuses on hybrids and, particularly, the role of hybridization in the evolutionary process. Here, I report certain facts, which seem to me to indicate that human origins can be traced to hybridization, specifically to hybridization involving the chimpanzee (but not the kind of hybridization you might suppose!). You can access detailed and documented discussions supporting this claim from links on this page. But the basic reasoning is summarized here, without a lot of citations and footnotes.Rationale
So why do I think humans are hybrids? Well, first of all, I've had a different experience from most other people. I've spent most of my life (the last thirty years) studying hybrids, particularly avian and mammalian hybrids. I've read thousands, really tens of thousands, of reports describing them. And this experience has dispelled some mistaken ideas I once had about hybrids, notions that I notice many other people continue to take for granted.
For example, one widespread, but erroneous belief that keeps a lot of people from even considering the possibility that humans might be of hybrid origin is the notion that all hybrids are sterile. This assertion, though I've heard lots of people say it, is absolutely false. For instance, in reviewing the reports I collected for my book on hybridization in birds (Handbook of Avian Hybrids of the World, Oxford University Press, 2006), which documents some 5,000 different kinds of hybrid crosses among birds, I found that those producing partially fertile hybrids are about eight times as common as crosses known to produce sterile ones. So the usual result is a reduction in fertility, not absolute sterility. My current work documenting hybridization among mammals shows that partially fertile natural hybrids are common, too, in Class Mammalia. And yet, it seems most people base their ideas of hybrids on the common mule (horse x ass), which is an exceptionally sterile hybrid, and not at all representative of hybrids as a whole.
A second "fact" that might make it seem impossible for humans to have had a hybrid origin is the equally erroneous notion that hybrids, especially successful hybrids, do not occur in a state of nature. A third is the mistaken idea that only plants hybridize and never animals. In fact, however, natural, viable, fertile animal hybrids are abundant. A wide variety of such hybrids occur on an ongoing basis (read a detailed discussion documenting these facts). For example, of the 5,000 different types of hybrid crosses listed in my book on hybridization in birds, approximately half are known to occur in a natural setting (download a PowerPoint presentation summarizing data on hybridization in birds). My current research indicates a comparable rate for mammals.
more at: http://www.macroevolution.net/human-origins.html#.Uddxem1p73t