There is no doubt that today we know by virtue of fossils and genetics that Human species evolved in Africa and gradually moved out eventually conquering the world. Fossils have also indicated that multiple species of humans roamed across the world until recently.
It is a general consensus that Neanderthals existed in Europe 400,000 years ago, reached western Asia 150,000 years ago then went extinct 30,000 years ago. How far did the Neanderthals conquered? Did the Neanderthals really go extinct? What caused their extinction—was it the Ice Age brought by Toba volcano some 75,000 years ago? Or was it the fury of this newer more intelligent species, the Homo sapiens (Humans) that doomed the older bipedal ancestors? Or was it interbreeding of the two hominid species that united them to weather the Ice Age?
What caused extinction of Neanderthals?
There is a consensus that eruption of super volcano Toba (Indonesia) and the Ice Age that followed has impacted human evolution like no other events. The numbers of Homo sapiens dwindled down to less than 10,000 and no other hominid fossil have been found post-Toba eruption. Although it is currently believed that Neanderthals went extinct because they could not compete with Humans for food, an argument can be made that they might have been integrated with modern humans for survival.
Even though the lack of fossils post-Toba eruption indicates that the only humans to exist were Homo sapiens, there has not been any conclusive evidence demonstrating that the remaining Homo sapiens directly or indirectly forced the remaining Neanderthals to extinction. While Neanderthals were archaic compared to Homo sapiens, they had developed language and culture. Thus it may be safe to assume that they interacted well with Homo sapiens. It seems logical to believe that two similar species, both possessing cultural values and ability to speak languages might have come together at time of dire straits to ensure survival. In the course of survival, they might have interbred with each other and if that was indeed the case, then Neanderthals might not have gone extinct. They might be within us, in our genome.
What leads me to believe that Humans and Neanderthals interbred?
There were two major papers recently published—first by Noonan et al in Science and another by Green et al in Nature. Both papers were about analyzing the Neanderthal DNA and a third paper by Wall et al was published in PLoS Genetics, which cautioned readers about the validity of the previous two papers. Wall found “possible contamination” of human DNA in sequences offered by both the papers. What Wall believes as contamination could be the result of human inbreeding with the Neanderthals.This idea of humans and Neanderthals inbreeding might seem bizarre but there is nothing that argues against it. May be one day some genetic study would convincingly prove that humans and Neanderthals did not breed but until then there is always a chance that Neanderthals prevailed by transferring their genes to us.
How far did the Neanderthals reach?
Although newer findings are revealing more about the Neanderthals, there is yet another question to be answered—how far did the Neanderthals reach? Johannes Krause suggested in journal Nature that Neanderthals had reached “Uzbekistan and in the Altai region of southern Siberia.” With discoveries of newer fossils we are discovering that Neanderthals had reached much farther than we initially thought. Interestingly, no one has looked south of Hindu Kush for Neanderthal fossils. A presumably Ramapithecus mandible was found in Nepal. Ramapithecus was much older than Neanderthals. May be the Neanderthals reached the Foothills of the Himalayas too?
In addition to lack of interest, the lack of search for Neanderthals in the Indian Subcontinent might have been discouraged because not many fossils have been found in that area. But I have always wondered if the eruption of super volcano Toba has anything to do with it. May be the Neanderthals existed in the Indian Subcontinent and got buried below the ashes of Toba. May be if we dig deeper in the soils of the Himalayas we can discover that Neanderthals roamed there before their fate was sealed by Toba. I am not an archeologist so my suggestions to look for Neanderthals in the Indian Subcontinent may sound bizzare to some.
But these question still remain unanswered: how far did the Neanderthals reach and did they really go extinct or did they simply passed their genes on to us? Hopefully genetics and archeology can answer these questions in near future.