That's not all. Yesterday Dienekes wrote :
Although I agree that the end of the Ice Age was a necessary factor for the development of agriculture in Eurasia, it is too simplistic to say that it was the only reason. As he said himself, "humans" had been hunter-gatherers for millions of years. There were plenty of climatic variations during that period. Obviously the anatomically modern humans only appeared 200,000 years ago. But that is still plenty of time to develop agriculture. The Ice Age is a poor excuse for not developing agriculture since most of humanity lived in Africa or South Asia, where it was warm enough to farm. Furthermore, the Neolithic revolution wasn't just about farming, but also about making pottery and domesticating animals. Why didn't humans in Africa think about that earlier ?Originally Posted by Dienekes
What really changed is our brains, from about 50,000 years ago, when Homo Sapiens left Africa and started mingling with Neanderthals in the Middle East, then again in Europe and Central Asia 30 to 40,000 years ago. This was a crucial part of our recent evolution. Two sexually compatible types of hominids would meet for the first time (?) since they split from each others at least 700,000 years ago. The combined immune systems made the hybrid children stronger (as attested by a study this year). And the hybrid offspring could have inherited the best characteristics of each subspecies, including the best alleles for intelligence, adaptability, imagination, heat and cold resistance, social skills, and so on. Some of the hybrid offspring got many bad alleles from each parent and were eliminated from the gene pool through natural selection. This was a long process, probably spanning on tens of thousands of years. I believe that this is the reason why cave paintings suddenly appeared out of nowhere around 32,000 years ago in Europe, just a few thousands years before pure Neanderthals disappeared completely. Pure Homo Sapiens and pure Neanderthals each had their own qualities, making it impossible for one to eradicate the other for 30,000 years since they first met. But neither could compete with the new hybrids.
Consequently, when the climate eventually got warmer, the Eurasian survivors had inherited the most beneficial genes from both Homo Sapiens and Neanderthal, and were more creative and adaptable than any human had ever been before. This is why agriculture and pottery were invented (and could be invented at all) in such distant places as the Middle East and China/Japan roughly around the same time, then independently again a bit later by other Neanderthal hybrids in Papua and the Americas.
Agriculture only reached sub-Saharan Africa when a back migration of the new Middle Eastern hybrids "updated" the gene pool (they were surely the E1b1b, T and R1b-V88 lineages which are dispersed all around Africa today).
Australian Aborigines never developed farming, pottery, etc. because they descended from the first migration of Homo Sapiens out of Africa, the one that departed from East Africa 70,000 years ago and followed the coast of South Asia until Australia. Therefore they never interbred with Neanderthals (although they seem to have mated with the archaic Southeast Asian Homo Erectus, descended from the Java Man), and apart from a few very localised contacts with Papuans or South Asians never really had a fresh influx of new genes from outside either (unlike sub-Saharan Africans) before the Europeans arrived.
Dienekes rejected the idea of interbreeding with Neanderthals, so he obviously couldn't have thought about it. As usual he took the chose the first easy solution that any child could have thought of.