[Originally posted Nov. 8, 2010]
Why did the European Neanderthals, the last of their kind, disappear at the same time as anatomically modern humans colonized Europe? Indications are that they somehow could not cope with the competition but why, exactly, were the moderns able to outcompete the Neanderthals? No one has been able to show that they were less intelligent and their brain size was at least equal to our own. It isn’t plausible that they would have a large brain without using it to the fullest. The claim that we only use a small part of our brain is a modern myth; on the contrary “…all animals are under stringent selection pressure to be as stupid as they can get away with” (Richerson & Boyd, Not by Genes Alone, 2005, p. 135).
The Neanderthals were certainly stronger and more robust than most of us moderns but this is not necessarily an evolutionary advantage; it also means that they required more sustenance (Kate Wong, “The Mysterious Downfall of the Neanderthals”). Each of them had to eat more than each of us so that a band of Neanderthals living in a similar environment and with a similar survival strategy would either have been smaller or required a larger territory than a band of anatomical moderns. Their population densities must have been lower. Additionally, they may have eaten more meat (been higher up the food chain) than the Cro-Magnon moderns that replaced them, which has the same effect (although this may be a sign of their lesser adaptability – below).
Their smaller numbers may have been a handicap if they had to confront Cro-Magnons in physical conflict and the number of spear-throwers was more important than their physical strength.
More important, however, is probably the smaller size of their communities, which results in a simpler and less adaptable culture. Humans are fairly unique in the animal world in the fact that their extraordinarily complex culture makes them adaptable far beyond any other animal and a complex and rich culture is normally more adaptable than a simple one.
Just like a large brain with many brain cells has more cognitive power than a small brain, a large community stores more knowledge and can explore more ways to adapt than a small community can. The Tasmanians, after they got isolated from their Australian mainland cousins, considerably simplified their material culture (Richerson & Boyd, p. 138).
Their richer and more adaptable culture would have given the Cro-Magnons an advantage over the Neanderthals with the result that they gradually got the upper hand in competition, especially when the climate became volatile, requiring faster adaptation (cf. Richerson & Boyd, p. 136). This advantage of the anatomically moderns need not have been great to gradually give them the upper hand. After all, it took the Neanderthals some 15,000 years to disappear after the coming of the moderns. It was only around 30,000 years ago, significantly at a time of unstable climate, that they finally vanished.
Anatomical moderns did not outcompete Neanderthals because they were smarter or more adaptable one by one. It was only because their groups were larger and therefore more adaptable (for group selection see D.S. Wilson, Evolution for Everyone, 2007). According to this scenario, their respective cultures of the Cro-Magnons and the Neanderthals were influenced by genetically determined phenotypes; nevertheless, it was cultural competition that determined the survival of one and the demise of the other.