The short story on the back page of this weeks Nature (vol.453, p.562) has an interesting premise: that the Neanderthals developed the "nerdy" genes which in moderate doses make you good at maths and physics, while more extreme cases end up with autism. Easy to imagine that it's the lack of social cohesion that sealed their demise when they were competing against the more politically minded (and probably aggressive) Cro Magnon. The story suggests that the presence of autism genes in our population, which largely descends from Cro Magnon humans, is due to the (debated) interbreeding with Neanderthals.
The author, New Scientist correspondent Jeff Hecht, got one detail wrong -- the autism-related genes aren't dying out, as he suggests at the end of the story (which is set in a not-too distant future). On the contrary, the technological revolutions of the last two centuries, with the huge growth in demand for maths/phys/engineering type people, has ensured that the genes have spread and autism is much more common than it used to be when it was first described.