Friday, March 15, 2013

Eyes Versus Brain

This is interesting - there is a new theory that the reason Neanderthals went extinct is because they had larger eyes and better vision for the long, dark days of northern Europe. Because more of their brain was devoted to processing vision, it constrained the development of brain structures such as the neocortex for larger social networks, language and intelligence that arose in homo sapiens. This led to their being outcompeted, the thinking goes.
The research team explored the idea that the ancestor of Neanderthals left Africa and had to adapt to the longer, darker nights and murkier days of Europe. The result was that Neanderthals evolved larger eyes and a much larger visual processing area at the backs of their brains. The humans that stayed in Africa, on the other hand, continued to enjoy bright and beautiful days and so had no need for such an adaption. Instead, these people, our ancestors, evolved their frontal lobes, associated with higher-level thinking, before they spread across the globe.

Ms Pearce found that Neanderthals had significantly larger eye sockets - by an average of 6mm from top to bottom. Although this seems like a small amount, she said that it was enough for Neanderthals to use significantly more of their brains to process visual information.

"We infer that Neanderthals had a smaller cognitive part of the brain and this would have limited them, including their ability to form larger groups. If you live in a larger group, you need a larger brain in order to process all those extra relationships," he explained. The Neanderthals' more visually-focused brain structure might also have affected their ability to innovate and to adapt to the ice age that was thought to have contributed to their demise.
Neanderthals' large eyes 'caused their demise' (BBC)

The research was overseen by Scottish psychologist Robin Dunbar, famous for Dunbar's number - a relation of the size of the neocortex and brain volume to the size of a species' natural social group. His research found that people have a basic social group size of 90 to 220 individuals, bracketing the number 148 which is what the ratio would indicate for anatomically modern humans. He also hypothesized that language, and more specifically gossip, evolved to substitute for primate grooming in creating group cohesion, beacuse grooming 148 individual people would take all day.

The role of energy tradeoffs in explaining evolutionary questions seems to really gaining steam. It's similar to the hypothesis that using fire to cook allowed our jaws and intestinal tracts to shrink, freeing up metabolic energy for rapid brain growth. This energy approach seems like a promising avenue for investigation.

Here is more: Neanderthals Lacked Social Skills (Discover) and From Neanderthal Skull to Neanderthal Brain? (National Geographic)

And this particularly appeals to me as an architect: Neanderthals build dwellings out of mammoth tusks. Awesome. Me done blogging. Me go bed now.


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