Evolution of the human brain

[ChrisV]

I've been reading a book recently ("Our Kind", Marvin Harris) and it discussed hypotheses of the evolution of the human brain, in particular the large increase in size observed in erectus. The book advanced the theory that the increase in size was to provide backup neurons for when neurons were failing due to heat stress and exhaustion. While humans are not fast runners, we are able to run continuously for longer than virtually all species. This enables fit people to "run down" game such as deer, simply chasing them until they collapse from exhaustion. This method of hunting is still practiced by some peoples today, and could have been a selective pressure in human evolution. The book advances the idea that increasing the number of neurons in the brain enabled humans to handle heat exhaustion.

Has anyone heard this hypothesis before, and is it still thought plausible today? The book was published in 1989 so it is likely to be out of date.

[pokerbobo]

Never really looked into that...but brain "evolution" is somewhat connected to this linky on the bi cameral mind

http://en.wikipedia.org/wiki/Bicameral_mind

[Phil153]

A higher IQ is protective against head injuries and brain stress, presumably due to more neurons or more efficient/redundant wiring, so there may be some correlation.

It doesn't explain the development of these extra neurons though. The theory explains only one possible selection pressure. It's really easy to get these confused.

[born2ramble]

Sorry for the sidetrack, but:

More protective against brain stress as in:
a) deals with brain stress more efficiently and can handle larger amounts of brain stress
or
b) evades situations that lead to brain stress more efficiently

b seems unlikely. I feel like the high IQ's I know are more prone to get themselves into stressful situations -> work their way through. Just curious.

[Rduke55]

It's a pretty silly hypothesis on several levels. Developmental, logistics of wiring up, metabolic demand, etc. etc. etc. I listed some hurdles to bigger brains
here (http://forumserver.twoplustwo.com/showthreaded.php?Cat=0&Number=10438771&page=0&vc=1 )

That said, we are pretty sweet at running down prey but that's not really a brain thing.

Also, it's easy for people to get confused on some points. It's perfectly reasonable for bipedalism and other traits to ease some of the thermal restrictions on brain size, but the idea that the brain evolved to be larger to combat heat stress is really shaky.