Theories of Hominid Brain Evolution?

Question

I have heard the standard "they got more protein from hunting and therefore brains got bigger" but I was wondering if there are any other theories about why brains expanded.

Answer 1

The increase in protein would explain HOW their brains got bigger - but not WHY.  There would still have to be selective pressure driving the increase.

There are a lot of running hypotheses, but two are more prominent:

1)  Kaplan, et al:  Big brains helped us be better hunter/gatherers, so the people who were smarter were able to get better resources and were more likely to survive.

2)  Joffe/Alexander/et al:  Social competition and sexual selection.  The socially "smart" individual was much more likely to be selected as a mate than the clueless idiot.  Therefore, smart people had more babies.

I'm personally a fan of the second hypothesis, but there are no clear answers.  It's unlikely that there was ONE main driving force, anyway - evolution is complicated.

Answer 2

Right, protein and fats are high in energy and can support large brains. However, remember that large brains are favored in apes, many of which do not eat meat (including the earliest hominins). Certainly meat allowed for a large jump in brain size.

Answer 3

The " social interaction theory " is actually more coherent. Just think of all the social interactions you must keep track every day. Our ancestors, though living in small groups, had nothing else so pertinent to them as their interactions with close relatives and the tribe in general

Answer 4

My favorite theory is that certain fatty acids from eating scavenged brain material provoked hominid brain evolution.  This would have facilitated brain evolution even before hunting because carcasses usually have their skull in tact.   Hungry hominids could then break open the skull with a stone tool and extract the brain tissue.   Brain matter has even higher levels of beneficial fatty acids than seafood.  And this theory doesn't necessitate that the hominids live near the ocean.

I like this theory because it's gross and no one likes to talk about it even though it's totally feasible.

Answer 5

I read that seafood was an important factor and it makes some sense. That living by the waterside eating different from others would cause extreme changes.  Swimming and diving would cause different breathing patterns.  I think, also, that hand to eye coordination was a factor.  Yes, a social system was important but many animals are social.