Why are primates big-brained?"brain size is predicted by diet rather than by the various measures of sociality"

[SteveG]

Great Moments in Primate Evolution- ordering out for lunch

It's not who you know, it's how you gather dinner...
Read more at: https://phys.org/news/2017-03-primates-b...t.html#jCp
Brain size in primates is predicted by diet, an analysis by a team of New York University anthropologists indicates. These results call into question "the social brain hypothesis," which has posited that humans and other primates are big-brained due to factors pertaining to sociality.

The findings, which appear in the journal Nature Ecology and Evolution, reinforce the notion that both human and non-human primate brain evolution may be driven by differences in feeding rather than in socialization.
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Their results showed that brain size is predicted by diet rather than by the various measures of sociality—after controlling for body size and phylogeny. Notably, frugivores and frugivore/folivores exhibit significantly larger brains than folivores and, to a lesser extent, omnivores show significantly larger brains than folivores.

The researchers caution that the results do not reveal an association between brain size and fruit or protein consumption on a within-species level; rather, they note, they are evidence of the cognitive demands required by different species to obtain certain foods.

"Fruit is patchier in space and time in the environment, and the consumption of it often involves extraction from difficult-to-reach-places or protective skins," observes DeCasien."Together, these factors may lead to the need for relatively greater cognitive complexity and flexibility in frugivorous species."




"We believe not ordering off the kids menu changed everything."

[pdq]

I saw an alternate theory discussed on PBS a couple years ago. An MS researcher had found a mutation resembling MS in the temporalis (and masseter?) muscles in more or less all humans. Apes are known to have incredible bites, and these muscles are responsible for them. But in order to work, they need solid jaw and head bone to hold on to, and human babies skulls aren't fused and complete for much, much longer than gorillas or chimpanzees.

Bottom line: in order to bear the forces this bite produces, apes skull bones fuse and form a solid backing for these bite muscles early, which has the side effect of limiting brain size. Human cranial bones are incomplete much longer (open "fontanelles") allowing the brain (and skull) to grow before and after birth at the cost of reduced bite strength.

[Wags]

I believe that the key breakthrough for hominids was the mastery of fire and cooking. Cooking food makes a lot more calories available from any given source, basically outsourcing a significant part of digestion.

[davester]

As noted, there are several competing hypotheses for hominid brain evolution, one, some or none of which may be correct.

[cbelt3]

No monolith?

[AllGold]

pdq wrote:
I saw an alternate theory discussed on PBS a couple years ago. An MS researcher had found a mutation resembling MS in the temporalis (and masseter?) muscles in more or less all humans. Apes are known to have incredible bites, and these muscles are responsible for them. But in order to work, they need solid jaw and head bone to hold on to, and human babies skulls aren't fused and complete for much, much longer than gorillas or chimpanzees.

Bottom line: in order to bear the forces this bite produces, apes skull bones fuse and form a solid backing for these bite muscles early, which has the side effect of limiting brain size. Human cranial bones are incomplete much longer (open "fontanelles") allowing the brain (and skull) to grow before and after birth at the cost of reduced bite strength.

There are also structural differences between human and ape skulls that don't support the higher bite strength in humans, even in adults.