Biology 101?
Isbell thinks proto-primates — the early mammals that eventually evolved into primates — were in a better position compared to other mammals to evolve specialized vision and enlarged brains because of the foods they ate.
“They were eating foods high in sugar, and glucose is required for metabolizing energy,” Isbell said. “Vision is a part of the brain, and messing with the brain takes a lot of energy, so you’re going to need a diet that allows you to do that.”
Modern primates are among the most frugivorous, or “fruit-loving,” of all mammals, and this trend might have started with the proto-primates.
“Today there are primates that focus on leaves and things like that, but the earliest primates may have had a generalized diet that included fruits, nectar, flowers and insects,” she said.
Thus, early primates not only had a good incentive for developing better vision, they might have already been eating the high-energy foods needed to do so.
What I want to know is, what in the hell does messing with the brain takes a lot of energy mean? I mean, that doesn’t sound, exactly, scientifically sound. It’s not like primitive primates were sitting around in mounds of fruit, straining to expand their minds – they didn’t start doing that until the 70’s. Evolution happens at birth, and as far as I know it takes no less or more energy to mutate one bit of DNA as another.
(note: if this shows up three times, it’s because LJ by email is shady right now – let me know, and I’ll remove the other two.)
While actually changing the brain probably, as you suggest, happens at birth and requires no more energy than changing your fingers, I think they probably meant that with better vision came an increase in brain activity. And that brain activity requires more energy to maintain – thusly primates who enjoyed more high-energy foods like fruit were able to maintain higher levels of brain activity for longer periods, were able to use their better sight longer, and avoid more danger leading to the eventual evolution of us.
Or something. That was coherent in my brain anyways.
I agree… and sounded coherent to me :)
My general physiology is rusty, but I recall that the brain uses glucose almost exclusively as an energy source, unlike other body tissues (which also metabolize fat and proteins). So high-sugar and high-starch foodstuffs would provide large quantities of glucose more readily than others. However, given the energy that the body would use up in converting all that glucose to protein and fats and other storage mechanisms, high-sugar and high-starch foods are not all they’re cracked up to be.
Besides, primates have always eaten meat. Not necessarily a significant (i.e. greater than 10%) portion of the diet, but look at all the big primates out there right now. Chimpanzees and gorillas will hunt, kill and eat small game (often smaller monkeys), and smaller monkeys greatly enjoy quantities of insects and eggs, although most of their diets are plant materials. Primates have always been omnivores, so saying that a high-sugar diet enabled the proto-sapiens brain evolution is not looking at the whole picture. (That, and we don’t actually have any solid dietary information for proto-primates, it’s all inferred from modern primates.)
Now as for ‘messing with the brain‘, Prof’s got it pretty much spot on.
I need a powerbar.
who is Isbell?
and also, I would point directly to other animals who eat high-energy diets but still have ‘less evolved’ vision and brains.
however, I’d need to read more about it.
In an undergraduate evolution class, we had to read a whole slew of articles on vision and eyesight and what I remember walking away from that eyesight evolution episode with was the understanding that evolution is very much a right time, right place sort of thing. and for, say, a crustacean to have vision comparable to ours (this is something to do with the rod vs. cone eye whatevers, right?), they would need eyes the size of baseball’s.
anyway, Someone else said (and I agree) that the diets of proto-primates is merely speculative.
finally, evolution isn’t even close to my area of expertise. especially animal evolution (grooosssss). Plants…now, *they* rock at evolution in totally gnarlier ways than animals did, duude.
Mendel would be proud.