Our brains got bigger because of starvation

[Laza]

I'm reading a book about human evolution ( Last Ape Standing by Chip Walter ) and i just read something interesting :

"While a chimps brain is about 350 cc, these grassland primates™ brains ran from 450 cc to 500 cc, a 25 to 40 percent increase.
The big question is why. The traditional scientific answer to this question is that a bigger brain is a better brain, so evolutions forces tended to favor smarter animals. That is true enough, but it still doesnt explain the mechanism that was causing the growth. What was forcing the issue? Why were larger brains evolving at all? Strange as it may seem, starvation might be the answer.
Numerous studies show that reducing the normal diets of creatures as different as fruit flies, mice, rats, and dogs by 35 to 40 percent will increase life span as much as 30 percent.

Cell growth on every level slows except for one key and remarkable exception: brain cell growth increases.

There the cells last longer, and they begin to make new versions of themselves faster, or at least the neurotrophins generated by the hypothalamus, which are the precursors of new brain cells, do. Not only that, other experiments show that food deprivation increases an appetiteâ stimulating peptide called ghrelin, which enables synapses to transform themselves by some molecular magic into cortical neurons.
You could say the body and the brain strike a bargain. To compensate for the aggressive growth of new neurons, the rest of the anatomy fasts, stretching scarce nutritional resources that it then redirects to the brain. "

I never heard of this before, what do you think ?

[Chad32]

So we got smarter, and thus got the one edge we have over practically everything else in the world (outside of running endurance), because at one time we weren't doing very well as a species?

[Anomalocaris]

What you are describing is an acquired trait - An response of the organism to a condition. Acquired traits are not heritable. The trait must have a genetic basis to be heritable. So if what you are saying about brain growing in response to starvation is true, it would only explain why the starving individual's brain might be larger, it can't explain why the brains of his non-starving offsprings also got bigger.

[dornzzz]

australopithecenes weren't chimps... why then would their brains need to be exact size?

whilst australopithecenes were apes as much as chimps bar walking on all fours, it's possible they needed a bigger brain due to different behaviour. gorillas and chimps are both apes, but aren't the same behaviourally.

[max-greece]

What you are describing is an acquired trait - An response of the organism to a condition. Acquired traits are not heritable. The trait must have a genetic basis to be heritable. So if what you are saying about brain growing in response to starvation is true, it would only explain why the starving individual's brain might be larger, it can't explain why the brains of his non-starving offsprings also got bigger.

Unless there is a heritable trait in there somewhere - like a greater capacity to increase brain size in response to certain conditions.

Its the first time I have heard of this theory so I can't say I have an opinion on it. There maybe something there but this doesn't look like the only answer.

Maybe in conjunction with the pressure put on the species by the change of habitat which rewarded these bipedal, slow moving, poorly armed hominids which could adapt the best - as in think their way out of the problem.

Further, it would explain the 40-50% of Americans who overeat and believe in creation. The more burgers you eat, the dumber you get.

[KUSA]

People in Ethiopia must be some smart mutherfuckers from all that lack of food.

[Wyrd of Gawd]

Humans have the slowest metabolism of all of the primates, which contributes to our long lifespans. So maybe the slow metabolism and long lifespans enables us to have larger brains.

BTW, since our brains use about 20% of our daily calories it seems that starvation is not the way to get a larger brain.

[Clueless Morgan]

BTW, since our brains use about 20% of our daily calories it seems that starvation is not the way to get a larger brain.

Exactly what I was thinking: why would the body's reaction to lack of food be to increase the size of an organ that's one of, if not the highest energy consumers in our bodies?

[Anomalocaris]

If the marginal benefit conferred by a bigger brain in acquiring calories is greater than the marginal calorie requirements of the bigger brain, than bigger brain, despite its calory requirement, would be of survival benefit in times of scarce calorie supply.

Btw, humans have well below average overall rate of metabolism compared to other large mammals of comparable body size and mass. So it seems reasonable to suppose some time on our primate evolution path, there was great selective pressure to reduce calorie intakes - ie cutting down on calorie intake conferred greater benefit than any profitable use we could put additional calories to. So that seem to run against the theory of survival benefit of bigger brains outweigh its calorie demand.

[vorlon13]

I guarantee the effect does not work on our dieting cat. Little Tubby there has definitely experienced a 50% drop in smarts since he went from 27 pounds to 18.

Bad Kitty!! Bad!! Bad!! Kitty !!!