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The more literature I read about this, the more compelling I find this. In mammals, the larger the body the larger the brain. That's because you need all those neurons to control all those muscles. I recently read some papers that hypothesize the muscle atrophy we experience as we get older is partially the result of the neurons controlling those muscle-fibers dying [1]. As infants, our brains grow into our bodies by producing more neurons than we need and then killing off the neurons that aren't being used [2]. It makes sense to me that if we don't use our bodies in a variety of exercises, the lack of signal from the muscles to the brain could result in pruning those neurons as we get older.

[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3868452/

[2] http://mxplx.com/meme/922/




As a potentially related point - in autistic individuals there is markedly less synaptic pruning:

http://www.cell.com/neuron/abstract/S0896-6273(14)00651-5?_r...


Does this mean you're saying you need _bigger_ muscles specifically to get bigger brains?


Is an elephant really more intelligent than a human then?


Nautilus has an article[1] that explores exactly this question. I beleive the conclusion was that it is the number of cortical neurons, not the total number of neurons and not brain mass that best predicts intelligence, or at least best correlates with our intuitive ranking of intelligence that puts humans and then primates at the top, above elephants.

[1] - http://nautil.us/issue/35/boundaries/the-paradox-of-the-elep...


No, an elephant needs a larger brain to run its larger body. Humans have enough brains to run our bodies, plus "extra" with which to think, in a manner of speaking.

https://en.wikipedia.org/wiki/Encephalization_quotient


I've always thought the metabolic needs must have been just as driving (specifically, being carnivores). Note: not a dig at vegetarians, we're talking about long before the proliferation of tofu and quinoa.

"A gram of brain tissue takes 20 times more energy to grow and maintain than a gram of tissue from the kidney, heart, or liver"

http://news.harvard.edu/gazette/story/2008/04/eating-meat-le...


I think he's not talking about intelligence, but about muscle control which kind of makes sense..




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