martes, 23 de octubre de 2012

Invention of cooking made having a bigger brain an asset for humans

Raw diet makes feeding 86bn neurons a nine-hour-a-day job, which explains evolutionary tradeoff in gorillas, scientists find

If human beings had not invented cooking as a way of increasing the number of calories they consumed, they could only have supported the 86bn neurons in their big brains by spending an impossible nine hours or more each day eating raw food, according to a scientific paper published on Monday.

The research, the authors suggest, explains why great apes such as gorillas, which can have bodies three times the size of humans, have considerably smaller brains. Though gorillas typically spend up to eight hours feeding, their diet influenced an evolutionary tradeoff between body and brain size; supporting both big bodies and big brains would be impossible on a raw food diet.

The brain is so energy-hungry that in humans it represents 20% of the resting metabolic rate, even though it only represents 2% of body mass, suggest Professor Suzana Herculano-Houzel and Karina Fonseca-Azevedo of the Institute of Biomedical Sciences at the Federal University of Rio de Janeiro.

"Why are the largest primates not those endowed with the largest brains as well? Rather than evidence that humans are an exception among primates, we consider this disparity to be a clue that, in primate evolution, developing a very large body and a very large brain have been mutually excluding strategies, probably because of metabolic reasons." [...] guardian.co.uk/

Reference: Karina Fonseca-Azevedo andSuzana Herculano-Houzel.
Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution .
PNAS 2012 ; published ahead of print October 22, 2012, doi:10.1073/pnas.1206390109

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