Concerning the question of why the relative brain sizes of smaller organisms are larger:
Doesn't it seem obvious that this is due to the entirely different nature of the nervous system and its function compared to other tissues? For example, a salivary gland will work the same whether it has 10,000 or 20,000 cells, appropriate to two species of fruit flies, one twice the size of the other. But given that neurons have a lower limit in size (as the article points out), one cannot halve the number of neurons and achieve the same behavioral complexity. And a fly half the size needs roughly the same behavioral reportoire, since it must react to threats, find food and mates, etc. pretty much the same.
posted by Bruce Blackwell
May 21, 2012
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