DID shrinking guts and high-energy food help us evolve enormous,
powerful brains? The latest round in the row over what's known
as the "expensive tissue hypothesis" says no. But don't expect
that to settle the debate. The hypothesis has it that in order
to grow large brains relative to body size, our ancestors had to
free up energy from elsewhere - perhaps by switching to rich
foods like nuts and meat, which provide more calories and
require less energy to break down, or possibly by learning to
cook: cooked food also requires less energy to digest. Kari
Allen and Richard Kay of Duke University in Durham, North
Carolina, turned to New World monkeys to explore the hypothesis.
Previous studies offer a wealth of data on the monkeys' diets
and show that their brain size varies greatly from species to
species. But when the pair controlled for similarities between
related species, they found no correlation between large brains
and small guts (Proceedings of the Royal Society B, DOI:
10.1098/rspb.2011.1311). As Robin