By David Coppedge

Credit: © Valeriy Kirsanov / Fotolia

Brain size can’t be used as an independent measure of fitness, five evolutionary anthropologists contend.

How long have evolutionists told us that our relative brain size gave us the fitness edge as we evolved from apes?  That assumption has been called into question by Jeroen B. Smaers and four European colleagues in a new paper in PNAS (Smaers et al., “Comparative analyses of evolutionary rates reveal different pathways to encephalization in bats, carnivorans, and primates,” PNAS October 15, 2012, doi: 10.1073/pnas.1212181109).

First, Smaers & friends pointed out the long history of the assumption.  A summary of the paper on Science Daily says,

Dr Jeroen Smaers (UCL Anthropology and UCL Genetics, Evolution & Environment), lead author of the study said: “When using brain size relative to body size as a measure of intelligence, the assumption has always been that this measure is primarily driven by changes in brain size.  It now appears that the relationship between changes in brain and body size in animals is more complex than has long been assumed.

“Changes in body size often occur independently of changes in brain size and vice versa. Moreover, the nature of these independent changes in brain and body size, are different in different groups of animals.”…

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