IT IS nothing short of an identity crisis: for all these years we have wrongly believed that human brains were uniquely well endowed in the areas that produce higher thought and reasoning.
Now researchers have found that it is simply not so. Our large frontal cortex is simply a result of having a larger brain. In fact, it turns out lemurs have more frontal cortex relative to their brain size than we do.
Many people, including the great 19th-century neuroanatomist Korbinian Brodmann, believed that primates’ frontal lobes got progressively bigger relative to the rest of the brain as you moved from primitive prosimians through to humans. But although some people have challenged this view, it has never been properly tested.
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Eliot Bush and John Allman at the California Institute of Technology in Pasadena decided to put the matter to rest by examining the brains of 55 mammalian species, including 25 primates, across eight orders.
The researchers found that in primates, the frontal cortex simply grows relative to the rest of the cortex: it does not, they say, get disproportionately bigger along the evolutionary line leading to humans (Proceedings of the National Academy of Sciences, vol 101, p 3962).
“Nobody is special,” says Bush. “It’s just something about primates.”
