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Genetic tweaks built humans’ bigger brains

Experiments in mice show how to grow a wrinkled cortex

2:00pm, February 26, 2015
Big Brain

FOLD IT  A gene that only humans have can make the normally smooth outer layer of mouse brains develop folds similar to those in human brains (upper right center). The gene may have been important for the evolution of big human brains.

Human brains ballooned to about triple the size of their ancestors’ thanks to just a few genetic tweaks, new research suggests.

When scientists inject a gene found only in humans into the brains of mouse embryos, the normally smooth mouse brain develops the crinkles and folds reminiscent of wrinkly human brains, scientists report online February 26 in Science. The wrinkles are a sign that the brain’s outer layer, or cortex, is growing. 

That discovery closely follows a report from Duke University researchers who have found a genetic switch that boosts brain size. The human version of that switch produces a 12 percent larger cortex than a chimpanzee version does, the Duke team reports February 19 in Current Biology.

Together, the two studies present some of the first genetic

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