Original URL: http://www.theregister.co.uk/2012/05/07/intelligence_and_bad_gene_copies/

Intelligence a genetic mistake

Badly copied genome boosted brains, kinda

By Richard Chirgwin

Posted in Science, 7th May 2012 23:30 GMT

It’s not quite the “key to intelligence”, but a study published in the journal Cell at least offers a hint to how human brains changed post-hominid: a miscopied gene that seems to let the brain form more connections, faster.

The paper finds that a gene dubbed SRGAP2 has, during cell divisions, been incompletely copied three times in human evolution: once around 3.4 million years ago, and again 2.4 and 1 million years ago.

The gene in question is associated with cortical development. As noted in Christian Science Monitor, duplications are an important evolutionary mechanism, acting as a kind of “sandbox” in which mutations can occur without harming an organism.

In this case, the scientists have a parallel study on which they’ve based the gene duplication / brain hypothesis. Testing one of the partial duplications, SRGAP2C, in mice, they have found two interesting developments.

The first effect they observed is that during development, the brain cells of the SRGAP2C-treated mice migrate more readily, which might provide better organization. The second effect is that the mouse brain cells showed “the emergence of human-specific features” – including the development of “spines” on the cells, which provide connection to other cells.

In other words, while the research hasn’t demonstrated that the duplicated gene leads to smarter mice (or, necessarily, to smarter humans), the studies do associate the genes with some of the things that make the modern human brain work better than Australopithecus.

The researchers also find the timing of the mutation suggestive (although not conclusive): one of the partially-copied genes seems to arrive in the human genome at around the same time as modern humans began to supplant their hominid predecessors. ®