Three gene 'flaws' made our brains grow

Seven bil­lion brain cells mark your brain from that of a go­rilla, thanks to three genes that have changed since evo­lu­tion sep­a­rated hu­mans and apes.

Science Illustrated - - SCIENCE UPDATE -

In 14 mil­lion years, the hu­man brain has grown from about 0.5 kg in our ear­li­est an­ces­tors to 1.4 kg, prob­a­bly thanks to three newly-iden­ti­fied genes.

Cal­i­for­nian sci­en­tists spot­ted the genes, when they stud­ied how many nerve cells a macaque pro­duces in its brain. They cul­ti­vated the an­i­mals’ brain tis­sue in the lab, par­tic­u­larly fo­cus­ing on NOTCH genes, which in­flu­ence the de­vel­op­ment of stem cells in em­bryos. The sci­en­tists dis­cov­ered that hu­mans have three ac­tive NOTCH genes on chro­mo­some 1, which do not ex­ist in macaques nor in our clos­est rel­a­tives, chimps and go­ril­las, i.e. the three genes are unique for hu­mans. So, sci­en­tists can re­con­struct our evo­lu­tion­ary his­tory.

The first gene emerged as a par­tial copy of a gene on chro­mo­some 1 some 14 mil­lion years ago, be­fore hu­mans parted from the other apes. 11 mil­lion years later, the gene was re­paired, coin­cid­ing with the time when the hu­man brain started to grow. Later, the gene was copied two more times. Other sci­en­tists have re­vealed that the three genes code for a pro­tein that causes the stem cells of the brain to di­vide in four in­stead of two nerve cells. The re­sult is that we pro­duce many more nerve cells than other pri­mates.

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