The birth of a gene that fueled neurotransmission may have been a key advance in the evolution of the hominoid brain, according to a study in the October issue of Nature Genetics. The study reveals that a human and ape brain gene involved in glutamate metabolism was retrotransposed from a widely expressed housekeeping gene in the beginning of the hominoid lineage.

Henrik Kaessmann and Fabien Burki of the University of Lausanne, Switzerland, detected the gene, GLUD2, in humans and apes, but not in Old World monkeys, indicating that the gene appeared after monkeys and hominoids went their separate ways—about 23 million years ago—but before the gibbon lineage split from humans and great apes around 18 million years ago.

After the retrotransposition, the new glutamate metabolism enzyme, called GLUD2, went through several million years of positive Darwinian selection, say the authors. By combining these new genetic data with previous...

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