Traces of the transition from fins to limbs linger in the human body, Shubin said, with implications for biomedical research.

Researchers have pinpointed a genetic mutation that may help explain why some men are less fertile than normal, a new study in the 20 July issue of the journal Science Translational Medicine reports.

The gene encodes a protein called beta-defensin 126, which coats the surface of sperm and helps them penetrate cervical mucus in women. Men with a variant of this gene, called DEFB126, lack beta-defensin 126, making it much more difficult for sperm to swim through the mucus and join with an egg.

The 91st Annual Meeting of the AAAS Pacific Division will convene 13-17 June in Ashland, Oregon, with a program featuring talks on wolves, wildlife forensics, and watersheds and cultural events arranged by the local Native American student organization.