By studying related populations of small fish, called sticklebacks, the scientists have learned how a variety of animals might have lost their hindlimbs during evolution. The researchers discovered that relatively small changes in the regulation of specific genes can lead to a phenomenon called hindlimb reduction. The work demonstrates that rapid skeletal changes can occur in one body structure without disrupting the essential role of the same genes elsewhere in the body.

The research team, led by Howard Hughes Medical Institute investigator David M. Kingsley, published its findings in the April 15, 2004, issue of the journal Nature. Kingsley and his colleagues at the Stanford University School of Medicine collaborated on the studies with researchers from the Fred Hutchinson Cancer Research Center, the Institute of Freshwater Fisheries in Iceland and the University of British Columbia.

"One of the central mysteries of evolutionary biology has been the relationship between microevolution and macroevolution," wrote Neil H. Shubin and Randall D. Dahn of the University of Chicago in an accompanying perspective article in Nature. "[The researchers] might have discovered a smoking gun a real example of a type of macroevolutionary change that is produced by genetic differences between populations."

According to Kingsley, hindlimb reduction is a trait that has evolved repeatedly in different animal groups, including mammals, such as dolphins and whales that have returned to the sea, snakes, reptiles, amphibians and many fish species. "It's a major morphological change in the vertebrate skeleton," Kingsley said. "And despite the fact that it has
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
14-Apr-2004