The Friends of Charles Darwin

Scientists have discovered a genetic basis underlying the evolution of fewer limbs in animals by studying threespine sticklebacks, the journal Nature says. Some sticklebacks have a spine in their pelvic fin to protect against predators but others lost it through evolution. The team compared genetic maps of both types of fish to find places in their DNA code that controlled this feature. The gene Pitx1 was found to map exactly to the part of the genome associated with most variation in the feature. Scientists say the genetic mechanism could be a "smoking gun" for the way rapid changes in body plan can appear over time in the evolution of new animal species. What is more, the mechanism appears to work without the harmful side effects sometimes seen with gene mutations.