How Do Species Evolve?
January 23, 2009--Two hundred years after Charles Darwin's birth, National Geographic-supported scientists are discovering evidence of evolution in action in living things the world over.
In the southeastern United States, fire ants annoy humans, but can be deadly to lizards—just 12 ants could kill this one (photographed in Alabama in June 2008). The stinging ants arrived from South America in the 1930s. Since then, fence lizards in Alabama have evolved longer legs—and a better sense of when to run—than their cousins that live where the lethal ants haven't arrived. Lizards from an ant-free site in Arkansas tend not to run when attacked by ants in experiments. They "hunker down and close their eyes," Pennsylvania State University says biologist Tracy Langkilde. (Read the full story.)
--Helen Fields for National Geographic magazine.
—Photograph by Tracy Langkilde
