Colliding tectonic plates pushed up a strip of land from the watery abyss that once divided North and South America, forming the isthmus of Panama. But a study now hints that this happened millions of years earlier than scientists had thought. Evolutionary and population-genetics data from Eciton army ants, which can only travel on dry ground, suggest that the isthmus formed 4–8 million years ago. The research, published on 25 October in Molecular Ecology1, challenges the long-held idea that the link between continents emerged no more than 3 million years ago.
“Our genomic data is very strong evidence that the army ants crossed this region much earlier in time than the model of the simple closure of the isthmus suggests,” says Corrie Moreau, associate curator at the Field Museum in Chicago, Illinois, and co-author of the study. She notes that recent geological studies have also hinted that the isthmus may have emerged earlier than 3 million years ago.
Via Integrated DNA Technologies