 Ancient whales actually had legs. They finally parted company with these appendages about 35 million years ago due to a relatively sudden genetic event, according to an international group of scientists headed up by Hans Thewissen, a professor of anatomy at Northeastern Ohio University's College of Medicine. Thewissan and his team used developmental data from contemporary spotted dolphins and fossils of ancient whates to try and determine exactly what genetic changes could have caused whales, dolphins and porpoises to lose their legs. In point of fact, more than 50 million years ago, ancestors of both whales and dolphins were four footed land animals, rather like large dogs. They eventually became the swimmers we recognize today during the following 15 million years, losing their hind limbs in th eprocess. Whales share common ancestors with hippos, camels and deer remarked team member Martin Cohn, a developmental biologist and associate professor and member of the UF Genetics Institute. He explained that the transition to an aquatic lifestyle occurred long before these animals eliminated their hind limbs. During the transition period, the hind limbs did become smaller. In findings slated to be published this week in the Proceedings of the National Academy of Science, scientists will argue that the gradualr shrinkage of a whale's hind limbs took place over 15 million years, the changes occuring during the fetal stage of whale development. Whales transitioned through a remarkable transformation to become more like ancestral fish. The process itself is remarkable and led to profound consequences in how whales were able to survive. Only in the past five years has a clearer understanding of this development history been had by scientists around the globe. |
