Discover Magazine dark matter
Your hands are, roughly speaking, 360 million years old. Before then, they were fins, which your fishy ancestors used to swim through oceans and rivers. Once those fins sprouted digits, they could propel your salamander-like ancestors across dry land. We know a fair amount about the transition from fins to hands thanks to the moderately mad obsession of paleontologists, who venture to inhospitable places around the Arctic where the best fossils from that period of our evolution are buried. By comparing those fossils, scientists can work out the order in which the fish body was transformed into the kind seen in amphibians, reptiles, birds, and mammals–collectively known as tetrapods. A team of Spanish scientists has provided us with a glimpse of that story. Before getting into the details of the new experiment, leap back with me 450 million years ago. Our own fishy ancestors gradually modified this sort of fin over millions of years. Both fins and hands get their start in embryos.
• General Science Blogs 02