Evolution World Tour: Wadi Hitan, Egypt || Smithsonian Magazine
Scientists had long suspected that whales were terrestrial mammals that had eased into the ocean over millions of years, gradually losing their four legs. Modern whales, after all, have vestigial hind leg bones. But little in the fossil record illustrated the transition—until Gingerich began excavating Wadi Hitan’s hundreds of whale fossils, finding legs and knees.
Those skeletons “are the Rosetta stones,” says Nick Pyenson, a curator of fossil marine mammals at the National Museum of Natural History. “It’s the first time we could say we know what the hind limbs of these animals look like. And they’re bizarre.” Older specimens of footed whales have since been identified, but Wadi Hitan’s are unmatched in their numbers and state of preservation. The valley—about a three-hour drive from Cairo—is now a Unesco World Heritage site visited by some 14,000 people each year.
Gingerich speculates that whales’ landlubber ancestors were deer- or pig-like scavengers living near the sea. About 55 million years ago, they started spending more time in the water, first eating dead fish along the shore, and then chasing prey in the shallows, and then wading deeper. As they did, some evolved traits that facilitated hunting in water. Over time—since they no longer had to bear their full body weight at sea—they got bigger, their backbones elongating and their rib cages broadening.
