It took only 5 million years - an instant in geologic time - for whales to diversify into the vastly different body types seen today, a new study indicates.
Whales evolved explosively fast into a spectacular array of shapes and sizes, a new study suggests.
Whales' sizes stretch the imagination from the 100-foot (30-meter) long blue whale — the largest animal to have ever existed — to a small species about the size of a dog. Many ideas exist for how whales evolved into different body types, but the new study, published online in the May 19 edition of the journal Proceedings of the Royal Society B, is the first attempt to unravel the mystery.
"It's as if whales split things up at the beginning and went their separate ways. The distribution of whale body size and diet still correspond to these early splits," said evolutionary biologist and study co-author Michael Alfaro of UCLA. "Our study is the first to test the idea that evolution in early whales was explosively fast."
Around 35 million years ago, when modern whales began to appear in the ocean, whale evolution ignited. Whales began as basically similar body types and evolved into everything from porpoises to blue whales over the next 5 million years, said study lead author Graham Slater of UCLA.
"Five million years is like the blink of an eye," Slater told LiveScience.
The finding supports what's known as the explosive radiation hypothesis. The idea is that a few key traits allowed the earliest ancestors of modern cetaceans — marine mammals, including whales, dolphins and porpoises — to explore new ways of living. Once these ancestors branched out into a new body form, they stayed the course.
The key traits credited with the explosive evolution include sonar, large brains, baleen (the stringy looking stuff across some whales' mouths that filters small animals from sea water), and complex sociality.