When Whales Walked

All too often, evolution is thought of as a trip out of the ocean and into a Toyota Prius, as if Earth's organisms took a distinct path from the water and onto land. This, of course, isn't true--but it's especially not true when it comes to modern whales, which descended from mammals who evolved on land and then ended up heading back to the sea. As a new exhibit at the American Museum of Natural History (AMNH) shows, the “first whale” was actually the Pakicetus attoki, a four-legged, wolf-sized land mammal living 50 million years ago.

The exhibit, which opened last weekend, is called “Whales: Giants of the Deep," and is presented by both the AMNH and Te Papa Tongarewa, the national museum of New Zealand. It covers the history of whales from the present—with special attention paid to the way human beings from New England to New Zealand have relied on, mythologized about and interacted with the whale—all the way back to their prehistoric ancestors who dove for fish in the shallows of ancient seas.

An extensive collection of fossils shows whale ancestors, beginning with Pakicetus attoki, who's shown below. The fossil record leads to Ambulocetus natans, an early whale ancestor who followed shortly after, and whose adaptations made life better in the sea than on land. Ambulocetus had diminished hips and heard through its jawbone, as it lacked external ears.

As the continents and climate changed 35 million years ago, so too did the ocean currents. That allowed whale ancestors to take to the seas. New upwellings, cold seawater rising from depths of the new Southern Ocean, brought rich nutrients to the ocean surface, and supported a multitude of tiny creatures, which in turn became a major food source for whales.

On this diet of tiny creatures–and with the adapted filtration system of baleen in their jaws in lieu of teeth–whales became the largest creatures that the Earth has ever seen. Children are able to crawl through the blood vessels in a life-sized model of a blue whale heart, and the AMNH’s full-sized blue whale model is still lofted above the Milstein Hall, looking more like a blimp than P. attoki.

As for the toothed whales, including dolphins and porpoises, Douglas Adams probably summed them up best in The Hitchhiker’s Guide to the Galaxy where he wrote:

For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.

Rare specimens on tour from the Te Papa Tongarewa’s collection include the beaked whale, and artifacts from New Zealand’s indigenous Maori people, who venerated whales in art and storytelling, such as in the myth of the whale rider.