“Do you think whales ever walked the earth?”
I thought the captain of a whale-watch boat in Monterey Bay was asking a trick question. But it’s no riddle—it’s a scientifically documented, evolutionary fact.
The largest creatures on the planet, whales are classified–along with dolphins and porpoises–as cetaceans, from an ancient Greek word for “sea monster.” However, they descended from rather humble four-legged mammals that hunted and fished along the riverbanks of what is now Pakistan and India.
In one of evolution’s most dramatic U-turns, these land dwellers returned to the ocean from which their ancestors had emerged. In a geological blink—roughly ten million years—they reshaped their bodies for an aquatic life. Fur thinned. Limbs flattened. Tails strengthened. Nostrils began their slow migration to the top of the head. Hooves gave way to flukes
The earliest known whale, Pakicetus, lived about 52 million years ago. The wolf-sized beast, armed with sharp teeth, straddled the line between land and water by wading into rivers and streams to hunt fish. Fossils reveal that its skull enclosed dense, specialized ear bones for underwater hearing, strikingly similar to those of today’s whales.
By about 50 million years ago, the crocodile-shaped Ambulocetus—the “walking whale”–strode on sturdy legs and broad, webbed feet, at home on land or in water. Its spine flexed in powerful waves, signaling a shift from limb-powered paddling to tail-driven propulsion.
Soon after came Rodhocetus, more streamlined and more fully committed to the sea, with a shorter neck and stronger tail muscles. Its nostrils had begun to creep backward along the snout–a preview of the blowhole.
By about 40 million years ago, “modern” whales ruled warm seas, their long bodies driven by horizontal tail flukes. Hind limbs had shrunk into tiny, detached bones–no longer useful for walking but retained as anchors for reproductive muscles. With blowholes, whales could breathe without breaking stride, remaining submerged and leaving barely a ripple at the surface.
Two different feeding systems evolved to meet the demands of increasingly large bodies. Toothed whales, such as orcas and belugas, use conical teeth to seize and swallow prey. Bigger and bulkier, baleen whales–including blues, grays and humpbacks–gulp immense volumes of water into their cavernous mouths. Rows of baleen hanging from their upper jaws filter out krill, anchovies and other small organisms before the water is expelled.
Whales’ greatest challenges, however, have come from humans. Large-scale commercial hunting intensified in the late nineteenth century with the development of explosive harpoons and steam-powered ships. California’s gracious grays were a prime target. Oil rendered from their blubber fueled lamps, lubricated machinery and softened soap; their baleen was fashioned into corsets, umbrellas and buggy whips.
The International Whaling Commission, formed in 1946, banned commercial hunting. With the passage of the U.S. Marine Mammal Protection Act and the Endangered Species Act in the 1970s, gray whale numbers rebounded–one of the great conservation success stories of the twentieth century.
But in recent years, a more insidious crisis has unfolded. Since 2018, scientists have documented widespread strandings and deaths of gray whales along the Pacific coast. Many of the animals are emaciated, likely suffering from diminished food supplies linked to climate-driven changes in their North Pacific and Arctic feeding grounds. Over the past decade, the eastern North Pacific gray whale population has declined by roughly half.
As World Whale Day approaches on the third Sunday of February, the migration of gray whales along our coast offers a living reminder that evolution’s ancient story is still unfolding, just offshore. You can learn more about these magnificent creatures and how to help them from organizations such as the American Cetacean Society, Marine Mammal Center and Save the Whales.
If you live near the Sonoma Coast, volunteers with the Stewards of the Coast and Redwoods offer interpretation of the grays’ migration at Bodega Head every Saturday and Sunday from 10:00 a.m. to 2:00 p.m. through May (weather permitting).
