The Pleistocene, the geologic era immediately preceding our own, was an age of giants. North America was home to mastodons and saber-tooth cats; mammoths and wooly rhinos roamed Eurasia; giant lizards and bear-sized wombats strode across the Australian outback. Most of these giants died at the by the end of the last Ice Age, some 14,000 years ago. Whether this wave of extinctions was caused by climate change, overhunting by humans, or some combination of both remains a subject of intense debate among scientists.
Complicating the picture, though, is the fact that a few Pleistocene giants survived the Quaternary extinction event and nearly made it intact to the present. Most of these survivor species found refuge on islands. Giant sloths were still living on Cuba 6,000 years ago, long after their relatives on the mainland had died out. The last wooly mammoths died out just 4,000 years ago. They lived in a small herd on Wrangel Island north of the Bering Strait between the Chukchi and East Siberian Seas. Two-thousand years ago, gorilla-sized lemurs were still living on Madagascar. A thousand years ago, 12-foot-tall moa birds were still foraging in the forests of New Zealand.
Unlike the other long-lived megafauna, Steller’s sea cows, one of the last of the Pleistocene survivors to die out, found their refuge in a remote scrape of the ocean instead of on land. The sea cows were relatives of the manatee and dugong. Unlike those two species, they were adapted to living in frigid Arctic waters. They were also much larger, growing to be as long as 30 feet from tail to snout, versus 10 for a manatee. Before the Ice Age, they seem to have been ubiquitous along the edge of the Pacific, living everywhere from Japan to the Baja Peninsula. By the 18th century, when they were first made known to Western science, the sea cows were confined to waters surrounding two tiny Arctic Islands in the Commander Chain, in between the Aleutians and the Kamchatka Peninsula.