nature & planetanalysisThe Public Domain Review19th century · Arctic
Darwin was mocked for imagining a bear slowly turning into a whale, his example of how natural selection could work
In On the Origin of Species, Darwin speculated that a bear might, through natural selection, become more and more aquatic, catching insects with a wide-open mouth until it became as monstrous as a whale. He based this on a black bear that the explorer Samuel Hearne had seen swimming and feeding in water. Critics mocked the idea, and Darwin removed the passage after the second edition. The polar bear was a related puzzle: naturalists such as Buffon and Goldsmith linked animal size and colour to climate and food, and James Lamont, who wrote to Darwin, proposed that polar bears evolved from brown bears that learned to hunt seals on the ice. Genetic studies now suggest polar bears and brown bears split about several hundred thousand years ago and have interbred.
It shows how the idea of natural selection grew out of observations about animals and their habitats, and how the early theory was tested against animals as ordinary as bears. Polar bears are now a leading example of how species can adapt to a changing environment.
Polar bears and brown bears can interbreed, and genetic studies have found polar bear ancestry in some brown bear populations.
Image: The Public Domain Review
