Polar bears diverge from brown bears
A brown bear population isolated on Arctic sea ice becomes a marine predator in a geological instant.
- When
- —
- Duration
- 226 thousand years
- Known to
- ± 300 thousand years
- Era
- Early Pleistocene, Quaternary
Genomic evidence places the divergence of polar bears from brown bears within the Pleistocene, with estimates spanning several hundred thousand years, and the two remain capable of producing fertile hybrids. The changes are rapid and drastic: white fur, elongated skull, hair-covered footpads, and a metabolism adapted to a diet of almost pure fat that would be lethal to most mammals. It is one of the fastest well-documented cases of a large mammal adapting to a new habitat.