Northern Extinction: Alaskan horses shrank, then disappeared

Toward the end of the last ice age, a group of horse species that lived in Alaska shrank in body size over several millennia before going extinct. That finding implicates changing environmental conditions as the stimulus for equine die-offs in the region, one researcher suggests. Some scientists previously proposed that the arrival of human hunters was to blame for the demise of many species of large North American mammals (SN: 12/4/99, p.