Modern subspecies are descended from elk that once inhabited Beringia, a steppe region between Asia and North America that connected the two continents during the Pleistocene. Beringia provided a migratory route for numerous mammal species, including brown bear, camel, horse, caribou, and moose, as well as humans. As the Pleistocene came to an end, ocean levels began to rise; elk migrated southwards into Asia and North America. In North America they adapted to almost all ecosystems except for tundra, true deserts, and the gulf coast of the U.S. The elk of southern Siberia and central Asia were once more widespread but today are restricted to the mountain ranges west of Lake Baikal including the Sayan and Altai Mountains of Mongolia and the Tianshan region that borders Kyrgyzstan, Kazakhstan, and China's Xinjiang Province. The habitat of Siberian elk in Asia is similar to that of the Rocky Mountain subspecies in North America. During the Late Pleistocene their range was much more extensive, being distributed across Eurasia, with remains being found as far west as France. These populations are most closely related to modern Asian populations of the elk. Their range collapsed at the start of the Holocene, due to them being specialized to cold periglacial tundrasteppe habitat, which was largely replaced with closed forest, being outcompeted by red deer in these conditions. Relictual populations survived into the early Holocene in southern Sweden and the Alps, where the environment remained favorable.