The land bridge still exists today, but is immersed under water. When sea levels were lowered by 330 feet, a 1000 mile wide strip of land was exposed. It surfaced and submerged many times throughout the Ice Age, and is believed to have been exposed for much of the time between 75,000 - 11,000 years ago. .
This land bridge was the route of migration for many a variety of mammals crossing between Asia and North America. Some of the animals arrived long before the glaciation of North America. The animals that migrated to this continent adapted to their new surroundings. Many of the animals living on the continent were herbivorous and extremely large compared to the present fauna. These huge, plant eating animals are called the mega fauna. Some of the most well known mega fauna are the Probocidea. Animals with trunks, which include the mastodon (Mammut) and the mammoth (Mammuthus) of the Ice Age, and the two modern species of elephants, belong in the order Proboscidia. The mastodon probably traveled alone rather than in a herd, browsing on Spruce limbs in open woodlands. The mammoths migrated into North America by at least 1.7 million years ago (Haynes, 1991). They traveled in herds and generally grazed in vast grasslands. .
A new mammoth species evolved from the original mammoths as they migrated from Eurasia, over the Bering Land Bridge, leaving substantial populations in Beringia as they progressed southward. This new species was called the Columbian mammoth (Mammuthus columbi). The Columbian was a larger mammoth well adapted for the North American grasslands. While the Proboscidea originated in Asia and Africa and migrated to North America, other animals evolved in the New World and traveled across the land bridge in the opposite direction from North America to Eurasia. .
Among the genera that originated in the New World was the horse (Equus). Horses migrated to Asia and Europe during a period when the land bridge was exposed.
