The size and shape of the tusk plays a role in determining the species of the mammoths at Tolo Lake. For example, the Columbian mammoth has a very long set of curved tusks while the Woolly mammoth has shorter and more curved tusks. The tusks discovered at Tolo Lake measure seven feet along the curve and most likely belong to the Columbian mammoth. It was during this time period that sheets of glacial ice up to 2 miles thick covered most of northern North America, northern Europe, and parts of Asia. Because so much water became ice, sea level fell about 350 feet and the shallow Bering Strait became a land bridge allowing many animals and the first Native Americans to cross into the New World.
Bison are among the animals that crossed the Bering Strait at about the same time as the Mammoths.
Remains of these bison have also been found at Tolo Lake. Some scientists think that hunting by man caused the mammoths and many other large animals to become extinct. Others believe that the cause was climatic change. Researchers at the Tolo Lake site hope to find evidence that supports these theories. It was once thought that mammoths became extinct more than 10,000 years ago.