Science / Medicine : Salt Linked to Extinctions
A new theory links the extinction of mammoths and mastodons to the disappearance of salt licks in Michigan at the end of the Ice Age.
The idea was put forward by three Michigan researchers who observed that the state’s many salt deposits are situated in the same region in which fossils of the extinct elephants have been found.
Salt deposits are common in the southern half of Michigan’s lower peninsula, which supplies about a quarter of the salt used in the country. Much of it comes from a large salt mine under Detroit. The same region has 203 known mammoth or mastodon sites.
The giant mammals died out between 10,000 and 12,000 years ago, just as Ice Age glaciers were retreating not far to the north of the salt-fossil zone.
The theory, published in the current issue of National Geographic Research, is advanced by Michigan State University zoologist J. Alan Holman. It assumes that the ancient animals resembled their modern relatives and craved salt. Modern elephants travel long distances in Africa for salt, some even venturing deep into caves to gouge out deposits with their tusks.
If mastodons and mammoths did the same, the researchers speculate, they may have trekked from far-away saltless parts of the Midwest, braving the harsh climate of Michigan--then a virtual tundra near the edge of the glacier--to eat salt that was then exposed on the surface. But when the glaciers melted--at about the same time the huge beasts died out--the outwash and its huge load of sediment buried the salt layers.
