Theories why mammoths became extinct

For example, overkill may have reduced the populations of certain species to the point that recovery was impossible, which seems to be happening with a number of endangered species in this century.

Or, hunting activity might have overlapped with migration route or mating seasons in a devastating combination. But this is hard to prove on the basis of paleontological evidence, and MacPhee remains skeptical.

Finding numerous samples of well-preserved mammal remains is the first challenge, one of the reasons that MacPhee turned to Wrangel Island. Because Wrangel is a nature preserve, the American scientists agreed not to bring specimens back to the U. Instead, they carried drilled-out bone specimens for radiocarbon dating and molecular analysis.

Each specimen is radiocarbon dated to make sure it coincides with the time of species extinction. Recently, scientists at Penn State report that they have sequenced the genome genetic sequence of the woolly mammoth. Comparing this genome with that of current-day African elephants will help to determine if the mammoth sequence has any potential contaminants from organisms such as bacteria or fungi.

MacPhee co-authored a study on native rats on Christmas Island in Australia that became extinct due to infectious hyperdisease. Black rats, invading from ships starting in , came onto the island carrying fleas that served as a host for disease.

The infection these fleas carried crossed over to native rats, killed their population, and rendered them extinct by In , a reindeer hunter discovered a baby mammoth preserved in the permafrost of the Russian Arctic. MacPhee also agreed to answer our questions about mammals.

Answers from Ross MacPhee. But a new study shows the catastrophe was really caused by a massive decrease in oxygen. The last week of January brought wild weather to the Norwegian arctic island archipelago of Svalbard and its largest town, Longyearbyen. A new cross-disciplinary study provides a comprehensive look at the effects of this extreme weather event on everything from town infrastructure to the natural environment.

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Some scientists are convinced the mammoth became extinct after a comet impact caused extreme changes in the weather on Earth. A new study questions this theory. Illustration: Charles R. Irene Berg Petersen. January - However, scientists behind a new study reject this claim. Scoria droplets from the site in Syria investigated by the scientists behind the new study. Photo: Don Davis. Researchers' Zone:. Powered by Labrador CMS. Scientists think it was a buildup of ice over time.

The next year that would be built on, built on and built on. And the thing about snow is that it kind of makes its own weather. If you have snow it gets very cold! And that preserves the snow pack for a very long time.

The weight of that snow would compact into ice, eventually covering parts of the world in great sheets of ice. It might help to think of the process as a little bit like what happens when you have a favorite sledding hill: the snow is light and fluffy when you start, but if you sled down it enough times and walk up the hill, too , eventually the paths get icy from the footsteps and sleds continually packing the snow down.

It wasn't just ice sheets that were a feature of the ice age. All of that water caught up in the ice made sea level drop feet lower than it is now. That exposed lots of land that is now covered in water, including a land bridge connecting Alaska and Russia! This land bridge allowed a number of species to move into North America from Asia, like bison.

And some North American animals went into Asia, like camels and horses! Bear species traveled in both directions. Humans also used the land bridge to migrate into North America, though scientists think some early humans probably used boats too.

Mammoths also migrated over that land bridge! They originated in Asia and came into North America. But there were other species of megafauna that roam the landscape as well, like giant condors, saber toothed cats and even giant sloths.