Genes, Not Man, Killed Mammoths

Jun 11, 01:16 PM

Current Headlines: By THOMAS H. MAUGH II, SPECIAL FROM THE LOS ANGELES TIMES

Paleontologists long have assumed that massive hunting by humans led to the extinction of the woolly mammoths about 12,000 years ago, but new genetic analysis indicates that inbreeding and loss of genetic variability was the actual cause.

Paleontologists Ian Barnes of the University of London, Adrian Lister of University College London and their colleagues studied mitochondrial DNA samples from 96 bone, tooth and ivory specimens collected primarily in Alaska and Siberia.

Their findings, published Thursday in Current Biology, chart the animals' evolutionary history.

The animals apparently originated in Asia about 150,000 years ago, migrating over the land bridge connecting Siberia to Alaska in what is now the Bering Strait to form populations on two continents.

A gradual warming of the Earth caused sea levels to rise, inundating the bridge and isolating the two groups, which became genetically distinct.

About 100,000 years ago, the land bridge opened again, allowing the two groups to intermingle. By about 43,000 years ago, the Siberian lineage had died out, leaving only the Alaskan contingent.

The ice age 20,000 years ago then stressed the population further, the researchers said, reducing their viability.

The massive 9-foot-tall creatures with their 20-inch-long hair and gigantic curved tusks long have been an icon for the frozen tundra of the last ice age and the battles of humans to find meat for their families.

Their thick, shaggy hair, small ears to minimize heat loss and an extra layer of fat around their bodies helped them survive the cold, but did little to prevent their ultimately dying off.

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