Photo: Comets Didn't Wipe out Sabertooths, Early Americans?



North America's Great Lakes (pictured in an aerial shot on May 4, 2002) were created during glacial retreats and advances over millions of years—including the brief cold snap called the Younger Dryas, which occurred about 12,900 years ago.

What caused the cold snap, though, has proved controversial: Recent research has weakened a theory that a giant comet caused the drop in temperatures and wiped out much of North America's wildlife, scientists said in October 2009.

Photograph courtesy Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC


NEWS FEEDS    After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed. After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed.

Get our news delivered directly to your desktop—free.
How to Use XML or RSS

ADVERTISEMENT

NATIONAL GEOGRAPHIC'S PHOTO OF THE DAY

50 Drives of a Lifetime

Listen to your favorite National Geographic news daily, anytime, anywhere from your mobile phone. No wires or syncing. Download Stitcher free today.