MEXICO CITY — Scientists have found evidence that cavemen near the U.S.-Mexican border were butchering gomphotheres, elephant-like beasts from the Ice Age that had been believed to be nearly extinct in North America by the time humans appeared there.

Researchers from the University of Arizona and Mexico's anthropology institute say they found the bones of two young gomphotheres — along with blades, a scraping tool and stone chips from making spear tips — at an 11,000-year-old site in Mexico's Sonora state.

The finding adds fuel to a debate over whether overhunting by humans helped drive prehistoric animals such as mastodons, North American horses and gomphotheres into extinction, said Vance Holliday, a University of Arizona archaeologist on the team.

"This is the first time we've found gomphotheres and humans together in North America," Holliday said. "Maybe they killed it, maybe they scavenged it, but it's something completely new."

Gomphotheres are distant relatives to elephants but had wide snouts and long jaws like a crocodile. They stood 9 feet tall. Some varieties had four fearsome-looking tusks, though the species found in Sonora had only two. Gomphotheres were common in North America 12 million to 2 million years ago, then began declining in number.

They survived longer in South America, and there is evidence that humans hunted them there, said Guadalupe Sánchez, an archaeologist at Mexico's National Institute of Anthropology and History and one of the dig's leaders.

In North America, gomphotheres were mostly gone by the time the first humans arrived, probably about 14,000 years ago.

"This is the first kill site I've ever heard of in North America. That's a pretty important discovery," said David Lambert, a gomphothere specialist at the Louisiana School of Science, Mathematics and the Arts. Gomphotheres liked wet, coastal areas — places that probably disappeared under water when the Ice Age glaciers melted. That makes it hard to trace gomphotheres' contact with humans, Lambert said.

Sánchez said the bones were discovered in 2007 at the site, which was given the code name "World's End" to protect its exact location from scavengers who might steal the fossils.

Researchers originally thought they had found mastodons, Sánchez said, but this summer, they uncovered teeth and a jaw that confirmed the animals were gomphotheres. Radiocarbon-dating confirmed the bones are from 11,000 years ago, the same era as the encampment, Sánchez said.

The researchers presented their findings in October at the annual meeting of the Geological Society of America in Portland, Ore.

Sánchez said researchers need to find more sites before knowing whether gomphotheres were widely hunted.

"I don't think there's enough evidence yet to show that people wiped out the animals," Holliday said. "It's a raging controversy, though."

http://www.usatoday.com/tech/science/discoveries/2009-11-08-mexicobeast_N.htm