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.