Many scientists had assumed our early human ancestors ate only meat they stripped from animals that had died from natural causes or had been left behind by lions, leopards and other carnivores.
But anthropologist Henry Bunn of the University of Wisconsin argues those ancestors were capable of ambushing herds of large animals after carefully targeting individual animals for slaughter, Britain's The Observer newspaper reported.
"We know that humans ate meat 2 million years ago," Bunn, speaking in Bordeaux, France, at the annual meeting of the European Society for the study of Human Evolution, said.
"What was not clear was the source of that meat. However, we have compared the type of prey killed by lions and leopards today with the type of prey selected by humans in those days. This has shown that men and women could not have been taking kill from other animals or eating those that had died of natural causes.
"They were selecting and killing what they wanted," Bunn said.
That finding should mean a major reassessment of our ancestor's hunting history, he said.
"Until now the oldest, unambiguous evidence of human hunting has come from a 400,000-year-old site in Germany where horses were clearly being speared and their flesh eaten. We have now pushed that date back to around two million years ago."