gpronger (1142181) writes "The journal Nature reports that newly discovered tool marks on bones indicates that we were using tools at minimum 800,000 years earlier than previously discovered. This places the start of tool use at 3.4 million years ago or earlier. The most likely ancestor in this time frame would be Australopithecus afarensis.
The researchers, led by palaeoanthropologist Zeresenay Alemseged of the California Academy of Science, San Francisco,and Shannon McPherron, (an archaeologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany) state that cut marks on the bones of an impala-sized creature and another closer in size to a buffalo, indicate butchering of the animals by our distant ancestors. However, they do not believe that they were in fact hunters, more likely scavenging the remains left behind by large predators."
Link to Original Source