New York - Scientists say they've found evidence that stone tips for spears were made much earlier than thought, maybe even created by an earlier ancestor than has been believed.Both Neanderthals and members of our own species, Homo sapiens, used stone tips - a significant development that made spears more effective, lethal hunting weapons. The new findings from South Africa suggest that maybe they didn't invent that technology, but inherited it from their last shared ancestor, Homo heidelbergensis.The researchers put the date of the South African stone tips at about half-a-million years ago - 200 000 years earlier than other research has suggested.The new study involved analysing stone points, a bit less than 8cm long on average, that had been excavated about 30 years ago. EvidenceScientists had previously estimated they were about 500 000 years old, but it wasn't clear whether they were used as spear tips or some other kind of tool, said Jayne Wilkins, a researcher at the University of Toronto and lead author of the new report.She and her co-authors looked for evidence that the artefacts were spear tips, focusing on the way they were shaped and fractured. The pattern of damage along their edges fit in with what researchers found when they made copies of the artefacts and thrust them into the carcasses of antelopes.From the age of the stone tips, the researchers suggest the technology may have been used by Homo heidelbergensis.Sally McBrearty, an anthropology professor at the University of Connecticut who was not involved in the study, said it's clear that the South African artefacts are spear points. She said she sees no logical reason to doubt the trove is 500 000 years old, but she said she'd like to see some firmer proof."I would be happy to say that this is really half-a-million years old, I just want to be sure that it is," she said.There's some room for doubt because of assumptions required in the dating technique and the geology of the South African site where the points were found, she said. Further sampling and analysis could firm up the evidence for the age, she said.