A study that claims humans reached the Americas 130,000 years ago – much earlier than previously suggested – has run into controversy.
Humans are thought to have arrived in the New World no earlier than 25,000 years ago, so the find would push back the first evidence of settlement by more than 100,000 years.
The conclusions rest on analysis of animal bones and tools from California. But many experts contacted by the BBC said they doubted the claims.
Thomas Deméré, Steven Holen and colleagues examined material from the Cerutti Mastodon site near San Diego. The site was originally uncovered in 1992, during highway construction work. Possible stone tools were discovered alongside the smashed up remains of a mastodon (Mammut americanum) – an extinct relative of mammoths and living elephants.
The researchers behind the latest study were unable to carry out radiocarbon dating on the remains, so they used a technique called uranium-thorium dating on several bone fragments, coming up with a date of 130,000 years.
The team members found that some of the bones and teeth bore a characteristic breakage pattern known as spiral fracturing, considered to occur when the bone is fresh. Additionally, some of the bones showed typical signs of being smashed with hard objects.
Rocks found alongside the mastodon remains show signs of wear and being struck against other surfaces, the researchers say. They conclude that these represent hammerstones and anvils – two types of stone tool used by prehistoric cultures.
Dr Deméré, curator of palaeontology at the San Diego Natural History Museum, said the totality of evidence at the site had led team members to the conclusion that “humans were processing [working on or breaking up] mastodon limb bones using hammerstones and anvils and that the processing occurred at the site of burial 130,000 years ago”. Via BBC