Humans reached America 100,000 years earlier than thought.

Nature reveals the remains of a 130,000-year-old barbecue… that opens a controversial – and way, way older – chapter of human history in the Americas:

Most scientists subscribe to the view that Homo sapiens arrived in North America less than 20,000 years ago. The latest study raises the possibility that another hominin species, such as Neanderthals or a group known as Denisovans, somehow made it from Asia to North America before that and flourished.

“It’s such an amazing find and — if it’s genuine — it’s a game-changer. It really does shift the ground completely,” says John McNabb, a Palaeolithic archaeologist at the University of Southampton, UK. “I suspect there will be a lot of reaction to the paper, and most of it is not going to be acceptance.”

The study focuses on ancient animal-bone fragments found in 1992 during road repairs in suburban San Diego. The find halted construction, and palaeontologist Tom Deméré of the San Diego Natural History Museum led a five-month excavation. His crew uncovered teeth, tusks and bones of an extinct relative of elephants called a mastodon (Mammut americanum), alongside large broken and worn rocks.

“We thought of some possible explanations for this pattern, and the process we kept coming back to was that humans might be involved,” he says. Attempts in the 1990s to date the site suggested that the ivory was some 300,000 years old, but Deméré was sceptical: the method his colleagues used was problematic, and the age seemed so improbable for humans to be living in California.

Deméré’s co-authors Kathleen Holen and her husband Steven Holen, archaeologists at the Center for American Paleolithic Research in Hot Springs, South Dakota, have put forward several sites in the US Midwest as evidence for a human presence in the Americas up to 40,000 years ago. But many scientists have viewed these claims with scepticism.

After hearing about the San Diego mastodon, the Holens visited Deméré in 2008 to see the boxed-up remains. “We were looking at something very, very old, but it had the same fracture patterns that we had seen before,” says Kathleen Holen. The bones looked as though they had been set on a large ‘anvil’ stone and struck with a ‘hammer’ rock. The team contends that the rocks recovered from the site were used either to extract the mastodon’s bone marrow or for making more-delicate bone tools.