“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.”
Controversial study claims humans reached Americas 100,000 years earlier than thought, Ewen Callaway, Nature News
A letter to Nature, from Tom Deméré, Steve Holen, and colleagues, carries a wildly provocative title: “A 130,000-year-old archaeological site in southern California, USA.”
Nature does not usually bother to point out in a title when the “California” being discussed is in the present-day USA. But when we are talking about genus Homo possibly being present in southern California, some 130.7 ± 9.4 thousand years ago, specifying that this is yes, the Americas, is worth doing.
At a site near San Diego, excavated back around 1992, a fossil skeleton for a single mastodon was discovered, together with five large cobbles. The cobbles are proposed to be human artifacts — hammerstones and stone anvils. The mastodon bones, to show signs of being intentionally broken.
The publication comes after recently-conducted dating of the mastodon bones, to 130 thousand years ago. This date is so early as to change the human species thought to have first populated the Americas.
Their contention, if correct, would force a dramatic rethink of when and how the Americas were first settled — and who by. 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.
Controversial study claims humans reached Americas 100,000 years earlier than thought, Ewen Callaway, Nature News
Here is the conclusion of the paper.
We conclude that the reliably dated Cerruti Mastodon site constitutes an in situ archaeological association based on: a clearly defined and undisturbed stratigraphic context; comparative taphonomy; bone modifications like those produced by Palaeolithic percussion technology and replicated by experimental archaeology; presence of hammerstones and anvils that exhibit use-wear and impact marks; and presence of rock fragments that can be refitted to breakage scars. Bone breakage for marrow extraction and/or bone and molar tool manufacture is the preferred archaeological interpretation of the CM site, as there is no evidence of butchery. Concordant interdisciplinary lines of evidence from this study suggest the presence of Homo in North America during the last interglacial (MIS 5e) and as early as approximately 130 thousand years ago (ka) (Supplementary Information 9). This discovery calls for further archaeological investigation focused on North American strata of early late Pleistocene age.
Here are some extracts from the media coverage.
The stone tools found are similar to those used over 1m years ago in Africa, by Homo erectus, an ancestor of Homo sapiens, and dissimilar to the precisely crafted tools of the Clovis culture typical of other early-human discoveries in North America, a fact which has long been a source of speculation about the true nature of the Cerutti mastodon site. Unfortunately, no organic material remains in the bones, so they cannot be radiocarbon-dated.
It is this lack of a reliable date which the new paper addresses. A second attempt, made a few years ago using a method called optically stimulated luminescence to examine some of the site’s sediment, hinted that it was at least 60,000 years old. Dr Deméré and his colleagues therefore brought a third technique, uranium-thorium dating, to bear on the matter. They used this to date fragments from several of the mastodon’s bones. All agreed it had died about 130,700 years ago, give or take 9,400 years. If the cobbles at the site really are stone tools, then, the history of America’s colonisation by early man will have to be rewritten.
The first humans in America may not have been Homo sapiens, Economist
One of the main critiques is that the study doesn’t definitively rule out natural causes for the presence of the purported stone tools, the breakage patterns in the mastodon bones, or the patterns of breakage and wear on their surfaces.
For one, the paper doesn’t satisfyingly rule out the possibility that natural processes carried the large rocks to the scene, says Vanderbilt University archaeologist Tom Dillehay. Nor does it fully rule out the possibility that the wear patterns on the stones were a result of rocks bumping against one another in a stream, he says.
“When you put the total package together, there’s certainly more evidence to reject [the study] than accept it,” Dillehay says.
It’s not impossible that human history in the Americas is older than currently thought, says Southern Methodist University archaeologist and National Geographic grantee David Meltzer, an expert on early Americans.
“But to prove it, you cannot take broken bones and nondescript stones to make the case, not without demonstrating that nature could not have broken those bones and modified those stones,” he says.
Humans in California 130,000 Years Ago? Get the Facts, Michael Greshko, National Geographic
The mastodon fossils looked very different from the other bones nearby. The animal’s limb bones, molars and tusks had been smashed into many pieces. That struck the researchers as odd, because leg bones are strong and thick and should have been preserved over the eons — especially since more fragile ribs and vertebrae had survived in much better shape.
“It was a really intriguing site,” said study co-author Tom Deméré, a vertebrate paleontologist at the San Diego Natural History Museum, pointing to the patterns that defied an explanation by natural causes.
The ends of some bones had been torn off — a sign that humans may have been trying to reach the bone marrow. The mastodon bones also bore the spiral fracture patterns that are typical of breaks that happen when the bone is still fresh, rather than the straight ones that tend to mark older bone broken much longer after death. (The wolf and horse bones in nearby sediment layers did not exhibit the same patterns.)
That strange, selective destruction is a sign that humans were there, targeting the thick bones and tusks that could be shaped into new tools, the study authors said.
130,000-year-old mastodon bones could rewrite story of how humans first appeared in the Americas, Amina Khan, Los Angeles Times