When did the first humans reach the Americas? The answer to this question is highly controversial. Findings in New Mexico are now providing new evidence that the first representatives of Homo sapiens had settled on this continent around 36,000 years ago – long before the end of the last Ice Age. Evidence of this are traces of processing on mammoth bones and the remains of campfires with bone meal as fuel.
For a long time, the Clovis culture, which spread around 13,000 years ago in North America, was considered the earliest human population on the American continent. Stone tools of typical design and fossil relics of the Clovis people have been preserved at many sites in North America. According to current theory, the ancestors of these indigenous people crossed the Bering Strait between Asia and North America around 15,000 years ago. When the great inland ice sheet over North America began to thaw at the end of the last ice age, these people were able to advance south from Alaska through an ice-free corridor and spread across the continent.
More and more indications of an earlier arrival
However, some recent discoveries raise doubts about this scenario. Because in several places in North and South America, archaeologists have now discovered possible evidence of a human presence that is far older than the Clovis culture. These include stone blades, points and flakes discovered in Mexico that are around 30,000 years old. Animal bones of similar age have been discovered in Uruguay, potentially bearing man-made scratch marks. And in the US state of New Mexico in 2021, researchers uncovered 23,000-year-old human footprints — the oldest footprints on the American continent.
Also in New Mexico, researchers led by Timothy Rowe from the University of Texas at Austin have now discovered further evidence of an early presence of homo sapiens in America. The starting point was the discovery of a pile of heavily fragmented bones on Rowe’s property, which turned out to be mammoth bones. Dozens of broken bones from two woolly mammoths were found next to a crushed skull. “It’s not a charismatic site with a neatly laid out skeleton, it’s quite a mess,” says Rowe. The multitude of damaged, fractured bones and their disorderly distribution suggested subsequent disturbance of the cadavers—possibly by early humans.
Mammoth bones with clear machining marks
To find out whether these mammoths might have been killed and dismembered by early humans, the scientists analyzed the finds using a variety of high-tech methods, including micro-computed tomography, spectrometry, scanning electron microscopy and chemical analysis. In doing so, they came across conspicuous circular holes in many of the bone fragments, which at first glance could be traced back to predator teeth – but their shape did not match them: “Predator bite marks are widest on the outside and narrow towards the inside to a single point,” explains the team . “But these holes were narrowest on the surface of the bone and widened inwards.” Such marks are typical of a pointed tool that is drilled into the bone and then moved back and forth to extract fat and marrow from the inside, for example.
Further evidence of processing was found in bone chips – flat fragments from the hard shell of the limb bones. “These flakes show an extraordinary pattern that geological processes or animal feeding cannot explain,” Rowe and his colleagues report. Because almost 80 percent of these bone fragments had been knocked off exactly parallel or perpendicular to the line of the bones. “We considered scavenging, trampling, and other non-human factors, but it proved extremely unlikely that this thorough, systematic, and highly structured destruction of the bones was caused by such factors,” the scientists explain. In their opinion, these bone flakes were made by humans in order to use them as tools, for example.
At least 36,000 years old
Chemical analyzes of microparticles from the site provided further indications of human impact. They consisted of ashes, charcoal, ground bone powder and the remains of burned fish scales, bones and other small animals. “The fish relics are remarkable because the site is about 70 meters from the nearest river,” Rowe and his colleagues report. Bones and bone meal are also typical fuels in many archaeological fireplaces. “The site presented itself initially as a possible battle site of the Clovis culture,” according to the archaeologists.
But when the researchers dated the mammoth relics using five different variants of radiocarbon dating, the surprising result was that the bones are between 31,000 and 38,000 years old, depending on the dating method, with an age of 36,000 to 38,000 years being the most likely. The bones thus date back at least 15,000 years before the arrival of the Clovis people. “These finds thus set a new point of reference for the settlement of America,” state Rowe and his team. So there must have been a population of immigrants there long before the end of the Ice Age and the Clovis culture.
Source: University of Texas; Article: Frontiers in Ecology and Evolution, doi: 10.3389/fevo.2022.903795