Conventional wisdom holds that the first humans arrived in North America at most 25,000 years ago. What if the real date is much earlier? A team of researchers suggests that humans of some sort existed in North America some 130,000 years ago. This claim is based on a reexamination of purported stone tools and broken mastodon bones that were uncovered in the early 1990s. However, not all researchers who have seen the research agree with the findings.
Our tale begins in 1992, when the state of California was building a new highway. Workers uncovered what appeared to be the remains of a large animal, which turned out to be a mastodon. Experts from the San Diego Natural History Museum were dispatched to investigate and exhume any artifacts. What they found at the Cerutti Mastodon site was a collection of mastodon bones and what might be stone tools. The uncertainty over these artifacts is what leads to the controversy regarding the new findings.
In reexamining the materials from the Cerutti Mastodon site, Steven Holen and his colleagues believe they found evidence of human activity. That wouldn’t so unusual as mastodon remains are often found in close proximity to human artifacts. However, the team dated this site to more than 100,000 years before humans are believed to have arrived in the Americas.
The team was unable to date the remains with radiocarbon dating, so they resorted to uranium-thorium dating of multiple bone fragments. This technique is usually used on inorganic samples like cave carbonates and coral, which absorb uranium from seawater. However, organic material like bone can also absorb enough uranium from ground water to be dated.
It’s the conclusions drawn from the artifacts that gives experts pause. The researchers behind the new analysis claim that spiral fracture patterns in the mastodon bones indicate they were broken while fresh, and these breaks are consistent with tool use by humans. They point to several stones that could have been used as hammers and anvils to break the bones, possibly to use pieces of the bones for constructing other tools.
The scientific community seems pleased with the dating methodology, but the presence of humans at the site is a tougher sell. A natural process could have caused damage to the bones, and the alleged tools don’t show undeniable evidence of human use. This is all far from certain, but interesting nonetheless. If this turned out to be accurate, it could mean that Homo sapiens was not the first human species in America. The Denisovans or Neanderthals might have beaten us to the new world.
source : https://www.extremetech.com/extreme/248440-study-suggests-humans-arrived-north-america-100000-years-earlier-thought