Humans inhabited Americas 130,000 years ago: study

Humans may have inhabited the Americas about 115,000 years earlier than previously thought, a new study has found.
Archaeologists discovered preserves of 130,000-year-old bones and teeth of a mastodon - an ancient extinct relative of elephants - in California, US, that show evidence of modification by early humans.
Analysis of these finds dramatically revises the time- line for when humans first reached North America.
"This discovery is rewriting our understanding of when humans reached the New World," said Judy Gradwohl, president of the San Diego Natural History Museum, whose paleontology team discovered the fossils.
"The evidence we found at this site indicates that some hominin species was living in North America 115,000 years earlier than previously thought," said Gradwohl.

Until recently, the oldest records of human sites in North America generally accepted by archaeologists were about 14,000 years old.

However, the new fossils were found embedded in fine- grained sediments that had been deposited much earlier, during a period long before humans were thought to have arrived on the continent.
Since its initial discovery in 1992, this site has been the subject of research by top scientists to date the fossils accurately and evaluate microscopic damage on bones and rocks that researchers now consider indicative of human activity.
In 2014, James Paces, a researcher with the US Geological Survey, used state-of-the-art radiometric dating methods to determine that the mastodon bones were 130,000 years old, with a conservative error of plus or minus 9,400 years.

"The distributions of natural uranium and its decay products both within and among these bone specimens show remarkably reliable behaviour, allowing us to derive an age that is well within the wheelhouse of the dating system," said Paces, co-author of the research published in the journal Nature.
The finding raises intriguing questions about how these early humans arrived there and who they were, researchers said.