The discovery is detailed in a new study, published online March 24 in .When the makers of these tools were using the site (from 15,500 to 13,200 years ago), the region would have been slightly cooler than it is today, probably by an average of about 5 to 6 degrees Celsius—"rather amiable at that time period," Lee Nordt, of Baylor University's Department of Geology and co-author of the new study, said in a press briefing on Wednesday.“You’ve got all these different records all scattered around the planet and nobody’s known how to link them all in,” says Turney. We already have an independent carbon-14 record that came from analysing tree rings, but it stretches back only 12,655 years.The Lake Suigestu data will extend that accurate record to 60,000 years before the present.
The trouble is that the atmospheric ratio of carbon-14 to carbon-12 changes over time, making it difficult to establish exactly how much was in the organism when it was alive, and making the time-of-death calculation less accurate. Every year for at least the last 60,000 years, a layer of algae has formed on the lake bed.But the resources in the area were likely plentiful, added Michael Waters, of the Center for the Study of the First Americans at Texas A&M University in College Station and co-author of the new study.With the rich hill country around them, "it's not surprising people came back time and time again." The people who left the tools and fragments described in the study were likely hunter–gatherers, passing through the site from time to time over thousands of years.But stone tools found submerged in a sinkhole on a river Florida suggest humans were living in America up to 1,500 years than previously believed - and hunted mastadon and may even have have pet dogs.Stone tools, including a sharp biface knife (pictured) have been found in a sink hole beneath a river in Florida.
“This is massively important,” says Chris Turney, a climate scientist at the University of New South Wales in Sydney, Australia, who was not involved in the research.