The discovery of 56 stone tools four feet underground in the Texas Hill Country makes certain what most archaeologists have suspected for a while - that human beings were in the Americas at least 15,000 years ago.
That date is about 2,000 years before the appearance of the so-called "Clovis culture" whose distinctive fluted and notched arrowheads are the earliest widely found human artifacts in North America.
Evidence for "pre-Clovis" human activity has been accumulating for decades as archaeologists have found a few unusually old sites in places as far apart as coastal Chile and central Pennsylvania.
But there were always problems - a jumbling of deposits, uncertainties of dating - that made some archaeologists doubt the age of those discoveries, Washington Post reports.
The study appears in the April issue of the journal Science.
For the last 100 years, archeologists have believed that the Clovis people were the first to enter the Americas about 13,000 years ago. Artifacts found by this study now place that time back 2,500 years, or to about 15,500 years ago.
At the Debra L. Friedkin archeological site, located about 10 miles outside of Salado in Central Texas, the Baylor researchers, along with their colleagues, found nearly 16,000 artifacts that predated the Clovis people.
Most the artifacts were chipping debris from the making and reshaping of tools, however, about 50 artifacts were tools themselves such as knives and projectile points.
The dating process placed these artifacts back to about 15,500 years ago. This find is not only the earliest evidence of human occupation in North, South and Central America, it also has the largest number of artifacts dating to the pre-Clovis time period, Baylor University reports.