The first human inhabitants of North America settled at least 2,000 years earlier than the people previously identified as the first Americans. So say archaeologists, who have unearthed a trove of stone artifacts belonging to the early Americans at an archaeological dig in central Texas, in the U.S. southwest; details of the finds are reported in Science magazine. The ancient stone artifacts were found lying undisturbed at an archaeological site over 60 kilometers southwest of Austin. Michael Waters, director of Texas A & M University's Center for the Study of First Americans, led the dig at the site near the head of a small stream in what's come to be known as the Buttermilk Creek Complex.  
     Waters say the latest relics were buried in a clay layer beneath sediment containing artifacts of the Clovis people, thought to be the earliest American settlers. But Waters say the stone artifacts include a wide variety of tools dating as far back as 15,500 years ago. The dating - which relied on a technique known as optically stimulated luminescence (OSL) that can tell how long minerals have been buried - is robust, says the team. And, they add, the observed sequence is also reliable; the sediments have not been mixed up after the tools were dropped.
     "We found many, many chisel-like tools, indicating that people were working bone, working wood, you know, many hard materials," Waters said. "What is special about the site is that it has the largest number of artifacts dating to the pre-Clovis time period, that these artifacts show an array of different technologies, and that these artifacts date to a very early time," he added.
     Evidence of Clovis people were first discovered in 1932, and ever since, Waters says, archaeologists have argued about whether other sites also belonged to the Clovis civilization or were older, unrelated settlements. The discovery strengthens the case for two theories that traditional archaeologists laughed at not long ago - that the first Americans came earlier than 13,000 years ago, and that they didn't walk over a land bridge into North America from Siberia, but came by skin boats at least 16,000 years ago (or long before) skirting along coastlines of the Aleutian Islands and then Alaska, Canada and America.
     Waters believes they came by boat, hunting seals beside Ice Age glaciers a few miles at a time, surviving Ice Age weather, bringing families and pet dogs. He thinks the first colonies in America sprouted tens of thousands of years ago along the Columbia River basin between Washington and Oregon.
     The tools found in Texas are flint blades small and thin, designed by people who carried everything they owned. It is likely that flint tools made up only 5 percent or so of the belongings of these people. Many of the tools are cutting blades used to whittle and shape bone and wood; there were no distinct spear points. Waters thinks the Buttermilk people used the stone tools to make spear points from bone. Some tools had notches with convex edges - carving tools; some chisels had edges dulled from scraping hard surfaces.
     One artifact gave Waters a thrill when found: a golf-ball-size nodule of hematite, worn flat on several sides the way schoolroom chalk wears flat. Hematite when mixed with animal and plant oils produces red ochre - paint to adorn spear shafts, clothing - or skin. "These people from 15,500 years ago were decorating themselves," he said.
     Rolfe Mandel, a geoarchaeologist with the Kansas Geological Survey, said the Texas discovery is "a very big deal." The Texas discovery upends that, Mandel said, people didn't just enter Alaska and sprint with babies to Texas; they migrated, perhaps for centuries.
     On the other hand, professor Dillehay, from Vanderbilt University in Tennessee, said that the OSL technique used by Waters was less reliable than radiocarbon dating, which has been applied to other early American sites. And assigning the artefacts to Clovis and pre-Clovis technologies was not straightforward because the site lacked the projectile points required to reliably distinguish between the two. In addition, said the Vanderbilt anthropology professor, the tools come from a floodplain deposit that is just 6-7cm thick. This, he said, was "potentially problematic" because of the possibility that artefacts were transported around by water.
     Professor Gary Haynes, from the University of Nevada in Reno, US, praised the "good work" by the research team. But he said it was plausible that natural processes could have caused some stone tools to migrate downwards in the clay - giving the impression of a pre-Clovis layer.
     Waters has been working at the site since 2006, and analysis of the artifacts collected from the site is ongoing. Waters says, "These studies will help us figure out where these people came from, how they adapted to the new environments they encountered, and understand the origins of later groups like Clovis."

Edited from EurekAlert!, BBC News, VOA News (24 March 2011), AZ Central (25 March 2011), Irish Examiner (26 March 2011)