Thursday, March 24, 2011

Earliest American residents came at least 15,500 years ago


New discoveries at a Central Texas archaeological site by a Texas A&M University-led research team prove that people lived in the region far earlier – as much as 2,500 years earlier – than previously believed, rewriting what anthropologists know about when the first inhabitants arrived in North America. That pushes the arrival date back to about 15,500 years ago.

Michael Waters, director of Texas A&M's Center for the Study of First Americans, along with researchers from Baylor University, the University of Illinois-Chicago, the University of Minnesota, and Texas State University, have found the oldest archaeological evidence for human occupation in Texas and North America at the Debra L.Friedkin site, located about 40 miles northwest of Austin. Their work is published in the current issue of Science magazine.

Waters says that buried in deposits next to a small spring-fed stream is a record of human occupation spanning the last 15,500 years. Near the surface is the record of the Late Prehistoric and Archaic occupants of the region. Buried deeper in the soil are layers with Folsom and Clovis occupations going back 12,000 to 13,000 years ago.

"But the kicker was the discovery of nearly 16,000 artifacts below the Clovis horizon that dated to 15,500 years ago," Waters notes.

"Most of these are chipping debris from the making and resharpening of tools, but over 50 are tools. There are bifacial artifacts that tell us they were making projectile points and knives at the site," Waters says. There are expediently made tools and blades that were used for cutting and scraping."

Multiple studies have shown that the site is undisturbed and that the artifacts are in place and over 60 "luminescence dates" show that early people arrived at the site by 15,500 years ago, Waters explains. Luminescence dating technique is a method used to date the sediment surrounding the artifacts. It dates the last time the sediment was exposed to sunlight.

For more than 80 years, it has been argued that the Clovis people were the first to enter the Americas, Waters says. He goes on to say that over the last few decades, there have been several credible sites which date older than Clovis found in North America -- specifically in Wisconsin, Pennsylvania, Florida, and Oregon.

"However, this evidence is not very robust," Waters observes.

"What is special about the Debra L. Friedkin 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.

"This discovery challenges us to re-think the early colonization of the Americas. There's no doubt these tools and weapons are human-made and they date to about 15,500 years ago, making them the oldest artifacts found both in Texas and North America."

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

The Clovis people, whose tools were known for their distinctive "fluted" points, were once thought to be the original settlers of North America about 13,000 years ago. Over the past few years, however, scattered evidence has hinted at several earlier cultures. But, such evidence has often been disputed in part because so few artifacts have actually been recovered.

These are some of the artifacts from the 15,500-year-old horizon.

The newly discovered tools are small and made of chert, and the researchers suggest that they were designed for a mobile toolkit—something that could be easily packed up and moved to a new location. These tools are recognizably different from Clovis tools although they do share some similarities, including the use of biface and bladelet technology.

UIC earth and environmental sciences professor Steven Forman worked with Waters and a multi-university team of researchers, finding buried beneath the Clovis layer tools such as blades and cores -- technologies unique to the Clovis culture.

Forman gathered about 50 core samples from two sites at Buttermilk Creek for luminescence dating analysis at UIC. Carbon-14 dating couldn't be used to date the pre-Clovis artifact layer because that layer didn't contain any organic matter.

"We dated the sediments by a variety of optical methods," Forman said. "We also dated different mineral fractions as well, and we consistently got the same ages. We looked at the age structure of the sediment by many different ways and got the same answers."

This is the first time that optical dating has been used to constrain a paleoculture within a date range, Forman said.

Luminescence dating, a relatively new technique, measures light energy trapped in minerals such as feldspar and quartz formed centuries ago. Samples must be carefully handled to avoid any exposure to light, which would contaminate the readings. They were analyzed in a darkroom laboratory at UIC.

In the past, researchers have argued that the Clovis people were the oldest human inhabitants of the Americas. This "Clovis First" model theorizes that the Clovis people came to the New World from Northeast Asia by crossing the Bering Land Bridge, which once connected Asia and North America. From there, it suggests that they spread out across the continent and eventually made their way down to South America.

However, some problems with this model have recently arisen. First of all, no Clovis technology has been found in Northeast Asia and the fluted points that have been discovered in Alaska are all too young to be Clovis. (They were also made a bit differently than Clovis points.) Furthermore, there are six sites in South America that do not contain Clovis technology, although they did exist during the same time period.

The Debra L. Friedkin site in Texas, implies that Clovis tools could have eventually evolved from the tools found in the Buttermilk Creek Complex—and that the Clovis culture, including the use of fluted points, likely developed in North America.

"This discovery provides ample time for Clovis to develop," said Waters. "People [from the Buttermilk Creek Complex] could have experimented with stone and invented the weapons and tools that we now recognize as Clovis… In short, it is now time to abandon once and for all the 'Clovis First' model and develop a new model for the peopling of the Americas."

No comments: