Thousands of artifacts from a site in Central Texas, including a dozen projectile points, have provided researchers with new clues about the arrival and spread of First Americans on the continent. The items, which are up to 15,500 years old, hint that the Americas may have been populated in multiple waves of migration via different routes.
In the long-simmering debate over when and how humans arrived in the Americas, there are few things researchers can agree on. Paleogenetic studies have confirmed the First Americans arrived from Asia, but the timing, the route and how they spread across the continents remain contested.
Archaeologists have looked for answers in the stone tools these early explorers left behind, but even there, definitive evidence is scant.
For years, based on artifacts found mostly in North America, the conventional thinking was that humans crossed Beringia — the now-submerged land bridge that once linked Siberia and Alaska — as glaciers receded, and developed a distinct tool-making style, called Clovis, that spread across the continent around 13,000 years ago.
That old school view of the First Americans has taken a beating in recent decades, however, as new sites emerge and paleogenetic data improves.
It now appears that people were in the Americas at least 16,000 years ago and possibly much earlier, well before an overland route opened between the glaciers. Enter the Kelp Highway, a more recent model suggesting that humans arrived in the Americas from Asia via resource-rich coastlines. The Kelp Highway hypothesis is emerging as the most likely earliest migration route for the First Americans — but not the only one.
In lieu of human remains, the best way to glean how people first moved across the Americas is through the tools they left behind, particularly projectile points such as spear tips and arrowheads, which bear stylistic signatures of their makers.
The Clovis culture, for example, is known for projectiles that had a distinctive fluted depression, among other traits. Western Stemmed points, however, are narrower, lack the Clovis fluting and were made using a different shaping technique. This style of projectile point is found throughout the western U.S. and, once thought to be younger than Clovis, now appears to be about the same age or even older.
Researchers have long sought to understand how these techniques evolved, and whether they reflect regional traditions or multiple waves of migration and dispersal.
The Texas Two-Step
Reporting today in Science Advances, researchers analyzed a portion of the 100,000 artifacts recovered north of Austin at a location known as the Debra L. Friedkin site. The site is part of an archaeologically rich area, along Buttermilk Creek, that has been excavated for decades. In July, for example, a separate team announced that projectile points at the nearby Gault site, less than a thousand feet upstream from Friedkin, were at least 16,000 years old and possibly 20,000 years old.
The team behind today’s paper focused on dating and analyzing the style of various tools from the Friedkin site, including 12 whole or partial projectile points. Using optically-stimulated luminescence, a dating methodthat reveals when certain types of rock were last exposed to sunlight, the team determined that the sediments in which the artifacts were deposited were 13,500-15,500 years old.
That’s younger than the Gault site finds, but definitely pre-Clovis.
But it’s the styles of the projectiles that’s arguably the most interesting aspect of the study. And yes, “styles” plural. Projectile points made in a variation on the stemmed technique were found throughout sediment layers of different ages. Dating to about 14,000 years ago, however, a new style of point shows up: the triangular lanceolate.
Complete and partial projectile points from the Friedkin site include a triangular lanceolate shape (A) dated to 14,000 years ago. (Credit: Waters et al 2018)
Based on often subtle variations between the artifacts found at the Friedkin site — which, in addition to projectile points included hand axes and other stone tools — the researchers suggest two different hypotheses.
It’s possible, for example, that the tool technology present was in the process of evolving into Clovis — the triangular lanceolate form could be evidence that toolmakers were innovating and refining new methods and shapes.
It’s also possible, however, that the different styles present point to multiple waves of migration into and across the Americas. Stemmed projectiles and their variations may have been the work of one or more early waves of humans traveling along the Pacific coast before moving inland. Clovis, on the other hand, could represent a later population migrating overland from Beringia after the glaciers had receded.
One thing is certain: Archaeologists need to unearth more points from more sites before we can read the first chapter of human history in the Americas.