FORT WORTH, Texas – Archaeologists at a Central Texas site have unearthed artifacts that the first humans arrived in North America roughly 2,500 years earlier than previously thought, raising questions about how they made it to the New World and what route they took to get here.

The artifacts found near Salado by a Texas A&M University-led team date back as far as 15,500 years, more than 2,000 years before the Clovis people who were long believed to be the first humans in North America. The so-called Clovis people, known for their unique spearhead artifacts, were named after a site found in 1930 near Clovis, N.M.

The numerous Clovis artifacts were found over the last 80 years and showed the Clovis people lived as far back as 13,100 years ago.

The Salado site isn’t the first find to challenge when humans migrated to the Americas — other sites have been found in Pennsylvania, Oregon and Chile — but it is the most complete with over 16,000 artifacts, said Michael Waters, director of the Center for the Study of the First Americans at Texas A&M University.

Most of the items would look like crude spears, knives, notches or other types of cutting or sharpening tools. But they indicate the area along a spring-fed creek was used as a campsite as they came and went from the area.

The evidence shows human occupation almost continuously for 15,000 years and signs that water was present even during times of drought.

If humans arrived 2,500 years earlier in North America, it also raises the question of how they made their way to Texas.

Fifteen thousand years ago, the Canadian ice sheets would have blocked a land migration to North America, Waters said. That theory espoused by Waters and other archaeologists raises the possibility that humans traveled by boat along the West Coast of what is now Canada down to the Columbia River along the present-day Washington-Oregon border — or perhaps even farther south.

“If you look at the genetic evidence, the native people in North America came from Northeast Asia, then crossed over into the New World, either coming across by the Bering land bridge or they could have skirted over by boat,” Waters said. “The corridor between the two ice sheets was closed 15,000 years ago. The only option to them is to come by boat in this kind of secondary way, along a coastal route to get into North America.”

Besides Baylor and Texas A&M, the work included researchers from the University of Illinois-Chicago, the University of Minnesota and Texas State University. Their findings were released Thursday and are being published in the current issue of Science magazine.