The first Americans may not be who we thought they were.

One of the 15,000 year old spear points discovered in Texas. Center for the Study of the First Americans, Texas A&M University

Researchers in Texas have discovered what they believe are spear points used by human hunters some 15,500 years ago, making them the oldest weapons ever found in North America.

The newly discovered spear points pre-date the earliest known weapons made by the Clovis people, whom archaeologists have long believed were the first humans to settle the Americas some 13,000 years ago.

The team of researchers from Texas A&M, Baylor University and the University of Texas made the find at an archaeological site around 40 miles northwest of Austin called the Debra L. Friedkin site, after the family that owns the land. Excavations at the site have been ongoing for more than a decade.

Excavations at the Debra L. Friedkin site in 2016. Center for the Study of the First Americans, Texas A&M University

Researchers uncovered numerous spear points made of chert, a type of rock, as well as other tools, buried in layers of sediment that dating revealed was at least 15,500 years old. Unlike the distinctive spear-shaped stone weapons known as “Clovis points,” which have been found in Texas as well as other parts of the United States and northern Mexico and date to between 12,700 and 13,000 years ago, these older “western stemmed” spear points are smaller, without the distinctive Clovis grooves.

“The discovery is significant because almost all pre-Clovis sites have stone tools, but spear points have yet to be found,” Michael Waters, a professor of anthropology at Texas A&M, said in a statement. “The dream has always been to find diagnostic artifacts—such as projectile points—that can be recognized as older than Clovis, and this is what we have at the Friedkin site.”

Waters and his team believe the earliest Americans used these spear points to hunt mammoths and the other large animals that roamed what is now Central Texas more than 15,000 years ago. Their findings, published in the journal Science Advances, may force scientists to rethink the accepted wisdom about human settlement in North America—yet again.

A Stemmed Lanceolate projectile point that dates about 15,000 years old. Center for the Study of the First Americans, Texas A&M University

Archaeologists long believed the first humans to settle in the Americas did so around 13,000 years ago, by walking from Alaska through an ice-free corridor in western Canada before heading southward. But the discovery of the Monte Verde settlement in southern Chile, which dates back at least 14,500 years, poked holes in that theory, as at that time the ice-free route through Canada didn’t exist.

The new discovery of Texas may also help rewrite the long-accepted timeline, and offer potential support for the theory that the earliest Americans may have arrived not by land but by sea, entering at various points along the Pacific Coast.

“The findings expand our understanding of the earliest people to explore and settle North America,” Waters said. “The peopling of the Americas during the end of the last Ice Age was a complex process and this complexity is seen in their genetic record. Now we are starting to see this complexity mirrored in the archaeological record.”