A string of caves in rural Oregon are now federally protected after being added to the National Register of Historic Places.

Paisley Five Mile Point Caves were listed in recognition of the site's historical and archaeological significance. The caves are already located on federally owned land managed by the Bureau of Land Management.

"BLM is indeed pleased to see the Paisley Five Mile Points officially listed in the National Register of Historic Places," Stan McDonald, a regional archaeologist with the Bureau of Land Management, said in a press release.

"The site's listing underscores the importance of Oregon's archaeological heritage to understanding the full breadth of the human experience."

Ongoing research at the caves has brought about a number of important discoveries in recent years that have changed previously-held beliefs on the earliest colonization of the Americas. Archaeologists have long posited that all indigenous Americans descended from the Paleo-Indian culture known as Clovis culture -- characterized by heavy, leaf-shaped stone spearheads found scattered at ancient settlement sites throughout Central and North America. The Clovis culture and its projectile-point artifacts date to roughly 11,500 to 11,000 years ago.

But evidence at the Paisley Caves -- including stemmed projectile points, grinding stones, manipulated animal bone and braided plant fiber -- suggests a distinct human culture had established itself by the end of the last Ice Age, more than 1,000 years before the Clovis culture. Archaeologists have also found more than 200 examples of human excrement radiocarbon dated to pre-Clovis times. At 14,300 years old, the feces suggest the newly protected heritage site is the earliest example of human habitation in North America.

Ongoing work at the site by a team researchers is being lead by Dr. Dennis Jenkins, an archaeologist at the University of Oregon and a research associate with the school's Museum of Natural and Cultural History. Jenkins's work at the site began in 2002, but archaeologists first began exploring the caves as early as 1938.

"Archaeologists have worked at the site since 1938," said Jenkins. "As we have used increasingly sophisticated scientific techniques in recent years, our understanding of the cultural and megafaunal remains at the site has grown dramatically. Analyses by our research team provides significant new information regarding the timing and spread of the first settlers in the Americas."