For years, archaeologists have argued over when humans first settled South America. Now, a collection of artifacts discovered in southern Chile has re-ignited the debate, the Christian Science Monitor reports.

In the 1970s, archaeologist Tom Dillehay discovered evidence indicating that people had lived in the region’s Monte Verde site as far back as 15,000 years ago. His findings challenged researchers’ assumptions that the Clovis, large-game hunters, were the first group to settle the area—2000 years later. 

Later digs indicated that the Clovis weren’t Monte Verde’s progenitors. Now, Dillehay is moving the timeline back even further, reporting that subsequent investigations in 2013 revealed stone tools, fire pits, burnt animal bones, and edible plants that were between 14,500 and 18,500 years old. His findings, which were published in the journal PLOS ONE, suggest the region's ancient civilizations may have been even more advanced and nomadic than archaeologists previously realized. (Some of the tools discovered are made from non-native limestone and white quartz, indicating that they were transported to southern Chile from another area.)

Serpentine pebble tool from Monte Verde showing bifacially knapped and retouched edge. Serpentine is a raw material available in the coastal cordillera west of Monte Verde. Researchers suggest these were made by human hands. Others aren't so sure. Image credit: Dillehay et al. in PLOS ONE

According to Science, Dillehay's updated timeline means the ancient people who left Siberia 23,000 years ago may have reached the Americas in less time than researchers had thought. Since the Ice Age was just ending, they may have also hunted for game throughout de-glaciated stretches of land between Chile’s coast and the Andes.

Some archaeologists are skeptical about Dillehay’s announcement, questioning whether humans actually made the stone relics and fire pits. They also point to the fact that there still is no evidence of humans occupying North America before 14,300 years ago. Even so, it goes to show that there will always be new findings that serve to shake up our understanding of when—and how—humans started calling the Americas home.

[h/t Christian Science Monitor, Science]