�鶹��Ժ

Radiocarbon dating of artifacts and bones shows North American Indigenous population changes over 2,000 years

A small team of archaeologists and anthropologists from the University of Wyoming, Michigan State University, and the Desert Research Institute, all in the U.S., has used radiocarbon dating of bone and other artifacts found at various sites across North America to learn more about Indigenous population fluctuations before the arrival of Europeans.

In their paper in Proceedings of the National Academy of Sciences, the group describes how they used dating of tens of thousands of objects to gain insights into population centers across North America over the past 2,000 years, and what they learned by doing so.

The best of science, now on Instagram! Follow .�ʵ🔬

Over the past several decades, studies have assessed the massive population decline of people indigenous to North America following the arrival of European settlers. But, the researchers on this new effort note that little work has been done to assess population numbers prior to their arrival. In this new effort, the research team sought to fill in some of the gaps by conducting a long-term field study of material left behind by Indigenous people in what is now the United States and Canada.

The work by the team involved obtaining food scraps, charcoal bits, textiles, bones, and other artifacts left behind by Indigenous people over 2,000 years and then carbon dating them. The work took over 10 years—in all, the team collected more than 60,000 radiocarbon dates from the objects.

To make population estimates, the researchers made correlations between the abundance of the objects they dated and their type. They used that to estimate how many people likely lived in a given area over the 2,000-year period. They then used such estimates to develop population numbers for the whole continent over the same period.

Looking at their maps and data, the researchers found that population growth and decline varied over time and area—some areas grew in population while others shrank. For example, the population of Cahokia, the largest known city in prehistoric North America, peaked around 1100 and then declined soon thereafter due to over-farming, hunting and climate change. By 1350, no one was left.

The research team also found that the population of North America reached its maximum by approximately 1150—after that, there were ebbs and flows across the continent. The population was rebounding when the Europeans began arriving, but then began dropping soon thereafter and continued to crash over the following centuries.