Spatiotemporal distribution of the North American Indigenous population prior to European contact.

We examine spatiotemporal trends in the pre-European-contact Indigenous population of North America using radiocarbon (14C) dates of the past 2000 y. At a continental scale, the Indigenous population of the past ~14,000 y peaked at ~1150 CE and then declined until a brief recovery shortly before 1500 CE, after which 14C probability declines precipitously. After testing, we reject the hypothesis that the 1150 CE peak and decline is a result of 14C sampling issues. We then examine the 14C record of the past 2000 y in each of 18 watersheds where we find peaks ranging from ~800 to 770 CE to after European contact, with the majority, in the interior of the continent, declining ~1080 to 1300 CE. Although all Indigenous populations declined after European contact, that of a large portion of the country (the Great Lakes, New England, the Mid-Atlantic, the Central Plains, the Northwest, and California) did not decline until after contact.