GEOSPATIAL ANALYSIS OF HUMAN-MEGAFAUNAL OVERLAP IN NORTH AMERICA

The role of humans in the disappearance of megafauna during the late Pleistocene extinction is a source of ongoing debate, particularly important in light of humanity’s role in the ongoing Anthropocene extinction. Few sites preserve physical evidence of human-megafaunal coexistence, making trends difficult to detect even with geographic proximity and overlapping radiocarbon-dated ages. Where overlap does occur, as in the Paisley Caves or Manis sites, it is difficult to determine whether these were remnant local populations that interacted with paleoindians or whether humans were drivers behind extinction. To address the problematic lack of explicit overlap, we used kriging interpolation methods on 378 calibrated radiocarbon dates to examine local and continental trends in the overlap between megafaunal last occurrence and human first appearance dates.

Though humans occupied most of North America before the megafaunal extinction, the highly localized patterns of our overlap models lend little support to either the Blitzkrieg or illness theory of extinction; no continent-wide trend exists. Human and megafaunal overlap is regional in nature, and varies between human arrival post-dating local extinction by several hundred years (Alaska, Great Plains) to pre-dating it by over a thousand years (Midwest). Our models also predict a significantly younger extinction event than previously estimated; barring singleton survivor dates, the bulk of megafaunal last occurrences took place between 10,700 and 11,300 years BP. Considering model uncertainty, several older extinction events may be more related to the Younger Dryas than to human occupation. Older extinctions were also primarily on northern coastlines that were not covered by the Laurentide Ice sheet. These areas may have been more prone to extreme weather caused by ice cap melting during the Younger Dryas, causing regional droughts or fires that may have precipitated local population collapse.