Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago, Parts 1 and 2: A Discussion

Wolbach et al. published two papers on the Younger Dryas Impact Hypothesis (YDIH)—the paleoenvironmental effects of a purported cosmic impact at the beginning of the Younger Dryas Chronozone (YDC). Part 1 includes a selective summary of previous discussions of the YDIH but leaves out key reviews, uncritically accepts previous interpretations of purported impact, and fails to take into account abundant criticisms and contradictory data. A discussion of ice-core evidence focuses only on the beginning of the YDC rather than on a longer interval that would allow the context of claimed impact indicators to be evaluated. The exceptionalism claimed for many of the key data points is the result of exaggerations, and the graphical analyses themselves are not reproducible. Part 2 presents data from sedimentary records. The authors assume that impacts triggered widespread fires, but the evidence for such a link between extraterrestrial impacts and wildfires is weak. The presence of charcoal at the beginning of the YDC (YDB) fails to unambiguously support the hypothesis of impact-related fires because there is also a large peak at the end of the YDC. Stratigraphic markers used to argue for widespread burning, such as the Usselo soil of northwest Europe and the black mat of the southwestern United States, were shown by their original investigators to have no plausible link to an impact event. Human population decline in North America is not supported by abundant published archaeological, geochronological, and stratigraphic evidence. Late Pleistocene megafauna extinctions varied in time for individual species across the Americas, Europe, and Asia and thus cannot be accounted for by a single impact. If there was some sort of extraterrestrial YDB-age event, it apparently had negligible terrestrial impact.