Process-explicit models reveal pathway to extinction for woolly mammoth using pattern-oriented validation

Abstract

Processes leading to the megafauna extinctions of the late Pleistocene and early-Holocene are uncertain, with intense debate on the roles of human hunting and climatic change. Using process-explicit simulations of climate-human-woolly mammoth interactions, which integrate spatiotemporal evidence from fossils and ancient DNA, we show that humans accelerated the timing of range collapse, extirpation and eventual extinction of woolly mammoth in Eurasia. Population growth and northward migrations of people during the late Pleistocene led to the premature extirpation of populations of woolly mammoth in areas of Eurasia that were climatically suitable into the Holocene, hastening climate-driven declines by up to 4,000 years in some regions. Our simulations also pinpoint mainland Arctic refugia where mammoths likely persisted until the mid-Holocene, some 5,000 years longer than previously thought. Our results reveal that the role of humans in the extinction dynamics of woolly mammoth was long and chronic, and not limited to a Holocene over-kill.

Process‐explicit models reveal pathway to extinction for woolly mammoth using pattern‐oriented validation

“…Pie charts show variance explained (%) by climate (blue), humans (orange) and area of occupancy at the start of each period (grey). Histograms show contribution to explained variance for magnitude (M) or pace (P) of variables detailed in Appendix 1 of Fordham & Brown (2020). White areas of pie chart represent unexplained variance.…”

“…); maximum population growth rate (Pop growth); and variation in population growth rate (Var growth). See Supporting Information Methods and Appendix 3 in Fordham and Brown (2020) for more details…”

“…To identify and evaluate the processes and drivers that caused the initial population collapse of woolly mammoth, and later the susceptibility of small residual populations to eventual extinction (declining and small population paradigms; Caughley, 1994), we discretised results from the best 900 models into three distinct climatic periods (T1 = 21–15 ka BP, T2 = 15–11 ka BP and T3 = 11–5 ka BP) (Clark et al, 2012) and three sub‐regions (Europe, Asia, Beringia). For each period and region (including all of Eurasia) we computed the magnitude and pace of climatic change, human population growth and expansion (Fordham & Brown, 2020). We calculated expected minimum abundance (EMA) at the termination of each period (T1‐T3) for each region.…”

“…Radiocarbon dated and georeferenced fossils for the woolly mammoth ( M . primigenius ) during the Late Pleistocene and Holocene were sourced from publicly accessible databases and published literature (Fordham & Brown, 2020). Their age reliability was assessed (Barnosky & Lindsey, 2010) and all reliable ages were calibrated using OxCal (Bronk Ramsey, 2009) and the IntCal13 calibration curve (Reimer et al, 2013).…”

Ancient Faunal History Revealed by Interdisciplinary Biomolecular Approaches

“…These climatic oscillations forced species to retreat into and expand from refugial areas, still visible in the genetic diversity and current distribution patterns of extant species [32][33][34]. At the end of the Pleistocene and beginning of the Holocene, the combined impact of these climatic fluctuations [35,36] and human expansion [35,37] disproportionately affected some large mammals, leading to their decline and final extinction (i.e., woolly mammoth, giant deer, woolly rhinoceros, and cave bear) [38]. Below, we will begin by describing two megafaunal species extensively studied from a biomolecular perspective: the cave bear (Ursus spelaeus sensu lato) and the woolly mammoth (Mammuthus primigenius) (Figure 1), from which abundant remains have been retrieved from circumstances particularly favourable for biological preservation, e.g., cave sediments and permafrost.…”