Ancient DNA reveals late survival of mammoth and horse in interior Alaska

Abstract

Causes of late Quaternary extinctions of large mammals (''megafauna'') continue to be debated, especially for continental losses, because spatial and temporal patterns of extinction are poorly known. Accurate latest appearance dates (LADs) for such taxa are critical for interpreting the process of extinction. The extinction of woolly mammoth and horse in northwestern North America is currently placed at 15,000 -13,000 calendar years before present (yr BP), based on LADs from dating surveys of macrofossils (bones and teeth). Advantages of using macrofossils to estimate when a species became extinct are offset, however, by the improbability of finding and dating the remains of the last-surviving members of populations that were restricted in numbers or confined to refugia. Here we report an alternative approach to detect 'ghost ranges' of dwindling populations, based on recovery of ancient DNA from perennially frozen and securely dated sediments (sedaDNA). In such contexts, sedaDNA can reveal the molecular presence of species that appear absent in the macrofossil record. We show that woolly mammoth and horse persisted in interior Alaska until at least 10,500 yr BP, several thousands of years later than indicated from macrofossil surveys. These results contradict claims that Holocene survival of mammoths in Beringia was restricted to ecologically isolated high-latitude islands. More importantly, our finding that mammoth and horse overlapped with humans for several millennia in the region where people initially entered the Americas challenges theories that megafaunal extinction occurred within centuries of human arrival or were due to an extraterrestrial impact in the late Pleistocene.extinction ͉ permafrost ͉ megafauna ͉ Beringia

Applications of next generation sequencing in molecular ecology of non-model organisms

“…The sequence information is then used to identify the species present in the sample (Valentini et al, 2009). Studies using this approach have, for example, investigated the diet of a variety of animals by sequencing faecal samples (Deagle et al, 2009), and characterized the extinct mammalian fauna using ancient DNA from frozen tundra sediment (Haile et al, 2009). NGS barcoding approaches have also been extensively utilized to study meta-genomics of micro organism communities (Alvarez et al, 2009;Buée et al, 2009;Andersson et al, 2010).…”

Long livestock farming history and human landscape shaping revealed by lake sediment DNA

“…Recent developments in the combined use of high-throughput sequencing 14 and metabarcoding approaches enable the assessment of the biodiversity of current ecosystems using extracellular DNA that is contained in environmental samples 15,16 . DNA from a variety of taxa, including faecal bacteria, plants and domestic mammals, has been successfully extracted and sequenced directly from natural archives (frozen soils, cave sediments and lake sediments), even in the absence of visible macrofossils [17][18][19][20][21][22][23][24][25] . The application of DNA metabarcoding to lake sediments has also proven its potential to trace past vegetation cover 22 .…”

Timing and causes of mid-Holocene mammoth extinction on St. Paul Island, Alaska

“…Proposed extinction drivers include environmental change, human impacts, or some combination, with the relative contributions of these varying by species and region (2). Woolly mammoths, an iconic Ice Age species, vanished from mainland Asia and North America between 14,000 and 13,200 y ago, with some mainland populations perhaps persisting until approximately 10,500 y ago (1,3,4); however, relict populations survived on two newly formed Beringian islands into the middle Holocene (4-7) (Fig. 1A).…”