is thought to have been caused by the extinction of the megaherbivore prey upon which they depended. The cause of the extinction of the megafauna is debated but has been attributed to the impact of climatic change, competition with other species including overexploitation by newly arrived human hunters, or a combination of both. One study proposes that several extinction models should be investigated because so little is known about the biogeography of the dire wolf and its potential competitors and prey, nor how all these species interacted and responded to the environmental changes that occurred at the time of extinction. Ancient DNA and radiocarbon data indicate that local genetic populations were replaced by others within the same species or by others within the same genus. Both the dire wolf and the Beringian wolf went extinct in North America, leaving only the less carnivorous and more gracile form of the wolf to thrive, which may have outcompeted the dire wolf. One study proposes an early origin of the dire wolf lineage in the Americas which led to its reproductive isolation, such that when coyotes, dholes, gray wolves, and Xenocyon expanded into North America from Eurasia in the Late Pleistocene there could be no admixture with the dire wolf. Gray wolves and coyotes may have survived due to their ability to hybridize with other canids – such as the domestic dog – to acquire traits that resist diseases brought by taxa arriving from Eurasia. Reproductive isolation may have prevented the dire wolf from acquiring these traits. Dire wolf remains having the youngest geological ages are dated at 9,440YBP at Brynjulfson Cave, Boone County, Missouri, 9,860YBP at Rancho La Brea, California, and 10,690YBP at La Mirada, California. Dire wolf remains have been radiocarbon dated to 8,200YBP from Whitewater Draw in Arizona, However, one author has stated that radiocarbon dating of bone carbonate is unreliable. See also Beringian wolf Pleistocene wolf List of North American animals extinct in the Holocene Notes References Works cited External links For younger readers – Dire Wolf by Marc Zabludoff, Marshall Cavendish, 2009 The Evansville Dire Wolf Information on the dire wolf from the Illinois State Museum Canina (subtribe) Prehistoric canines Pleistocene carnivorans Holocene extinctions Pleistocene first appearances Pleistocene mammals of North America Pleistocene mammals of South America Pleistocene mammals of Asia Fossil taxa described in 1858 Mammals described in 1858 Apex predators