Climate change kicked into high gear during the Pleistocene epoch, whose alternating cold, dry ice ages and warm, humid intervals was a tumultuous time for all animal and plant evolution. Many mammal species on the northern continents (North America and Eurasia), particularly herbivores, attained giant sizes as an adaptation to extreme cold. Large body size helped not only to conserve heat, but also to store more fat to cope with winter weather. Woolly mammoths, giant deer, and woolly rhinos roamed Eurasia, and the woolly mammoth, mastodon, giant ground sloth, large saber-tooth cat, and dire wolf reigned supreme in North America. Most such megafauna became extinct at the end of the Pleistocene, about 10,000 years ago. But the gray wolf, Canis lupus, is one of the few exceptions, and remains one of the most successful large canids in the world.
From about the beginning of the Pleistocene the genus Canis has had a continuous presence in Eurasia, along with various species of fox and raccoon dog. Gray wolves are present beginning about 1 million years ago. Early humans—Homo erectus, H. neanderthalensis, and H. sapiens—must have competed with some larger species of canids, because they shared a broadly similar hunting (and scavenging) lifestyle. By the end of the Pleistocene, the inevitable close encounters between modern humans and wolves—in the Middle East or Europe, or possibly China—resulted in the first domestication of a canid. If one counts the domestic dog as a highly specialized adaptation for cohabiting with humans, then canids have achieved ultimate success in occupying nearly every corner of the world—in all sizes, shapes, and speeds.
This article was adapted from Dogs: Their Fossil Relatives and Evolutionary History, by Xiaoming Wang and Richard H. Tedford and illustrated by Mauricio Antón, © 2008 Columbia University Press. Used by arrangement with Columbia University Press. All rights reserved. Click here for ordering information.
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