The climate began to change 18,000 years ago, and humans didn?t arrive until about 12,000 years ago. This meant that the changes were still occurring at the time of human arrival, and the animal populations would not yet have had a chance to recover. From the archeological sites containing projectile points together with bones of the megafauna, we know for sure that humans did kill the animals. People may have been the final component in the in extinction of the megafauna, but most likely not the only one. If climate change had not affected the faunal populations, the amount of animals on the continent when early people arrived would have been abundant. It is improbable that man alone could have killed off thirty-five genera of animals in the period of two-thousand years. If climate change had been the only factor in depleting the megafaunal population, survival rates would likely have been high enough to sustain. Therefore, it is highly probable that the changing climate began the diminution of the megafaunal population, but that the process was extenuated by humans.
Elias, Scott A.
1997 The Ice Age History of Southwest National Parks. Washington and London: Smithsonian Institution Press
Fagan, Brian M.
1995 Ancient North America: The Archaeology of a Continent. London: Thames and Hudson Ltd.
Fagan, Brian M.
1987 The Great Journey: The Peopling of Ancient America. London: Thames and Hudson Ltd.
Fiedel, Stuart J.
1987 Prehistory of the Americas. Cambridge: Cambridge University Press.
Grayson, Donald K.
1993 The Desert?s Past: A Natural Prehistory of the Great Basin. Washington and London: Smithsonian Institution Press
Haynes, Gary.
1991 Mammoths, Mastodonts, & Elephants: Biology, Behavior, and the Fossil Record. Cambridge: Cambridge University Press.
Sutcliffe, Antony J.
1985 On the Track of Ice Age Mammals. Cambridge: Harvard University Press
Ward, Peter D.
1997 The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared. New York: Copernicus
Van Couvering, John A.
1997 The Pleistocene Boundary and the Beginning of the Quaternary. Cambridge: Cambridge University Press.