Instead of comparing the effect of environment as a whole on different peoples, we can also isolate its single factors, such as the presence of particular species of plants or animals. One of the strongest cases against the creative influence of environment on culture lies in the phenomena relating to the domestication of animals in the Old and the New World. The one animal domesticated in both hemispheres is the dog, which occurs in Neolithic Europe and is also found with archæological remains in America. But while in the Old World there is in addition an imposing series of species subjected to man for definite economic utilization, it is only in Peru that the American natives entered into a symbiotic arrangement with other animals, _viz._, the llama and the alpaca. Why was not the bison of the great Plains tamed like the buffalo of southern Asia or the various races of cattle in the Eastern Hemisphere? No valid reason can be advanced on geographical grounds. More striking still in this regard is the difference between the hyperborean populations of Asia and North America. The Chukchee of north-easternmost Siberia and the Eskimo share the same climatic conditions and their territories are both inhabited by the reindeer (caribou). Yet the Chukchee breed half-tamed reindeer on a large scale, using the animals for food and draught with sledges, while no attempt in this direction was made by the Eskimo or any of their Indian neighbors. The same external condition fails to produce the same cultural result. But even among the Chukchee there is evidence that the use of reindeer did not take place in response to an environmental stimulus. It appears that the extraordinary development of reindeer breeding is a relatively new thing with the Chukchee, who were formerly hunters of sea-mammals like the Eskimo. Before the recent efflorescence of their reindeer culture, the Chukchee waged war on their southern neighbors, the Koryak, for the purpose of carrying off their herds; and altogether it seems that both Chukchee and Koryak adopted the idea of taming the reindeer from tribes of the Tungus stock living to the west and south.[3] We are, then, dealing with another instance of acculturation due to contact.