Horses have been an important and influential part of North American
             and European history. In his book, Ecological Imperialism: The Biological
             Expansion of Europe, Alfred W. Crosby argues that horses helped to bring
             about European's successful colonization of a number of temperate regions
             such as North America, Australia, New Zealand, and some parts of South
             America. He argues that the profound success of horses in these regions
             resulted from the filling of an empty biological niche, and that the
             arrival of horses on the plains in North America resulted in profound
             changes in the lives of North American Indians. In his article, The Rise
             and Fall of Plains Indian Horse Cultures, Pekka Hãmãlãinen argues that the
             common view that horses brought success to Native Americans is
             fundamentally oversimplified. He suggests that the common focus on only
             the successful incorporation of horses by the Lakota people has distorted
             modern understanding of plains history, and obscures the damaging impact of
             the arrival of horses on native American culture and ecology.
             In Ecological Imperialism: The Biological Expansion of Europe, Crosby
             argues biology played a large part in the fact that Europeans displaced the
             native people of many temperate zones in the world (including North
             America, New Zealand, temperate South America and Australia). While the
             success of European imperialism is commonly thought to stem from military
             might, and advanced technologies, it can be better explained by other
             factors, notes Crosby. Essentially, Crosby argues that the native biology
             of these conquered temperate places (including humans) was not equipped to
             deal with European invaders. European diseases like smallpox decimated
             native populations, and European weeds and agriculture brought large scale
             Overall, the animals, weeds, and diseases that Europeans brought to
             the New Wor...