Estimates of the number of Native Americans living in what is now the United States at the onset of European colonization range from two to 18 million, with most historians tending to ward the lower figure. What is certain is the devastating effect that European disases had on the native population practically from the time of initial contact. Smallpox, in particular, destroyed whole communities and thought to have been a much more direct cause of the steep decline in Indian population in the 1600s than the numerous wars with European settlers.