. You can see in Figure 34.42 that monkeys do not from a clade but rather consist of two grouos, the New and Old World monkeys. Both of these groups are thought to have originated in Africa or Asia. The fossil record indicates that New World monkeys first colonised south America roughly 25 million years ago. By that time, south America and Africa had drifted apart, and monkeys may have reached south America from Africa by rafting on logs or other debris. What is certain is that New World monkeys and Old World monkeys underwent separate adaptive radiations during their many millions of years of separation (Figure 34.43). All species of New World monkeys are arboreal, whereas Old World monkeys include ground-dwelling as well as arboreal species. Most monkeys in both groups are diurnal (active during the day) and usually live in bands held together by social behavior.