Modern primates are very largely confined to tropical and subtropical regions of the world, hence occurring predominantly in the southern continents. The smaller-bodied prosimian primates are even more restricted in their distribution, while a few of the larger-bodied higher primates (notably macaques) can occur quite far north in regions where snow is found in winter (Barbary, rhesus, and Japanese macaques). The lemurs are confined to Madagascar and are the only primates to occur on that island. The lorises and bushbabies are an Afro-Asian group. However, whereas the lorises occur in both Africa and Asia, the bushbabies occur only in Africa. The tarsiers are restricted to various islands in Southeast Asia. The New World monkeys occur in South and Central America and are the only primates to be found in the Neotropical region. The Old World monkeys, like the lorises, are an Afro-Asian group with a very wide distribution. However, the guenons and their relatives primarily occur in Africa, with only the macaques as an essentially Asian offshoot, while the leaf-monkeys are primarily Asiatic and represented in Africa only by the colobus monkeys. Finally,

Golden snub-nosed monkeys (Pygathrix roxellana) are found along the Tibetan Plateau in China. (Photo by Christian Grzimek/OKAPIA/Photo Researchers, Inc. Reproduced by permssion.)

the hominoids are also an essentially Afro-Asian group, although humans began to expand outside that range about two million years ago. The gibbons and the orangutan are found only in Southeast Asia, while chimpanzees and gorillas are confined to Africa.

In the distant past, during the Eocene epoch, primates occurred at very high latitudes in North America and Europe, in regions where they subsequently left no trace. One plausible explanation for this is that a marked increase in ambient temperatures at higher latitudes that marked the transition from the Paleocene to the Eocene led to a northward expansion of tropical and subtropical forests, thus expanding the potential geographical range of habitats available to primates. At the end of the Eocene, temperatures at higher latitudes declined markedly and this doubtless explains why primates virtually disappeared from the northern continents at that time, with only a few species surviving for a while into the Oligocene. In fact, it seems likely that primates also occurred widely in the southern continents during the Eocene, at least in Africa and Asia, but for various reasons we have very few fossils from those regions. The most likely interpretation for

An olive baboon (Papio hamadryas anubis) devours a freshly killed baby antelope. (Photo by Peter Davey. Bruce Coleman, Inc. Reproduced by permission.)

the current geographical distribution of primates is that they have always been present in the south and that their range expanded temporarily into the north during the Eocene when temperatures where higher, only to contract again at the end of the Eocene when temperatures declined. In the Old World, primates also occurred somewhat further to the north during the Miocene, as fossil apes and monkeys from that epoch have been documented for the circum-Mediterranean region, for southern Europe and as far north as Hungary and Czechoslovakia.

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