Modern primates are very largely confined to tropical and subtropical regions of the world, hence occurring predominantly in the southern continents. The smaller-
The lorises and bushbabies are an Afro-
The Old World monkeys, like the lorises, are an Afro-
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 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-