Anglerphobe wrote:Okay, a serious one now. Why does South America have an abundance of monkeys while North America is almost entirely monkey-free? I really can't wrap my head around it. The continents of Africa and South America separated far too long ago for them to simply be the two divergent halves of an existing population, and I can conceive of no feasible way that a monkey could reach the new world from the old.
The current thinking is that monkeys reached South America from Africa via rafting when the continents were still relatively close together. Old World monkeys form a monophyletic clade and are more closely related to apes than to New World monkeys, meaning you're more closely related to a baboon than a baboon is to a capuchin.
As for why South America has monkeys but North America doesn't, that relates to the broader question of why North American animals were much more successful at colonizing South America than South American animals were at colonizing North America during the Great American Interchange (the two most notable examples of the latter are the opossum and the armadillo, both of which are remarkably versatile creatures). There are usually two main reasons given for this:
- Most of South America is tropical but only a small portion of North America is. North American animals were able to cover most of South America without adapting to temperate climates, while South American animals had access to tropical climates only as far as southern Mexico.
- North American animals had to compete with the best of Eurasia and Africa (well, the best temperate-adapted animals) via the Bering Straight land bridge, while South America had been an island, meaning South American animals only had to compete with animals that arrived via rafting until a land bridge with North America was formed.
Interestingly, one exception to the pattern of North American species being more successful is found in the Caribbean, which is of course a collection of Islands making it necessary for species to arrive via rafting. Prevailing winds favor South American fauna (especially birds) and some South American species have been introduced to the tip of Florida (also tropical) without having to go the long away around. I wasn't aware of any native monkey species native to the Caribbean, so I looked it up, and monkeys made it as far as Cuba, but then were mostly killed off by the Indians and finished off by the Spanish.