New World Monkey origins

[juju]

Hey all! I thought I'd relate to you folks something I was telling a few Cellarites in chat the other day.

Today, there are monkeys living in Africa, Asia, and South America. Species that were ancestral to monkeys, however, are NOT found in any of the fossil deposits in South America. This is because South America was an island continent for most of the Cenozoic era (65 million years ago to present). This means that at some point in time, monkeys, who had been evolving in Africa for quite some time, just magically appeared in South America.

In the Eocene (37 - 53 million years ago), which is about the time anthropologists think monkeys arrived in South America, the earth looked like this:



This geography presents a problem to anthropologists. Since South America was an island when monkeys first appeared there, how in the bloody hell did they get there??

The current working theory is that they rafted there from Africa on floating masses of vegetation.

Apparentely, huge chunks of vegetation actually do break off now and then and just float away. I don't know much about this, except that I'm told it's been documented to happen, and still happens today.

If monkeys did raft to South America, they could have come from three places: North America, Africa, or Asia (through Antartica). Most anthropologists seem to think an African origin is most likely, based on the similarities of certain fossils. The ancient water currents would also have been favorable for an African origin.

They could have also traveled from North America via Island-hopping. Lots of people seem to also be for this origin, but it seems unlikely because A) rafts of vegetation don't form on small islands, and B) the species in North America that NWMs would have evolved from are much farther down the evolutionary tree than the potential African ancestors.

Another suggestion is that they came from Asia, rafted across to Antartica, and traveled via a land connection to South America. But since no primate ancestors have been discovered in Antartica, not many people are for this idea.

When I told Whit and Slang about this, Slang asked about travel times. That's answered in this paper, which has the following chart:



The linked PDF argues for an Antartic route, and it goes into much more depth about this stuff. So it's worth checking out if you're interested. Anyway, that's all I'll say on that for now. It's really fucked up, sounds compeletely ridiculous, and is only the current working theory because there are no other ideas.

edit:

According to the linked articlle, this theory is also used to explain to origins of South American acridian insects, West Indian Coleoptera, Lake Malawi fishes, many shallow-water animals, some amphibians and reptiles including Crocodilia, Crotalus rattlesnakes of Baja California, land reptiles of Western Samoa, South American indigenous gekkos, some land vertebrates of the Krakatau Islands, land mammals of the Mediterranean islands, South American caviomorph rodents, a group of Australian rodents, and possibly a group of South American sloths.