Human Evolution: Convergence or Land Bridge?

There is a book by Boyd and Silk entitled, "How Humans Evolved." In the fourth edition, page 260-261, the authors discuss the emergence of New World primates. The following is a sample of the text:

"The origins of New World primates is a great mystery. It is not clear how monkeys got to South America or how they found their way to the islands of the Caribbean. The absence of Oligocene primate fossils in North America and the many similarities between New World monkeys and the Fayum primates suggest to many scientists that the ancestor of the New World monkeys came from Africa. The problem with this idea is that we don't know how they could have gotten from Africa to South America. By the late Oligocene, the two continents were separated by at least 3000 km (about 2000 miles) of open ocean. Some authors have suggested that primates could have rafted across the sea on islands of floating vegetation. Although there are no well-documented examples of primates rafting such distances, fossil rodents appear in South America about the same time and are so similar to those found in Africa that it seems very likely that rodents managed to raft across the Atlantic.

"Other researchers suggest that New World monkeys are descended from a North American primate. But there are two problems with this hypothesis. One is that, although there is evidence of Eurasian prosimians reaching North America earlier (during the Eocene), there are no known anthropoid fossils from North America- for any time period. If we assume that an early anthropoid reached North America at about the same time, then the extensive similarities between Old World and New World monkeys could be readily explained. Otherwise we would have to reach the improbable conclusion that New World monkeys are descended from a prosimian ancestor, and that the many similarities between New World and Old World monkeys are due to convergence.

"The second difficulty with this hypothesis is geographic. Because North America did not join South America until 5 mya, this scenario also requires the anthropoid ancestor to have made an ocean voyage, though it may have been possible to break up the voyage by hopping across the islands that dotted the Caribbean. Still other possibilities may exist (Figure 10.17).

"The most intriguing hypothesis is that anthropoid primates actually appeared in Africa much earlier, when a transatlantic journey would have been easier to complete. Atlantic sea levels were lowest during the middle of the Oligocene. The Fayum primates with the closest affinities to New World monkeys are considerably younger than this. However, this may not be a fatal liability for the hypothesis. There is good reason to believe that the date of the earliest fossil we have discovered usually underestimates the age of a lineage. The method outlined in Box 10.3 suggests that anthropoids actually originated at least 52 mya.


Considering that there is great uncertainty regarding how anthropoids got to South America, can we ask ourselves if it's possible that a land bridge once existed between Africa and South America? Perhaps a land mass along the mid-Atlantic ridge? Sounds like Atlantis to me...

(For those of you wondering, Fig 10.7 is a picture of a monkey surfing on a surfboard, which is supposed to illustrate and poke fun at the fact that so little is known about this topic.)

reply to post by WashingtonGrewHemp


I definitely believe that some kinda branching took place to form the pacific, atlantic, and arctic race. I remember hearing a theory about this in anthro, 3 major branch offs in primates, forming a Trident?

these NA 'monkeys' had no furr, landbridge?
Sky Bridge, Scale bridge

*purr*

YES! How about a Jimi Hendrix time-traveling bridge as well? I've been enthralled with the idea of lost continents and different theories of evolution since I read this in Anthro 4 years ago. My beliefs are very far out at this point. For example, I believe there was a convergent evolution of an intelligent reptilian race that lives underground. Thanks for the comment.