The Dispersal of Doubt: Biogeography, Convenient Omission, and Selective Quotation

A common loon rests on a mat of floating vegetation.

I recently encountered an article that is a classic demonstration of the array of deceptive tactics employed by a well-known critic of evolutionary theory. In a relatively brief essay about biogeography, the critic raises as many doubts as possible through the use of selective quotations from actual experts on the topic. All the while, he conveniently omits important details from the quoted texts that actually reduce the purported severity of the highlighted "conundrums."

In particular, the critic fails to apprise his readers of the following details related to the “rafting hypothesis” for the origin South American monkeys:

  1. There were numerous volcanic islands interspersed between the two continental land masses during the Eocene epoch, potentially making the dispersal distances shorter than the barrier of "hundreds, if not thousands, of kilometers of open ocean" erected by the critic. In fact, drilling studies have shown evidence of subaerial exposure as late as 25 million years ago in the South Atlantic. These points are now more than 1 km below sea level. Of course, the critic does not bother to mention any of this.
  2. The prevailing winds and ocean currents moved westward across the South Atlantic during the Eocene. Peer-reviewed models have shown that these movements would have substantially aided the migration of a floating island across the Atlantic. The most conservative scenarios predict that a large raft of floating vegetation could have made the journey from Africa to South America in as little as 8 days at 50 million years ago, 11 days at 40 million years ago, and 15 days at 30 million years ago. Again, the critic does not bother to mention any of this.
  3. An extended rafting event across the Atlantic would likely have necessitated a floating island of vegetation with an adequate supply of food and water. However, such natural rafts are known to exist. In addition, studies of water deprivation in modern primates suggest that a hypothetical proto-platyrrhine monkey could have survived without fresh water for at least 13 days, fitting nicely within the 8-15 day range suggested by the wind and ocean current models mentioned above. Once again, the critic does not bother to mention any of this. Instead, he makes a joke about monkeys building rafts and stocking them with provisions for their voyage.
  4. Evidence of South American monkeys first appears in the fossil record soon after a major drop in sea level about 35 million years ago. A drop in sea level at this time would have further reduced the distances separating the continental land masses and the exposed volcanic islands of the South Atlantic, making an incremental, island-hopping scenario more plausible. By now, it should come as no surprise that the critic does not bother to mention this drop in sea level, either.

Clearly, these disregarded details do not completely solve the puzzle of the origin of South American monkeys. However, when considered as a whole, they make the proposed "rafting hypothesis" much more plausible. Moreover, they illustrate an important aspect of evolutionary theory that distinguishes it from the alternative "explanations" generally favored by the theory's critics.

Unlike the doctrine of special creation (let's just call it what it is), the theory of evolution is actually testable.

From the existence of fossil intermediates to the discovery of plagiarized errors in molecular sequence data, evolution helps us make sense out of a large set of scientific observations. But evolutionary theory can also be used to generate new, testable hypotheses. This is quickly revealed by a perusal of the very scientific literature from which the critic cherry-picked quotes in his attempt to ridicule the notion of "seafaring monkeys." In reality, when such biogeographical puzzles are identified, the framework of common descent allows scientists to propose possible scenarios and construct testable hypotheses based on those scenarios.

It should come as no surprise when the resulting research bolsters the plausibility of the proposed evolutionary scenario. This is exactly what one should expect from a robust and comprehensive scientific explanation like evolution.

Sadly, the deceptive tactics displayed by this critic of evolution are also to be expected. Without a testable, scientific alternative, he must resort to setting adrift as many doubts about evolution as possible, hoping to ensure that at least one survives to make landfall in a "renewed" world.

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9 Responses to “The Dispersal of Doubt: Biogeography, Convenient Omission, and Selective Quotation”

  1. I posted on the idiocy of I.D. responses to the evolutionary evidence for biogeography here

    There is also a link to a neat video about the geographical distribution of proto mammals and mammals as the continents moved.

  2. RBH says:

    Huh. Casey Luskin. ‘Nuff said.

  3. Bill Farrell says:

    Not surprisingly, Luskin is a “senior” editor at the on-line Salvo magazine site where he published this article. Also the Editorial and Advisory Board reads like the phone directory at the Discovery Institute. Of course, self-publication is nothing new for Luskin or the other Discoveriods for that matter.

    Alas, lying by omission is standard Discovery Institute practice. They rely upon their readers to take what they say at face value, although a 5-minute Google search can usually uncover what’s really going on.

    Monkey business, indeed. Oh, the irony.

  4. Jeremy Mohn says:

    It turns out that he has written about this topic several times before, each time using pretty much the same quotations and arguments. It’s as though he keeps a list of cherry-picked quotes at his fingertips, ready to be woven into his next screed whenever needed. Perhaps it is easier to convince yourself that you are acting with honest intentions when the source material has already been divorced from it’s original context?

  5. Wayne says:

    Glad that you posted this, Jeremy. Casey Luskin does the same routinely in every post he makes critiquing evolution at the ID site At one glance, those articles would seem convincing to lay readers & students and leave doubts & confusions regarding evolution in their minds. That’s exactly what the Discovery Institute wants.

  6. Jeremy Mohn says:


    Thanks for posting the link to your blog. Sorry it got caught in my spam folder.

    I especially appreciated you pointing out that the dispersal event that led to New World monkeys is actually expected to have been a one-time occurrence, due to the genetic evidence that shows all South American monkeys share a single common ancestor. If the dispersal route had been more readily accessible for back-and-forth migration between the continental land masses, the platyrrhines and catarrhines would likely not cluster so tightly in our molecular phylogenies.

  7. Ted Lawry says:

    Very interesting. The evolution of trichromatic color vision in Old and New World primates is a classic case, but I hadn’t heard of the New World monkey origin problem. Could you provide references to the sources you cite?

  8. Jeremy Mohn says:


    Most of the sources are those originally quoted in the article. The critic did a good job of citing his sources (but a poor job of representing them accurately). You can find the references listed at the end of the article.

    It certainly would have been helpful for me to cite the sources myself. I will attempt to add those to the post when I have time.

  9. EJH says:

    South American caviomorph rodents are also believed to have rafted over from Africa around the same timeframe as the ancestors of platyrrhines. Casey refers to them in his article with reference to John C Briggs’ Elsevier title as a source. I’m sure Briggs must mention the rafting hypothesis for the caviomorphs as well, but Casey misses the fact that this actually constitutes collaborating evidence for platyrrhine rafting. Um, I guess that’s being to kind to Casey as he likely didn’t miss anything; rather he’s once again selectively ignoring the evidence in favor of common descent.

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