I was finally able to just sit down and read this book. First of all, let me say that this book a pleasure to read. While it follows the moderately standard format of popular science books (history of the concept, the concept itself, and then future considerations), Dr. de Queiroz is a very good writer. His writing is clear, articulate, and liberally interspersed with asides, anecdotes, and humorous exchanges that bring life to what would be an otherwise dry topic.
Biogeography is an interesting science and one that is, at least mentioned, in any historical geology or historical biology course. The basic question is “How do similar species appear on two widely separate continents?” The Monkey’s Voyage: How Improbable Journeys Shaped the History of Life brings some excellent science to the table and pushes for a explanation that defies common sense… and yet remains the best explanation for the phenomenon.
I came to this book, being highly skeptical. I was taught old school biogeography. The reason that so many similar species existed on separate continents was because of plate tectonics. All the species were present, then separated with the continents about 110 million years ago. Indeed, I was somewhat miffed that this book challenged that notion.
But (and take note creationists, because this is how you overturn an established scientific paradigm), Dr. de Queiroz has provided an abundance of evidence that the common knowledge is not the case. What de Queiroz does here is describe dozens of case of deep scientific inquiry. Through the use of geological, biomolecular, and paleontological data, he destroys the idea that biogeography is only about the breakup of Gondwana.
That’s not to say that some species dispersal is the from the Gondwana break up, but it is flatly impossible that all of it. Indeed, it seems that the majority of cases are from something that’s almost scary to contemplate. It hasn’t been continental breakups at all. It appears to have been mostly ocean voyages.
This book documents case after case, ranging from frogs to the New World Monkeys that simply couldn’t have dispersed via continental breakup. The genetics don’t match a continental break up scenario. The fossil history doesn’t match a continental break up scenario. And the time frames don’t match a continental break up scenario.
Unlike what creationists do, de Queiroz has both used a significant amount of evidence, from a variety of areas, to show that the current explanation doesn’t make sense. And he is able to show how his ideas (well, those of the oceanic dispersal supporters) do make sense.
The single best example is that of the New World Monkeys. This illustration pretty much explains everything. (click to enlarge)
The gray bar in the cladorgam shows the estimated time of the split between New World Monkeys (Americas) and the Old World Monkeys (Africa and Asia). Even using the best possible circumstance and some dodgy data, researchers were only able to generate a most distant divergence time of about 71 million years ago. The fossil record of New World Monkeys apparently just begins about 26 million years ago.
That gray bar shows the best estimate (ignoring the one paper that suggest 71 mya). Now, way over on the left, at about 110 million years ago, is the separation of Africa and South America and the beginnings of the Atlantic Ocean.
That’s well before the earliest record of primates even existing. The earliest ancestor of the primates is estimated to have lived about 85 million years ago. Long after the supercontinent break. Yet New World Monkeys exist. There is no fossil record of that group of primates travelling up through Africa and Asia, across a land bridge to North America and then down to South America.
The only reasonable explanation is that the monkeys crossed the Atlantic. At the time, it would have only been a journey of about 900 miles. It could have been several journeys of just a few hundred miles as the Atlantic of the time had many islands.
In another set of examples, we read about the mysterious amphibians of an island off the west coast of Africa. Islands that are volcanic in nature and simply didn’t exist until 80 millions years after Gondwana broke apart. Amphibians, with their water permeable skin would be poor candidates for an ocean crossing. Yet, there they are on volcanic islands that have no business having amphibians.
What’s even more interesting is that genetic studies of these amphibians show that their closest relatives are not from the west coast of Africa, but way over on the east side of Africa. In fact, they are very near to the Congo. Which just happens to dump so much fresh water into the ocean around the mouth that is lowers the salinity near the surface. And that there is a strong current from the south pushing river water (and any vegetation rafts) northward, right into the islands that are a mere 400 miles from the mouth of the Congo.
While the two stories I relate here may seem somewhat contrived, there are many similar stories in the book. All backed with significant amounts of evidence that show the old biogeographical explanation don’t match the data and ocean crossings can match the data.
Notice that I said “can”. The author does not demand that ocean crossings of all these species is exactly how it happened and he’s right to insist that we will probably never know exactly how these species came to be where they are. He does present considerable evidence to support his ideas and I find myself convinced. When I’ve nothing else to do for a few days, I’ll hit up his references and confirm the claims he makes.
The book isn’t without its faults. I’m not a fan of his vague and possibly mistaken view of the Big Bang Theory, but it is short and doesn’t really impact the evidence he presents and that is what popular science books should do. Present the evidence in simple language, explain why we think one way, and present why we should be thinking another way.
The author could have spent 500 pages claiming that plate tectonics couldn’t have caused the dispersal pattern we see and his ideas were obviously correct. But he didn’t. He explained, for multiple cases, in detail, why the data collected and published (not by the author) show that the current paradigm is wrong. He gives numerous examples showing how animals can survive long ocean journeys (including one example of a pregnant woman washed out to see in the aftermath of the Indian Ocean earthquake). He takes considerable pains to not demand that we accept his point of view, but leads us along a path of discovery.
For the skeptical thinker and the armchair scientist, this book is well worth the effort. I really enjoyed it. I must say that the argument is quite compelling. I’ll put this book up, in spite of the relative obscurity of the subject matter, with the best of Sagan.