Evolution and Monkeys on Rafts - Evolution News & Views

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Evolution and Monkeys on Rafts

de Quieroz Monkey.jpg

Writing in the Washington Post, Brendan Borrell has a fascinating review of Alan de Queiroz's book The Monkey's Voyage: How Improbable Journeys Shaped the History of Life. With my comments:

In his engaging new book, "The Monkey's Voyage," de Queiroz makes the case that the vibrant and distinctive biological communities we see today were created by organisms rafting across oceans and soaring through the atmosphere. "The large number of these colonizations tells us that, in the long history of this living world, the miraculous has become the expected," he writes.

Miracles are verboten in science, except Darwinian miracles.

To understand how contentious this notion is, de Queiroz takes us back to the 1950s and '60s, when a wealth of new information emerged about continental drift. Geologists had long recognized that the coasts of South America and Africa fit together like puzzle pieces and had theorized that they were once a single landmass. But now measurements from the ocean floor revealed several ridges, including one in the middle of the Atlantic Ocean, where the sea floor was spreading before the scientists' eyes. These discoveries provided a clear mechanism for how the continents creep along. Geologists determined that, approximately 180 million years ago, there was an ancient uber-continent called Gondwana, which sat on the equator and was composed of what are now South America, Africa, Antarctica, India and Australia. 

Gondwana was also a revelation for evolutionary biologists.

Darwinism draws from reason and revelation.

Its break-up, they surmised, was probably etched in the history of life. For instance, ostriches, emus and rheas, closely related birds found in Africa, Australia and South America, became a textbook example of this continental drift theory. Another famous example were southern beech trees, which are found in South America, Australia and other smaller pieces of Gondwana.

This theory was attractive because it was elegant and sensible, but, as de Queiroz colorfully describes, its proponents became a little too dogmatic about it.

Darwinian dogma

Léon Croizat, a self-trained botanist of French heritage who lived in Venezuela, coined the phrase "Earth and life evolve together" and believed that continental drift explained everything about plant and animal distributions. To him, the idea that plants or animals crossed oceans on their own was outrageous and unscientific. He characterized Darwin as "congenitally not a thinker," in part because of Darwin's suggestion that wolves may have reached the Falkland Islands on icebergs. Croizat came in for criticism himself. An eminent American paleontologist called him "a member of the lunatic fringe."

Croizat criticized Darwinists for insisting that plants and animals crossed oceans on their own, some using rafts, and they call him a lunatic?

Indeed, there had always been evidence that, over the long history of life on Earth, plants and animals made remarkable journeys.

I think this has actually been documented.

Consider, for example, that young spiders are carried on the wind by their silky threads and land on the decks of ships far from the coastline. Freshwater snails cling to the feet of migrating birds. And fishermen on the Caribbean island of Anguilla once watched a natural raft of logs get washed onto shore with 15 green iguanas on it, a species that had not previously existed there.

The Latin name for the new species was Iguana viridis undocumentus.

Proof of how important these journeys are in evolutionary history finally arrived in the late 1990s with genetic-dating studies, such as the one de Quieroz conducted on his garter snakes. We now know that the evolutionary history of ostriches, emus and rheas does not match the break-up of the continents.

Quieroz.jpgThe traditional Darwinian view was that the ratite group (ostriches, emus and rheas) emerged from a flightless common ancestor in Gondwana in the Cretaceous, at the time of the continental break-up. Evolution then proceeded in the different geographies, neatly explaining the modern diversity. The fly in the soup is that the molecular clock doesn't work for that hypothesis. Molecular genealogies suggest that the species diverged too recently to share a common Gondwanaian ancestor.

In fact, the molecular genealogies are screwy, leading industrious evolutionary biologists to invoke land bridges and remarkable transoceanic flying ancestors of flightless birds -- all theories, as you might expect, free of burdensome evidence. A reasonable inference to draw from the implosion of the classical Darwinian genealogy of the ratite group would be that the molecular clock has a gear loose or that there were intrinsic genetic factors (front-loading, etc.) that might explain the biogeography.

The Darwinian inference seems in tatters; maybe they'll rethink their assumptions.

Dream on. 

Some scientists believe that their common ancestor could fly and that they became flightless only after settling on their respective continents. 

Perhaps emus became flightless because they were so damn tired after flying from Gondwana -- "I tell ya', Ethel, I'll never do that again."

Among the other creatures de Queiroz considers are New World monkeys and two other groups of mammals, which apparently rafted to South America on a clump of earth...

I can't get this visual out of my head. A little raft of monkeys setting out on a transoceanic voyage. Gondwana recedes in the sunset. The lugubrious less-adapted competitors watch from the beach. The monkeys would surely have built a raft instead of a clump of dirt -- if they had prehensile thumbs -- but they would have constructed it in an inimitably simian way, with sloppily cut logs and granny knots. Perhaps a pile of bananas stacked in the aft, little bandanas on their heads, and a pirate flag -- crossbones on an Australopithecus skull.

De Queiroz, whose tone is self-effacing and reflective, admits that some may find this view of life unsettling.

I wonder if the emus used rafts. 

Unlike the laws of physics or the seeming order of the periodic table, the distribution of life on Earth has come about through a chaotic chain reaction, like the output of a Rube Goldberg machine.

Or the output of Darwinian theory, which is basically a Rube Goldberg machine. 

Of course, there's another, more romantic way to look at it, which is that life charts its own course.

In evolutionary biogeography, the charted course is in the sea-lanes. There's a whole discipline of evolutionary biology called oceanic dispersal, which posits that the squaring of the screwy molecular clocks and intransigent fossil record with the remarkable geographic diversity of flora and fauna must have been achieved by Huck Finn's ancestors -- monkeys and rodents and iguanas and such -- who set out to sea in little rafts. Such is the conundrum that evolutionary biology faces when the facts don't match the theory. The Darwinian solution? Invoke Mark Twain.

A skeptic might suggest that rethinking Darwinian assumptions might be better than monkeys on rafts. Perhaps the molecular clocks aren't so reliable after all. Perhaps some of the genome is front-loaded, and molecular genealogies wouldn't necessarily square with biogeography. Perhaps something besides natural selection is going on. There's a lot of good science here, just not science consistent with Darwinian premises. 

Darwinism is less a science than a cognitive impediment.


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