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Arrival of the Fittest: Natural Selection as an Incantation


In 1904, genetics pioneer Hugo de Vries quipped that "natural selection may explain the survival of the fittest, but it cannot explain the arrival of the fittest." In 2014, Andreas Wagner thinks it can. His new book, reviewed by Mark Pagel in Nature, is titled Arrival of the Fittest: Solving Evolution's Greatest Puzzle. What is that "greatest puzzle"? The ability to work miracles. That's right: Pagel begins his review:

You inhabit something of a miracle, in engineering terms. Your body consists of trillions of cells, woven together into something whose complexity far outstrips that of the most sophisticated objects our best engineers can produce, from computers and skyscrapers to space shuttles. A relatively simple outer form belies a teeming society of chemical reactions and protein engineering. This must maintain itself within strict temperature and physiological limits while enduring a complex and frequently unpredictable external environment. And, to achieve its long lifespan, it must avoid the sort of catastrophic breakdown that plagues human-engineered objects. (Emphasis added.)

With this glorious opening, Pagel praises Wagner for solving evolution's greatest puzzle. It's so simple, it's astonishing nobody thought of it before:

All the breathtaking innovation required to produce this complexity rests on two pillars of evolution that are, for the most part, either ignored or unappreciated. These are robustness and evolvability, which together grant what evolutionary biologist Andreas Wagner calls "innovability" in his engaging and intelligent Arrival of the Fittest. Wagner's message is that these two foundation stones of evolution exist because of an unexpected and remarkable degree of neighbourliness (not his term) that seems to characterize life -- a neighbourliness that allows species to innovate more rapidly and successfully than previously imagined.

This makes about as much sense as a wizard telling a pile of rocks, "Go forth and innovate! Let evolvability grant thee engineering power! Be thou robust forthwith, and with thy neighboring rocks at thy aid, bring forth! Bring forth!" Pagel and Wagner have just ascribed godlike powers to material objects, as if the incantation "natural selection!" can make an albatross out of a squid. Invent a phrase with magical powers that can do anything. That's natural selection.

What bothered Hugo de Vries was the innovation problem. He granted the "survival of the fittest," but disputed the power of natural selection to create things. That's why he and other early-20th-century evolutionists looked for better sources of innovation than Darwin had dreamt of. He thought he found them in mutations. His ideas eventually fed into the "modern synthesis" of neo-Darwinism: genetic mutations acted on by natural selection.

Mark Pagel, an evolutionary biologist at the University of Reading, has been critical of gradualism in the past, tending toward punctuated equilibria instead (e.g., see here and here). He has also criticized Darwinian sub-theories like the "Red Queen" hypothesis (the idea that evolution must keep moving to stay in place; see here) and simplistic presentations of evolution (here). But something about Wagner's book has enraptured him. It's as if, after 155 years of evolutionary theorizing since Darwin supposedly solved "evolution's greatest puzzle," someone finally actually solved it:

He pictures the solution as a balance between extremes:

Think of a rigid, riveted steel girder. It is, in many respects, a robust object, able to bear weight and resist high temperatures. But it is not evolvable -- there is nothing it can be but a girder. Now think of the most evanescent thing you can, perhaps a wisp of smoke in a breeze. It is highly evolvable -- it can change -- but it is not at all robust. The wonder of you and me and albatrosses is that we are not only robust, but also evolvable. Equally wonderful is that life as we know it would not be possible any other way.

This is a false dichotomy wrapped in an "assuming the consequent" fallacy. Having ruled out intelligence as a cause, he is stuck with this syllogism: Major premise: Innovation must be explained by unguided natural selection. Minor premise: If life were not robust and evolvable, it could not exist. Conclusion: Robust and evolvable unguided natural selection creates innovation. Simply repeat the incantation "natural selection." It has robustness and evolvability built in.

Pagel's review gets into the "search space" problem widely discussed in William Dembski's books. How can blind, aimless processes find the buried treasure on the island without a map?

To get from simple replicating molecules through to single-celled organisms such as bacteria and eventually on to complex and ungainly multicellular organisms like giant squid, natural selection has had to search through a vast library of varieties and combinations of genes. Now, imagine you are in the squid section of the library and you want to make an albatross. Every step along the way has to be something that works: it has to be a competitive organism.

This is classical gradualistic Darwinism, but he has snuck in a goal: "you" are in the squid section, and "you want" to make an albatross. We must not let that personification cloud our thinking as he proceeds to describe Wagner's deep insight: the shortcut to the buried treasure:

Wagner has discovered what makes this search possible. It is good neighbours, and lots of them. The genes that make our bodies typically do not act alone. Instead, they form large and complex networks that interact to produce metabolisms, tissues and organs. Wagner has built computer models of these networks in which he randomly alters some feature, mimicking in silico the sort of random mutation that natural selection relies on. He then asks whether the mutated network as a whole can still perform the job it was designed to do.

"The job it was designed to do..." Pagel and Wagner are so near, yet so far. The book description on Amazon claims that natural laws drive evolution to the treasure in record time:

In Arrival of the Fittest, renowned evolutionary biologist Andreas Wagner draws on over fifteen years of research to present the missing piece in Darwin's theory. Using experimental and computational technologies that were heretofore unimagined, he has found that adaptations are not just driven by chance, but by a set of laws that allow nature to discover new molecules and mechanisms in a fraction of the time that random variation would take.

Once again, as with Avida and all the other computer models, we find that Wagner has snuck extra information into the system. As Dembski showed in No Free Lunch, no evolutionary algorithm is superior to blind search. Without design, there is no shortcut to the treasure.

To make the hunt easier for evolution, Wagner imagines a fantasy land with treasures all over the place, right near each other: "Wagner finds that he does not have to travel very far along these mutational pathways before he encounters new neighbourhoods, where the networks produce different products," Pagel explains sympathetically while personifying evolution. "For instance, a network that can consume glucose might lie near one that can consume other fuels, such as acetate." Yes, and if a squid had wings, it could fly like an albatross. After all, they are neighbors.

If you are not convinced by this explanation for the "breathtaking innovation required" for your body that Pagel so aptly described in his opening, you will probably yawn at his ending sales pitch:

This offers an answer to one of the most fundamental questions of evolution: how has natural selection had time to search the almost limitless library of life? The answer, posits Wagner, is that it does not usually have to search very far: squid and albatrosses are closer neighbours than we might have expected. Arrival of the Fittest will give you a new appreciation of the sheer improbability, but also the plausibility, of the diversity of life.

These simplistic propositions would wither before Dembski's No Free Lunch and Meyer's Signature in the Cell, but since Nature is unfriendly to challenges to natural selection, Pagel's endorsement echoes around the world. The unreflective now know how the squid took wing and began to fly.