Need We Say It? "Directed Evolution" Is a Contradiction in Terms - Evolution News & Views

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Need We Say It? "Directed Evolution" Is a Contradiction in Terms

Behold this curious headline: "First Artificial Enzyme Created by Evolution in a Test Tube." If it was "created" by evolution, the term "evolution" has surely lost all meaning.

The announcement from University of Minnesota states that Burckhard Seelig and a team at the university used "directed evolution" to create a new functional enzyme.

There's a wobbly new biochemical structure in Burckhard Seelig's lab at the University of Minnesota that may resemble what enzymes looked like billions of years ago, when life on earth began to evolve - long before they became ingredients for new and improved products, from detergents to foods and fuels. (Emphasis added.)
Directed evolution is to be distinguished from "rational design," the article explains. Rational design implies a preconceived plan, but directed evolution is different:
Rational enzyme design relies on preconceived notions of what a new enzyme should look like and how it should function. In contrast, directed evolution involves producing a large quantity of candidate proteins and screening several generations to produce one with the desired function. With this approach, the outcome isn't limited by current knowledge of enzyme structure.
The candidate proteins were "screened" to "produce" one with the "desired function." If screening something for a desired function is not rational design, what is it? It is certainly not neo-Darwinism, which of course has neither plan, desire, nor function. Yet the news release makes it sound as if what Seelig did is no different from what natural selection does:
While a handful of groups worldwide are developing artificial enzymes, they use rational design to construct the proteins on computers. Instead, the Seelig lab employs directed evolution. "To my knowledge, our enzyme is the only entirely artificial enzyme created in a test tube by simply following the principles of natural selection and evolution," he says.
This is not "natural selection and evolution." It is artificial selection -- a form of intelligent design. Artificial selection implies intelligent minds selecting roses, cattle, dogs or any other living organisms for a "desired function." It doesn't matter if the intelligent agent works by creating a random pool to select from, or outlines a carefully planned sequence of rational steps: selection by a mind for a purpose is intelligent design.

The fallacies continue:

"Just as in nature, only the fittest survive after each successive generation," Seelig explains. The process continues until it produces an enzyme that efficiently catalyzes a desired biochemical reaction. In this case, the new enzyme joins two pieces of RNA together.
This has nothing to do with neo-Darwinism, which has no desires. A breeder can make anything "survive" if he selects it and only allows his selection to reproduce. Seelig is employing intelligent design from start to finish. If he kept his interfering hands to himself and let nature take its course, would his enzymes compete in the soil or the ocean? If he were truly "following the principles of natural selection and evolution," he would have to cast the ingredients out into the world and walk away.
"It's kind of like giving typewriters to monkeys," he says. "One monkey and one typewriter won't produce anything clever. But if you have enough monkeys and typewriters, eventually one of them will write 'to be or not to be'." The lottery provides another analogy. "If you buy more tickets, you're more likely to win," Seelig says.
Once again, these analogies are highly misleading. You can't win a lottery no matter how many times you play if there is no target sequence to aim for that players and judges agree on. The Shakespearean phrase does nothing without an intelligent reader searching for the sequence of letters and selecting them for a purpose. It means nothing outside the context of English literature and philosophy. (In real experiments with monkeys, they tend to urinate on the keyboard or break the typewriter long before typing much of anything.)

Here's another instance of "investigator interference": Seelig's team undoubtedly selected all one-handed amino acids for the experiment. No enzyme would have resulted from a two-handed, racemic mixture: just a tangled glob of polypeptide.

"Enzymes have always fascinated me," he says. "It's rewarding to do work that has practical applications yet provides the opportunity to better understand how life on earth evolved."
Detection of the fallacy in that quote is left as an exercise.


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