Evolution and Parsimony

There's a universally accepted principle of thought which says that given a choice between multiple explanations for a phenomenon the preferred explanation is the one which is simplest and fits all the facts. The principle is sometimes called the Principle of Parsimony, because it stresses that our hypotheses should always be as simple (parsimonious) as the evidence allows.

Mathematician Granville Sewell at Evolution News and Views wrote a piece some years ago inviting us to imagine a scenario illustrating this principle:

A high school science teacher rents a video showing a tornado sweeping through a town, turning houses and cars into rubble. When she attempts to show it to her students, she accidentally runs the video backward .... [T]he students laugh and say, the video is going backwards! The teacher doesn’t want to admit her mistake, so she says: “No, the video is not really going backward. It only looks like it is .... and she proceeds to give some long, detailed, hastily improvised scientific theories on how tornadoes, under the right conditions, really can construct houses and cars.

At the end of the explanation, one student says, “I don’t want to argue with scientists, but wouldn’t it be a lot easier (simpler) to explain if you ran the video the other way?”

That's the most parsimonious explanation of the phenomena depicted in the video, certainly more so than the teacher's contrived explanation, and thus it should be preferred.

Sewell relates this to the problem of undirected Darwinian evolution.

Imagine, he writes, a college professor assigning the final project for students in his evolutionary biology class.

“Here are two pictures,” he says. “One is a drawing of what the Earth must have looked like soon after it formed. The other is a picture of New York City today, with tall buildings full of intelligent humans, computers, TV sets and telephones, with libraries full of science texts and novels, and jet airplanes flying overhead.

Your assignment is to explain how we got from picture one to picture two .... You should explain that 3 or 4 billion years ago a collection of atoms was formed by pure chance with the ability to duplicate itself, and these complex collections of atoms were also able to pass their complex structures on to their descendants generation after generation, even correcting errors that crept in.

Explain how, over a very long time, the accumulation of genetic accidents resulted in greater and greater information content in the DNA of these more and more complicated collections of atoms, and how eventually something called “intelligence” allowed some of these collections of atoms to design buildings and computers and TV sets, and write encyclopedias and science texts....

When one student turns in his essay some days later, he has written, “A few years after picture one was taken, the sun exploded in a supernova, all humans and other animals died, their bodies decayed, and their cells decomposed into simple organic and inorganic compounds. Most of the buildings collapsed immediately into rubble, those that didn’t, crumbled eventually. Most of the computers and TV sets inside were smashed into scrap metal, even those that weren’t, gradually turned into piles of rust, most of the books in the libraries burned up, the rest rotted over time, and you can see see the result in picture two.”

The professor says, “You have reversed the pictures! You did it backwards” “I know,” says the student, “but it was so much easier to explain that way.”

The fictitious student has put his finger on the problem with any theory of biological origins that excludes intelligent agency. The idea that blind chance and the laws of chemistry alone could have conspired to create a living cell, or produce a process as extraordinary as butterfly metamorphosis, or create a structure as unimaginably complex as a human brain requires so many assumptions and ad hoc explanations, so much suspension of incredulity, that it's far simpler, and much more in keeping with our everyday experience, to posit that these marvels were the intended product of an intelligent mind.

Otherwise, Sewell concludes, the process is like a movie running backward. The whole of biological history is as improbable, on naturalism, as assuming that purposeless, undirected forces like tornadoes could actually cause scattered debris to assemble into complex, well-integrated structures.

It's much simpler to assume that an intelligent mind must've somehow been directing the whole process toward a preconceived end.