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Common Descent or Common Design? An Exercise in Question-Begging

Jonathan Witt

common design

Darwinists point to similarities across species, classes, and phyla (DNA, for example, crops up practically everywhere in the living world) and argue that this shows we’re all descended from a common ancestor. But to say these similarities demonstrate common descent ignores another possibility. While a common feature may be due to common ancestry, it may instead be due to a common design strategy.

Think of cars. A Jaguar and a Mustang share many features — four wheels, rubber tires, two axles, windshield wipers, lights, gas engines. That doesn’t mean the Mustang evolved from the Jaguar. No, designers reuse design features proven to work for specific engineering needs.

We see this pattern even across disparate technology platforms. In one case the wheel is used and adapted for a water mill. In another case for a bicycle. In another, for a truck.

Looking for the Truth, Not Rigging the Answers

So, what about with living things? Might a designer have used and reused a good design concept in widely different biological contexts? The only way to jump straight from biological similarities to evolution is to rule out the design hypothesis from the start. But if we’re debating evolution vs. intelligent design, then ruling out design is just question-begging. It’s a way to shut down debate and protect modern evolutionary theory from critique.

Someone will object that the design hypothesis “isn’t science.” But that just dresses the question-begging up in a lab coat. It’s still question-begging. And it’s no way to advance knowledge. Science should be about truth-seeking and evidence, not rigged games.

What does the evidence suggest is the better explanation for the origin of new plants and animals in the history of life? Is the best explanation blind evolution, or intelligent design? And what new findings might count in favor of one over the other? Those are the kind of questions an unfettered, truth-seeking scientific culture is happy to explore.

Interestingly, there are many examples of creatures widely separated on the tree of life that still somehow possess this or that unusual feature in common, even though creatures believed to be much more closely related do not share that feature. Evolutionists say such instances are examples of convergent evolution — that is, nature evolved the same unusual feature more than once. So according to Darwinian logic a common feature is prima facie evidence of common ancestry…until it obviously isn’t, at which point it’s time to invoke the magic of convergent evolution.

Such are the lengths Darwinists go to in order to avoid the design inference.

The Case of So-Called “Junk DNA”

Return to the example of DNA. DNA contains information that codes for biological machinery and form. We’re told chimp DNA and human DNA are about 98 percent similar, and that this is just what you’d expect if humans evolved from a chimp-like ancestor. But that figure plummets if you compare bigger units of DNA. And since DNA codes for function, we should expect chimps and humans to share a lot of similar software. Our DNA “software,” after all, is coding for things like blood and bone and muscle, arms, legs, fingers, and toes, eyes and ears, mouth, and nose. These are all things chimps and humans have in common.

A related argument for ape-to-man evolution is that stretches of DNA in humans and chimps seem to be shared bits of junk DNA, bad code left over from genetic mutations long ago, from before chimps and humans split from their common ancestor. No designer would have put the same lines of junk DNA in chimps and humans, the argument goes. It’s a pretty convincing argument at first blush. But today the whole idea of junk DNA is in retreat as geneticists discover more and more uses for stretches of DNA once considered useless. (There are actually multiple problems with the argument. See Chapter 4 of Science & Human Origins for more on this.)

The failure of the junk-DNA hypothesis has larger implications beyond human origins. Darwinian theory led its champions to expect, and predict, that most of our DNA would prove to be junk left over from a blind process of trial-and-error. Intelligent design theorists predicted that, no, most “junk DNA” would prove to have function. The former led to a failed prediction. The latter led to a successful prediction. Score one for the design hypothesis.

Photo credit: JosieLapczynski, via Pixabay.

Cross-posted from The Stream.