Vestigial Organs: Evidence for Evolution (Part 5)

“If you were going to design a person from the ground up,” the professor declared, addressing my third-year zoology class, “you wouldn’t design a person the way we are now. We have all sorts of problems as a result of our evolutionary history.”

At the front of the lecture hall, a screen displayed a human body diagram labeled with “vestigial structures.” Thought to offer evidence for evolution, these structures supposedly performed functions in humans’ evolutionary ancestors but now serve either no function, a reduced function, or a different function. The textbook from another class I’d taken explained vestigial structures this way:

The adaptions of organisms have long been, and still are, cited by creationists as evidence of the Creator’s wise beneficence, but no such claim can be made for the features, displayed by almost every species, that served a function in the species’ ancestors, but do so no longer. Cave-dwelling fishes and other animals display eyes in every stage of degeneration. Flightless beetles retain rudimentary wings, concealed in some species beneath fused wing covers that would not permit the wings to be spread even if there were reason to do so. In The Descent of Man, Darwin listed a dozen vestigial features in the human body, some of which occur only as uncommon varieties. They include the appendix, the [tailbone], rudimentary muscles that enable some people to move their ears or scalp, and the posterior molars, or wisdom teeth, that fail to erupt, or do so aberrantly, in many people.

My textbooks also listed the reduced hindlimbs in some fossil snakes and bones dubbed “vestigial hips” in whales as evidence for evolution. Other articles have addressed such claims in detail, so for now, let’s look at how to think through “vestigial structure” arguments more generally using some of the 7 Checks of Critical Thinking.

Check #1: Check Scripture

Genesis indicates God created living things to reproduce according to their kinds. So, from a biblical perspective, we wouldn’t interpret so-called vestigial structures as leftovers from one kind of creature evolving into another. Because Genesis also reveals that God called everything he’d made very good,1 we wouldn’t predict that God originally designed completely useless features in living things. However, Genesis also explains creation didn’t stay “very good,” thanks to human sin. This means we shouldn’t be surprised to see loss or degeneration of structures within kinds of living things. Biblically, then, we’d expect that “vestigial structures” likely fit within one of two categories:

• Good design features which have sustained a loss, reduction, or degeneration of function.
• Good design features which still serve their original important functions.

Check #6: Check the Interpretations

Sure enough, when we jump2 to Check 6 to examine the observational science of “vestigial structures,” we find the structures usually do fall into one of these two categories. For example, cave fish losing functional eyes,3 beetles losing functional wings, or snakes potentially losing limbs4 would all be cases of lost genetic information within kinds of living things. But evolving one kind of creature from another would at some point require the gain of functional new genetic information.

On the other hand, structures Darwin called vestigial in humans do tend to serve important functions. For example, the tailbone is a crucial anchoring point for muscles that support internal organs. The appendix plays a role in immunity as a reservoir for helpful bacteria. Even pelvic bones in whales serve essential reproductive functions, as a study reported in the journal Evolution the year after my textbook edition was published.5 And what about wisdom teeth? Interestingly, wisdom teeth don’t often cause problems in humans living on non-modern diets, but modern processed food seems to have contributed to wisdom tooth issues since the 1800s.6 Again, this instance illustrates degeneration of an originally good design.

Check #7: Check the Logic

Now let’s take a step back to examine the assumptions behind vestigial structure arguments. For vestigial structures to be evidence for microbes-to-man evolution, vestigial structures must exist. But for a structure to be considered vestigial—that is, an evolutionary leftover, evolution would have to be true. So, these arguments must assume evolution is true in order to claim that evolution is true. Does anyone smell circular reasoning?

Some might still argue that evolution predicts vestigial structures, so their presence confirms evolution. Basically, the argument states,

If evolution is true, then some structures will be functionless leftovers.
Some structures are functionless leftovers.
Therefore, evolution is true.

This argument might sound convincing. But besides the problem that calling structures “functionless” runs into the same trouble as claims about “bad designs” in nature, this argument relies on a fallacy called Affirming the Consequent.7 In other words, even if “functionless” structures existed, that would not logically entail evolution is true.

Summing Up

Altogether, the observable facts about “vestigial structures” are consistent with a biblical worldview and need no explanation from evolutionary assumptions. A bit of biblical, critical thinking reveals these structures are not the clear-cut evidence for evolution which textbooks can make them appear. Instead, they typically represent either genetic information losses within kinds of living things or perfectly functional designs—reflecting their Perfect Designer.

For more on how to think critically about any faith-challenging message, stay tuned for future blog articles and my new video series, CT (Critical Thinking) Scan, available now on the AiG Canada YouTube channel, the AiG Canada Facebook page and Answers.TV.