Does life on earth look designed by an intelligence? Science says no, and evolution explains why.
We’ve been recently looking at Creationist pushback against evolution, an attempted end-run around science to encourage Joe Citizen to put on a lab coat and decide the matter for himself. I summarize the problems with that approach here.
But there’s another way to respond to this version of the Design Argument, which states that nature appears designed by a cosmic Designer. While the bacterial flagellum is a favorite bit of nature that Creationists love to marvel at, DNA itself is even more so. This version of the argument is often expressed like this:
- DNA is information
- Information only comes from designers
- Therefore DNA was designed
- Therefore evolution is inadequate to explain life
- Therefore God.
I’ve summarized this argument before, but I’d like to do it again. In my recent blog post series, I responded by attacking Jim Wallace’s approach. Now I want to set that aside and attack this version of the Design Argument. I will show that DNA is not evolution’s Achilles’ heel but rather a powerful rejection of this argument.
What is the Design Argument?
The Design Argument says that nature looks like it was the product of a Designer. We’ll take humans as our example designers. We know what their designs look like—artwork, airplanes, computers, skyscrapers, and so on. So the claim has become: nature looks like it was the result of human designers who had superhuman capabilities.
Now consider the kinds of constraints these designers work under. By understanding these, we can get an idea of the telltale signs of design and try to find it (or its lack) in DNA. One constraint might be cost: this wristwatch should cost as little as possible. Another might be strength: this bridge should be as strong as possible. Others could be light weight, durability, low maintenance or operating costs, safety, quick completion, long life, beauty, and so on.
Not every design will be burdened by every constraint. For example, cost wasn’t a constraint on the Apollo program, and beauty isn’t a constraint for a circuit board.
How do we attack the Design Argument?
But note one very important omission from the list: junk. No finished design will ever deliberately have unwanted, useless junk in it. A critic might label one element as junk—maybe they didn’t like some architectural ornament—but “junk” would have never been a deliberate part of the design. That makes junk the vulnerable point in the Design Argument. If we can find junk in DNA, we will defeat this argument. In fact, DNA has plenty of junk, in at least five categories.
1. DNA has junk
Human DNA is made up of 3 billion base pairs. Some mammals have less and some more. For example, cows, mice, and bats have more. The axolotl salamander has 32 billion base pairs, and other salamanders have much more. There are grasshoppers, beetles, ticks, worms, and snails with more DNA than humans. There are plants with more. The record holder is an amoeba, with 670 billion base pairs.
There are two explanations. One is that these lifeforms need all their DNA—and the axolotl salamander really needs ten times the DNA that humans have, and the Amoeba dubia really needs 200 times more—but this seems unlikely. The other option is that much of the DNA in earth life is junk.
Just because a stretch of DNA isn’t used for anything now doesn’t mean that it can’t be fodder for evolution to create some future improvement, but this isn’t what we’d expect if life is the way it is because of a designer. However, DNA full of junk is exactly what evolution would predict.
2. DNA has pseudogenes (broken genes)
Human DNA has 20 thousand protein-coding genes, but it also has nearly that many pseudogenes. My favorite example of a pseudogene is that for vitamin C. All but a handful of mammals synthesize their own vitamin C with this gene and don’t need vitamin C in their diets. About 61 million years ago, the ancestors of some primates, including humans, lost this ability when the working gene became a pseudogene. Every cell in your body contains this useless, nonworking pseudogene.
Another example is humans’ 390 genes for smell. There are also 480 pseudogenes for smell. These pseudogenes look similar enough and are in roughly the same place compared to other animals’ working genes that the evolution from gene to pseudogene is clear.
DNA full of pseudogenes is what evolution would predict, not what a Designer would create.
3. DNA has endogenous retroviruses
Viruses can’t reproduce on their own and must force a cell to do it. Sometimes a virus will infect the DNA in a germ cell (an egg or sperm). If that viral DNA is inactivated by mutation, the genome is passed down to future generations with a record of this viral invasion. Human DNA has roughly 100,000 nonworking fragments of these viruses, a record of millions of years of viral attacks, composing 5 to 8 percent of the total number of base pairs.
4. DNA has atavisms
The novel and movie Jurassic Park imagine finding dinosaur blood fossilized in ancient mosquitoes preserved in amber. In the blood is fragmentary DNA, intact enough to reconstruct dinosaurs. It doesn’t work like that back here in the real world, but biologists might be able to do it the other way around by (for example) reactivating genes for tooth formation in dinosaurs’ modern descendants, birds. Birds don’t have teeth, but their theropod dinosaur ancestors did.
5. DNA has vestigial structures
Vestigial structures are structures like the human appendix or tailbone that have lost most or all of their ancestral function. That doesn’t mean that they’re useless, just that they aren’t used for what they were originally used for. For example, ostrich wings are vestigial because they can’t be used to fly (that’s what wings do), but they’re still useful.
Other examples are eyes in blind mole rats or cave fish, the pelvis (for nonexistent legs) in the baleen whale, and goose bumps (to raise nonexistent fur) in humans.
What this shows (and doesn’t show)
The success of this argument doesn’t prove that God didn’t create DNA. He might have his own ways of design that are beyond our capabilities to appreciate. It also doesn’t prove that God doesn’t exist. God could still exist while letting evolution shape life.
But this does defeat the popular DNA version of the Design Argument, which says that DNA looks like it was designed. If God’s handiwork is so bizarre that it doesn’t look like anything that any conceivable designer would likely create, then Christians should rethink the Design Argument.
it’s about the world’s population killing each other
until there’s only 2 people left,
and then the woman pukes an apple
and they both get naked.
— Macaulay Culkin