Why Evolution Is True

Francisco Ayala on “Signature in the Cell”

by Matthew Cobb

Jerry, on his way to the Galapagos, asked me to post this. Over at Biologos, “Science and the Sacred” has persuaded Francisco Ayala  to write a review of Stephen C. Meyer’s Signature in the Cell. Here it is. There’s a debate going on over there, too.

How should a person of faith respond to Signature of the Cell? I am an evolutionary scientist who would suggest the following considerations.

The keystone argument of Signature of the Cell is that chance, by itself, cannot account for the genetic information found in the genomes of organisms. I agree. And so does every evolutionary scientist, I presume. Why, then, spend chapter after chapter and hundreds of pages of elegant prose to argue the point? It is as if in a book about New York, the author would tell us that New York is not in Europe, and then dedicate most of the book to advancing evidence that, indeed, truly, New York is not in Europe.

Signature of the Cell offers Intelligent Design (ID) as the alternative explanation to chance in order to account for genetic information. This suggestion turns out to be no more convincing than a proposal by the author of the book about New York, who having exhausted all possible ways of telling us that New York is not in Europe, would now offer Peoria as the alternative city to visit. We would rather read about New York’s architecture, splendid avenues, and great parks; about the rich culture and ethnic diversity of the city; about its restaurants, concert venues, theatres, and wonderful sights in and around the city. But regarding natural selection, genetics, ecology, development, physiology, and behavior in the evolution of genetic information, there is nothing substantive in Signature of the Cell.

Christians and other people of faith should be troubled about Signature of the Cell for several reasons. One is that Meyer avoids consideration of the negative implications of ID as an explanation of the origin of genetic information, which is his main subject. According to Meyer, ID provides a more satisfactory explanation of the human genome than evolution does. ID’s explanations envision “discrete or discontinuous intelligent activity in the history of life” (p. 481). Scientists have now obtained the complete DNA sequence of the human genome. The genome has a length of about three billion nucleotides, the “letters” of the DNA alphabet. Scientists have also obtained the complete DNA sequence of the chimpanzee genome—also three billion letters long—and of several hundred other species of organisms. How can we envision the “discrete or discontinuous activity” of the Intelligent Designer? The human and chimpanzee genomes differ from each other in just a few percent of the DNA letters, less than two percent in the genes that code for proteins. Did the Designer tweak the chimpanzee genome to make the human genome? Or, perhaps more likely, did the Designer use a preexisting genome and tweak it a bit to make the human genome and tweak it a different way to make the chimpanzee genome? Did the Designer go on tweaking genomes a bit at a time to design the genome of the gorilla and other primates, and more and more tweaking for other animals, all the way down to mice, and even to fruitflies, with which we share a good fraction of the genome?

The human genome includes about twenty-five thousand genes and lots of other (mostly short) switch sequences, which turn on and off genes in different tissues and at different times and play other functional roles. There are also lots and lots of DNA sequences that are nonsensical. For example, there are about one million virtually identical Alu sequences that are each three-hundred letters (nucleotides) long and are spread throughout the human genome. Think about it: there are in the human genome about twenty-five thousand genes, but one million interspersed Alu sequences; forty times more Alu sequences than genes. It is as if the editor of Signature of the Cell would have inserted between every two pages of Meyer’s book, forty additional pages, each containing the same three hundred letters. Likely, Meyer would not think of his editor as being “intelligent.” Would a function ever be found for these one million nearly identical Alu sequences? It seems most unlikely. In fact, we know how these sequences come about: one new Alu sequence appears in the genome for every ten newborns, generation after generation. The Designer at work? Unlikely: many of these sequences damage the genome causing abortion of the fetus during the early weeks of life.

Perhaps one could attribute the obnoxious presence of the Alu sequences to degenerative biological processes that are not the result of ID. But was the Designer incompetent or malevolent in not avoiding the eventuality of this degeneration? Come to think of it: why is it that most species become extinct? More than two million species of organisms now live on Earth. But the fossil record shows that more than ninety-nine percent of all species that ever lived became extinct. That is more than one billion extinct species. How come? Is this dreadful waste an outcome intended by the Designer? Or is extinction an outcome of degeneration of genetic information and biological processes? If so, was the Designer not intelligent enough or benevolent enough to avoid the enormity of this waste?

Meyer asserts that the theory of intelligent design has religious implications. “Those who believe in a transcendent God may, therefore, find support for their belief from the biological evidence that supports the theory of intelligent design” (p. 444). I do think that people of faith may find in the world many reasons that support their belief in God. But I don’t think that intelligent design is one of them. Quite the contrary. Indeed, there are good reasons to reject ID on religious grounds, in addition to scientific grounds. The biological information encased in the genome determines the traits that the developing organism will have, in humans as well as in other organisms. But humans are chock-full of design defects. We have a jaw that is not sufficiently large to accommodate all of our teeth, so that wisdom teeth have to be removed and other teeth straightened by an orthodontist. Our backbone is less than well designed for our bipedal gait, resulting in back pain and other problems in late life. The birth canal is too narrow for the head of the newborn to pass easily through it, so that millions of innocent babies—and their mothers—have died in childbirth throughout human history.

I could go on about human features that betray a design that certainly is not intelligent. I will add only one more consideration. More that twenty percent of all human pregnancies end in spontaneous abortion during the first two months of pregnancy. That is because the human genome, the human reproductive system, is so poorly designed. Do I want to attribute this egregiously defective design to God, to the omnipotent and benevolent God of the Christian faith? No, I don’t. It would not do to say that God designed intelligently the human genome and that it then decayed owing to natural processes. If God would have designed the human genome, surely He would have done it so that this enormous misfortune would not happen. Think of it: twenty percent of all human pregnancies amount to twenty million abortions every year. I shudder at the thought of this calamity being attributed to God’s specific design of the human genome. To me, this attribution would amount to blasphemy.

Before the scientific revolution of the sixteenth and seventeenth centuries, earthquakes, volcanic eruptions, and the like were attributed to direct action by God, so that the tsunami that five years ago killed two hundred fifty thousand Sumatrans might have been interpreted as God’s punishment. Now we know that these catastrophes are the result of natural processes. Similarly, people of faith would do better to attribute the mishaps caused by defective genomes to the vagaries of natural selection and other processes of biological evolution, rather than to God’s design.

h/t: Darrel Falk