When What’s Biological Isn’t Logical, That’s Evolution
By Stan P. Rachootin, Professor of Biological Sciences
The great evolutionary biologist Theodosius Dobzhansky said that “Nothing in biology makes sense except in the light of evolution.”
It is true that any topic in biology, and many scientific questions that impinge on our lives, can be illuminated in revealing and useful ways by considering evolution. How and why does HIV change? Why did domesticated plants and animals happen? What new human diseases are cooking themselves up, and how are they “stirred” by our domesticated animals and “seasoned” with our antibiotics? Can genes from one organism prosper in another? What happens during a mass extinction? What were consciousness, language, and prayer cobbled together from, before there was consciousness or language or religion?
These are reasonable questions, some of which have pretty good (though alarming) answers. We can say with a high level of confidence that life will prosper and advance for billions of years to come. However, the one life form with consciousness, language, and religion— were it looking for a mortgage—would definitely be “subprime,” something only the wildest speculator would want in her portfolio.
But I want to go back to Dobzhansky’s claim about how to make sense in biology. I teach evolutionary theory, how that theory came to be, and about the products of evolution (animals and the inanimate or quasi-animate majority of the living world). In each course, I am struck—and students are annoyed—by how often something can sound logical, but fail to be “biological.”
When we visit Stony Brook below Upper Lake, for example, we find freshwater sponges and freshwater bryozoans. They are all female, and while there are many “co-ed” streams elsewhere, here, the creatures dispensed with sex. And they persist quite nicely, in spite of all we think we know about the point of sex. It’s evolution. On the other hand, an aphid that clones daughters will, with her brood, overwhelm your potted plant. As the plant succumbs, aphids appear with wings; some are males for the first time in generations. These aphids mate and fly off to cause mischief elsewhere. Evolution explains that, too.
I use specific scientific disciplines to explain some of the stories I teach: why a sea anemone has a pharynx; why our genes work in a cascade; why our bodies and those of flies wear out while the bodies of halibuts and lobsters do not. I use physiology, ecology, and developmental biology to fashion these explanations.
But some phenomena are explicable only by evolution. Why are there species? Why will your body reject the generous gift of my kidney, while a grasshopper will accept body parts from an unrelated hopper? Why are there millions of insect species on land and in fresh water but none in the sea? Why does the same gene lead squid, flies, and humans to develop eyes when our common ancestor had no eyes at all? In Fiddler on the Roof, all that did not make logical sense was explained as “tradition.” In biology, we call the same thing “evolution.”
What gets labeled as “evolution” is that which does not fit into the more neatly bounded sciences. If something makes complete sense as ecology, immunology, biochemistry, or genetics, then the story belongs to those fields. The residue is evolution—what does not make sense otherwise.
Occasionally, knotty evolutionary stories can be disentangled and distributed into the other disciplines. There is also the real possibility that much of the history of life is due to dumb luck. Even if an organism’s trajectory makes sense, it is only one of many plausible directions in which it could have developed.
And some aspects of life are just plain idiotic. (For example, the spotted hyena has a particularly long and narrow birth canal (a byproduct of some odd social and hormonal arrangements), but its young have very short placentas. The firstborn always dies during birth, but its passing opens the way for subsequent pups to be born alive.)
Cherry picking among the organelles and organs, the hormones, and the interactions of living things can certainly yield examples that look consistent with what we would expect from an intelligent designer (assuming that our limited understanding suffices to give a complete enough account of what intelligence ought to want to do). But, as Darwin noted, the devil’s chaplain could find just as many stupid, wasteful, and cruel examples for his cause. And biological “perfection” and “idiocy” are often organically intertwined. If it sort of works, and there is currently nothing better, it often persists.
Science consists of asking sensible questions about what we do not currently understand. What we do not understand about biology tends to end up as the central questions of evolution. Patterns in what we do not understand help make our ignorance more organized. And if we think hard about what we know we don’t know (to paraphrase Donald Rumsfeld), we can actually learn a lot about what is probably going on. Evolution teaches humility, and the usefulness of historical narrative. When a problem approaches solution, evolution happily shrinks a bit, as some other area of biology engulfs the emerging answer.
In an earlier Age of Discovery, our knowledge of the world was enhanced by anatomical studies of kangaroos and duckbilled platypuses. In the nineteenth century, naturalists dredged insights from life in the seas’ depths. Today, the worlds revealed by sequencing genes and genomes are just as full of mysteries. But now, scientists “fish” in the gene sequences downloaded from GenBank.
The “things that don’t make sense except …” are still all around. The hardest part is learning to see them.
Learn More:Rachootin’s recommended books and Web sites on evolution:
Books
- The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution, by Sir Richard Dawkins
- The Tinkerer's Accomplice: How Design Emerges from Life Itself, by J. Scott Turner
- The Plausibility of Life: Resolving Darwin's Dilemma, by Marc W. Kirschner, John C. Gerhart, and John Norton
Web Sites
- University of California Museum of Palentology: A well-vetted Web site aimed at high-school and college students is run by paleontologists and integrative biologists at the University of California at Berkeley. The survey of living and fossil organisms, and the basics of evolution, are well covered.
- The National Center for Science Education is at the front line for protecting public schools from the assault on science in the name of creationism and intelligent design. Its executive director, Dr. Eugenie Scott, received an honorary degree from Mount Holyoke in 2006.
