Some of the great scientific theories unify our knowledge and have fundamentally changed the way we look at the world. Heliocentrism, for example, is the theory that the earth and other planets revolve around the sun. Though at one time it was soundly rejected by the community at large, it best explained the motions of objects in the sky. In science, a theory is an accepted method of interpreting facts. It's based on evidence, and careful observation and cannot be disproved. Evolution, the process by which species change over many generations, is one such theory.
I teach a non-major's intro to bio class. This semester, in fact, we'll be talking about evolution. And, many of them have had just a few days of it. Some have never had it, even though it's required in the state standards in North Carolina as a science, and so that can have repercussions.
That's Dr. Howard Neufeld, professor of biological sciences at Appalachian State University. I asked him, “Why does understanding evolution matter?”
It's the foundation of all biology, of all life. And so it's the most important biological subject. It's important in terms of medicine; if you understand evolutionary biology you can understand how organisms have evolved to be dangerous to humans and other organisms, and you can design strategies to deal with that. It's important just for understanding science, and where we came from.
But, how can one observe evolution, a process that takes place over great spans of time? Can we see it happening or is it a guess?
We see this all the time; we see antibiotic resistance evolving in bacteria. That's a form of evolution. And, when we look at the whole spectrum of life, then what we see is the same processes at work. You know, natural selection, organisms that are better adapted to those conditions leave more offspring for the next generation and so-on. And so, this way we can start asking questions about the interrelationships of living organisms and who's descended from who. The way we do that is, we can look at the DNA and refer relationships, and look at the fossil record. And, you can begin to see that there's a pattern.
Understanding evolution gives us the power to understand what we cannot see, or have yet to find.
If you look at Neil Shubin's work, at the University of Chicago, he said “if we postulate that amphibians made the transition onto land and became reptiles, or became terrestrial amphibians, they should have these characteristics, and they should be found in the layers of the earth that are this approximate age.” Well, that's a prediction, and they went looking over the world. Where are layers of rock that have fossils of that age? And so they looked and looked, and somebody found a snout sticking out of a rock, and there was this organism, Tiktaalik, and it was perfectly intermediate between a fish and amphibian. So in this sense, we used our knowledge of evolutionary science to make a prediction and then Neil Shubin's group confirmed it.
Score one more for the predictive power of science!
Any student that doesn't come away with an appreciation of evolution, which is how all life got to be like it is, is missing the main component of biology. And I like to divide it into two parts: evolutionary facts, and then there's evolutionary theory. The facts are the fossils. The facts are homology and analogy in terms of structure, that many mammals have 5 fingers. If you look at a bat it has five bones in there, and it's just webbing between them to make the wing, and so-on. And DNA evidence. And, we can see natural selection in action. Those are all evolutionary facts, and as I tell students, you cannot deny a fact. Then the theory is, what are the processes by which evolutionary change occurs? We have natural selection, and we can ask how strong or intense those selection pressures are and what ends up in the next generation. And when we put the whole package together, we have a whole comprehensive science of evolution. So, that's how we do it, and I let the students make up their mind.