Evolution 101

Saturday, June 17, 2006

What are the Practical Applications of Evolution?

If this humble podcast isn’t enough Dr. Zach to fill your week, please go and check out the podcast produced by the New England Skeptical Society called the “Skeptic’s Guide to the Universe.” I was interviewed this week for their podcast, and had an absolutely excellent time. I know that most of you who subscribe to my via iTunes already know how excellent their show is, so I’m really just telling everyone else- if you like evolution, there are so many other topics germane to skepticism, and they do an excellent job of covering them.

Now, some of you may be thinking, “Here we’ve come 20 weeks, and I’ve never heard a single practical use of evolution.” In fact, this is a pretty common criticism of evolutionary theory, but it’s a criticism that doesn’t really take into account what science is.

Science is an exploratory, explanatory process. Science affords us the opportunity to ask questions about the way the world works, and be reasonably sure that the answers we find actually correspond with reality. This makes the knowledge associated with scientific inquiry significantly different from the knowledge associated with, say, superstition. While superstition will explain reality according to seemingly unrelated phenomena, such as one’s success in life and the color of cats that happen to walk in front of you, science will actually test those phenomena, substituting one for another as variables to determine if changing those variables actually does make a difference. Science, for example, would have a large group of individuals from all different backgrounds, divide them up into random groups, and then assign different color cats to walk in front of them, then follow up with a number of success criteria. If there is a significant difference imparted by a black cat, it’ll be shown in the numbers.

That’s what the intrinsic value of science is- it dispels superstitions and gives us real, accurate knowledge about the world around us. So evolution does the same thing- as a scientific theory, it explains the vast panoply of phenomena seen throughout the biological sciences- as the Russian geneticist Theodosius Dobzhansky noted, “Nothing in biology makes sense except in the light of evolution.” Evolution has tremendous explanatory power- it’s often referred to as the central framework of biological science, and rightly so. In a way, evolutionary theory was an inevitable scientific occurrence, because all the evidence points so strongly to common descent among all organisms. As I mentioned in the Darwin Day podcast, Alfred Wallace was another scientist working at the time who had come to the same conclusions as Darwin. And if neither of them had lived, there would have undoubtedly been another scientist who would have come to the same conclusions. That’s kind of the remarkable thing about Science- the conclusions are eventually inevitable, since they’re based on the facts of reality. At some point in history, Darwin or no, the evidence in Science would have screamed evolution to someone, and now that it has, our knowledge is all the more complete for it.

Now, that being said, I don’t want to leave you with the impression that Science is just about esoteric knowledge about the secrets of this world that are only of interest to ivory-tower scientists who cackle with glee about discoveries about which the average person could care less. Far from it- the explanatory power of evolutionary theory has innumerable practical benefits to each and every one of you, and I’ll try to explain a few today.

First a foremost, evolution helps us to understand a problem that is a growing concern in the field of health-care today. Namely, antibiotic-resistant bacteria. Now, antibiotics have been one of the greatest advances in health care in all of human history. The first, and still the most well-known antibiotic is penicillin. Penicillin works by inhibiting a process in the bacterial cell wall that is necessary to keep the bacteria alive. Essentially, bacteria are always springing leaks as a normal part of their life process, and they’re constantly patching those leaks. With penicillin, those leaks can’t be patched, water pours in, and the bacteria bursts and dies. It’s pretty awesome, actually. And in a perfect world, penicillin would mean that mankind would never have anything to fear from any bacterial infection, ever. But, this is not a perfect world, it’s a world that contains clear biological principles, and evolutionary theory is part of that. What would evolution predict in this situation? The antibiotics introduce a new element to the environment of the bacteria- one that makes it impossible to reproduce. In evolutionary terms, penicillin introduces a selective pressure. That is, all bacteria whose biology is interrupted by penicillin will no longer be able to reproduce, and won’t contribute anything to the species. However, evolution also predicts that due to random variation brought on by mutations and recombination (the latter not so much of a factor in bacteria), some members of a population can respond with greater fitness to any given selective pressure. That is, most bacteria will be killed, but a very few will have a genetic resistance to the antibiotic, and will either reproduce normally, or be able to reproduce at a higher rate than most other bacteria in the population.

So, given these predictions, what should we expect to see? The use of penicillin to kill bacteria will positively select those individual bacteria who are resistant to its mode of action, and they will be able to reproduce at a faster rate than those bacteria which are susceptible to penicillin. Over many generations, the majority of the bacterial population will consist of individuals which are resistant to penicillin, and it will be essentially useless.

And that’s precisely what has happened. Especially in situations where people are prescribed a course of antibiotics, but don’t finish the entire course, bacteria have been selected for throughout the human population which are resistant to many kinds of antibiotics. This means that biomedical research has to work hard to stay one step ahead of resistant pathogens like staphylococcus aureus, or “staph”, which can have deadly consequences if not controlled. And this evolution of resistance isn’t just relevant to health care- in agriculture, insects are becoming resistant to pesticides, also through natural selection.

But the selective pressures can also be used to our advantage. Take, for example, nearly every domesticate animal and plant in use today. Each one was, at one point, an organism very different from what we know today. Take the banana for example- you might think that the banana is a happy coincidence of nature- not so. The banana we eat today is a world apart from the wild banana which was originally domesticated and modified through selection by humans. The original wild banana was a small, tough, starchy fruit with large seeds. Through applied evolution, we now have a large, soft, sweet fruit with no seeds to speak of- even though our ancestors didn’t know what evolution was, they knew how it worked. And the same can be said about dogs, cats, cattle, fowl, corn, blackberries, apples, wheat, and just about everything you put on your table. If it wasn’t for evolution, we’d still be eating, quite literally, twigs and leaves.

Applied evolution is also a potent force in my own field, biomedical research. When investigating new genes, the selection of bacteria is used as a tool to help characterize and understand them. New drugs are discovered through an evolutionary process, in which millions of chemical compounds are sent through a rigorous selective process to see which molecule has the best properties with the least number of side effects. And all results are verified first in non-human animal models, on the evolutionary assumption that mice, rats, and other animals share our biochemical properties because of common ancestry.

The application of evolution even jumps beyond biology. In computer science, genetic algorithms, that is, a programming technique that allows the program to consider a range of possible alternatives and then evaluate them all based on their relative fitness to the problem at hand, is becoming more and more relevant. Evolutionary computing has been used to solve problems in mathematics, molecular biology, robotics, chemistry, and astrophysics.

So, to review, evolutionary theory is a Science, and like the other sciences, exists to examine the nature of reality. That’s its only intrinsic goal and purpose. However, as with all the other sciences, the discoveries of evolution have led to a number of incredibly useful and immensely practical applications that help us to live safer and better lives.

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