The Prism and the Rainbow: A Christian Explains Why Evolution Is Not a Threat

7. What Is Evolution?

47 The fruit of the righteous is a tree of life. proverbs 11:30 Everything is simpler than you think and at the same time more complex than you imagine. johann wolfgang von goethe e volutionary biology is the study of the history of life on Earth and of the processes that have led to life’s diversity. It’s one of the biological sciences. And yet it’s also more than just “one of the biological sciences” in that it gives us a broad, general framework that unites the biological sciences. Fields of study as diverse as physiology , behavior, ecology, genetics, biochemistry, medicine, and more are all supported by, and linked by, an understanding of evolutionary theory.1 Furthermore, a better understanding of evolutionary theory is critical to our survival. If ever we are to solve such problems as the spread of HIV, SARS, avian and swine (H1N1) flu, and other rapidly What Is Evolution? 7 the prism and the rainbow 48 evolving infectious diseases, if ever we are to gain the upper hand on genetically inherited disorders, it will be because we have gained an understanding of how such maladies arose and have changed, and are continuing to change, over time. The main concepts of evolution can be summarized fairly simply. The following description (with only slight modifications) comes from the “Evolution 101” section of the web site “Understanding Evolution,” a joint project of the University of California Museum of Paleontology and the National Center for Science Education: Biological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations). Yet biological evolution is not simply a matter of change over time. Lots of things change over time: trees lose their leaves, and mountain ranges rise and erode. But these things aren’t examples of biological evolution because they don’t involve descent through genetic inheritance. The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother. Through the process of descent with modification, life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Evolution means that we’re all distant cousins: humans and oak trees, hummingbirds and whales. Thus, the central idea of evolution is that we share common ancestors. We are descended from these ancestors, but modifications have arisen along the way. “Descent with modification,” perhaps the simplest and most often used “thumbnail” definition of evolution, simply means that over time, from one generation to the following generations, slight changes accrue in a population. We descend from our grandparents, 49 What Is Evolution? as they did from theirs. But we are not identical to them. And it is the same in all organisms. One of the cornerstones of evolutionary theory is natural selection , an idea that can be expressed in five simple statements: 1. There is a lot of variation in nature. Individual organisms in a population—whether trees, rabbits, or bacteria—are not identical. 2. In nature, organisms tend to produce far more offspring than can survive, something particularly obvious in plants and insects. Some produce hundreds of eggs or seeds; some produce many millions. 3. Not all of these eggs and seeds will make it. Some will survive and some will not. 4. The individuals that possess traits that are most useful in the environment in which they find themselves are the ones most likely to survive and (more importantly) pass on their genes to the next generation. 5. Over time,2 the population changes as some traits are preserved and others are eliminated , such that future populations will differ from earlier ones. HumansknewforhundredsofyearsbeforeanyofDarwin’swritings that plants and animals could be intentionally bred so that certain traits werepreserved,andotherseliminated,inthenextgeneration.Wedothis routinely today (as we did way back then) with domestic farm animals, pets, crops, flowers, microbes, and many other organisms to “artificially select” the traits we want to see in the next generation. It’s how breeds of dogs and cats are created (and maintained), how we make cattle that produce more milk or more beef, how we create fruits without seeds. In a sense, the discovery of “natural selection” was simply the recognition...