Why Evolution Matters (Part 2 of 3)

WHY EVOLUTION MATTERS TO SCIENTISTS (AND WHY SCIENCE MATTERS TO ATHEISTS)


Probably the most heated battle ground in the culture war between secular science and organized religion is the debate surrounding evolution. Why do science-minded people take this theory so seriously? Why are there well-funded organizations (such as the American Association for the Advancement of Science) armed with lawyers, scientists, and educators bent on countering the efforts of creationists and proponents of intelligent design? The simplest answer was penned by Theodosius Dobzhansky in The American Biology Teacher, (1973): “Nothing in biology makes sense except in the light of evolution.” As I have explained in more detail elsewhere, the theory of evolution by natural selection is central to biology. A scientific theory proposes a grand explanation for the way things are and offers hypotheses, which are testable predictions for what we should see if the theory is correct. If the explanation is not testable, it’s not scientific. The theory of evolution is the scientific community’s best effort to explain why there are so many forms of life on earth, why all life is remarkably adapted to its environment, and why different organisms have so much in common.

Let me make a careful distinction here: the term “evolution” simply means “change over time”, whereas “evolution by natural selection” or “Darwinian evolution” is the prevailing theory explaining how evolution occurred. Long before Darwin published On the Origin of Species, it seemed to many naturalists that the relationship between living things looked an awful lot like a big family tree. If you start with, say, your pet cat, it’s clearly a different species than a tiger, but similar enough that you could imagine they have a common ancestor. Stepping back a level from cats, they aren’t really all that different from other 4-legged mammals; they have similar skeletons, the same number of toes, the same internal organs, etc. Now consider all mammals to be one branch of the family tree, with other branches for the reptiles, the birds, the fish, the insects, etc. These branches would all be on a different part of the family tree than the branches for plants and fungi. At the very root of the tree we would find single-celled organisms such as bacteria and yeast, tiny little living things that use the same DNA and amino acids and proteins as all their myriad multi-cellular cousins. At first glance your cat doesn’t seem that similar to cockroach, but viewed in light of the whole of life on Earth, they appear to be cousins in a really big family. The question that scientists ask is WHY? Why does life appear this way? This is what the theory of evolution by natural selection attempts to explain, and it explains life on Earth so well that it is considered by most scientists to be not only the best, but the only explanation. Without the theory of evolution by natural selection, biology has no explanations. Without explanations, scientists get very cranky, because explaining things is what we do. This is why scientists take evolution so seriously.

I am well aware of the objections, even scientific objections, to evolution by natural selection. There are enough people on all sides battling it out elsewhere, so let’s not get into it here. What I want to explore with this post is motivation. I have just explained why scientists take evolution so seriously. You might just as well tell me to explain chemical reactions without orbital theory as ask a biologist to explain life without evolution. But why is evolution important outside of the biology lab? In my last post I explained why Christians think the creation-evolution debate is so important. But what about non-religious folk, so-called secularists? What about atheists? Several of the most prominent leaders of the so-called “New Atheists” movement, such as Richard Dawkins, Jerry Coyne, and P.Z. Meyers, are not only pro-Darwin, they are biologists. Why has evolution by natural selection been a rallying point for the war against religion? I think the explanation is rather simple: the need for explanation.

A popular term among theologians these days is “narrative”. What is the story that you find yourself in? Where did you come from? Why do believe what you believe? In the absence of a faith tradition, the atheist adopts a different narrative. That narrative appears to be science. Science as a philosophical tool presupposes that everything we observe can be explained by natural causes obeying predictable, describable rules of the universe. Science assumes that God, miracles, and the supernatural (including unicorns, faeries, and the Flying Spaghetti Monster) do not exist, not because scientists are themselves non-religious, but because most of the time the world works in an orderly and predictable way without the apparent intervention of the supernatural, and science is a great way to discover the rules underlying the day-to-day functioning of our universe. Atheists have simply taken the next step and decided that science is the best and only way of knowing about everything that there is. The premise that everything we observe is explainable by natural, predictable, and describable causes is no longer a philosophical tool but a simple fact. And who can blame them? Science has been so successful at explaining so much that it’s hard to imagine a role for the supernatural. In a world where we do not see water turned into wine or messiahs raised from the dead, science can explain the origin of life, the behavior of societies, even the chemical basis for the emotions we feel when we have religious experiences. Science as a world-view provides a narrative for those who believe that what we see is what we get: there probably is no God, so stop worrying and get on with your life. Whether the practice of science leads to atheism or atheists have co-opted science as their preferred epistemology is immaterial; it is a fact that if you hang around scientists and science advocates, you’re going to find more folk that don’t believe in any sort of god than those who do, and, in my opinion, it’s not hard to see why.

The theologian Paul Tillich believed that atheists are an unlikely ally of the faithful because they destroy our petty idols. Any god that cannot withstand the scrutiny of the human intellect is no god worth worshipping. As a scientist, I have great respect for the power of the scientific method to explain almost everything we observe in the world. Still, I find science lacking as a narrative, and I believe that the atheist worldview misses out on the fundamental human experience of interacting with the ultimate. But more on that later.

NEXT: WHERE DO WE GO FROM HERE?

Why Evolution Matters (Part 1 of 3)

I participate in a semi-regular gathering called The Alchemists Guild: university students, faculty, clergy, and interested folk discussing faith and science over delicious soup provided by the Lutheran and Episcopalian University chaplains who host us at their student center near campus. The sessions have been moderated by my biologist/priest friend Lucas Mix, and our invited guest speakers have included priests, professors, and students. One such professor, a friend of Lucas’, was an atheist who took the issue of the evolution/creation debate very seriously. He told us that as a science educator, he sees creationism as a threat to good science education, and that as an atheist he is baffled as to why so many Christians find the theory of evolution incompatible with their faith. I’m sure he is not alone in wondering this, and I’m also sure that there are many Christians who cannot understand why he feels so threatened by their belief. In the next three posts I’ll attempt to explain why the issue of evolution comes up more than any other in the conflict between science and Christianity.

WHY EVOLUTION MATTERS TO CHRISTIANS
When I was an undergrad chemistry major at the University of Alaska Fairbanks, a local Baptist church brought Ken Ham and a few of his colleagues to campus for a three-day creation science festival. Most of the talks focused on showing scientific and historical proofs for the Biblical accounts of creation and Noah’s flood as well as poking holes in evolutionary theory, but the single most interesting talk I saw that weekend was entitled “Why Christians find the Creation/Evolution Issue so Important”. In this talk (of which I still have an audio copy that I listen to from time to time) Ken Ham argued very convincingly that accepting an ancient earth and evolution by natural selection is incompatible with Biblical Christianity. He didn’t go so far as to say that if you cannot be a Christian if you believe in evolution – just that your theology is inconsistent and incorrect.

Let me explain why: Self-titled Bible-believing Christians believe that God created the world perfect and without evil or death over the course of six 24-hour days. Humankind was created with free will and initially lived in harmony with God and nature as an immortal being. Humankind lost immortality when Adam and Eve, the progenitors of all humanity, deliberately disobeyed God and ate of the fruit of the tree of the knowledge of good and evil. Their punishment for this disobedience was to be cursed with mortality and pain. The promise given at the time of this judgment was that this curse would someday be overturned by one of their descendents. This descendent would turn out to be Jesus of Nazareth, called the Christ (The Anointed One, or The Messiah). Jesus was the human incarnation of God, born of a virgin impregnated by the Spirit of God. Jesus, having no physical father, was unstained by the hereditary evil that Adam passed on to all his progeny. Jesus lived a sinless life, but was killed by crucifixion despite being innocent of any crime. God accepted the death of the innocent Jesus as the payment for all the sin and evil of all humankind in all history. The Christians that believe this reading of the Bible believe that eternal life awaits all who believe that Jesus is God, is still alive, and will come again someday to judge everyone who has ever lived.

Evolution by natural selection is problematic because it requires death in order to work. Suppose you take the creation story in the book of Genesis as allegorical, that Adam and Eve represent the first hominids to possess intelligence. You could even believe that God breathed an immortal soul into them in an act of supernatural intervention into an otherwise natural process spanning the 3 billion years or so of evolution. But if God used evolution by natural selection to create mankind, then God purposely created death and used death to create. If death was created by God before mankind ever existed and before Adam and Eve ever sinned, then God, not humankind, is responsible for mortality. It is then not clear why God had to come to earth in the form of Jesus and die a sacrificial death to defeat death if death is not the penalty for sin (as is taught in other parts of Christian scripture). This version of the story also casts doubt on the character of God. Why would God use billions of years of evolutionary dead ends, extinctions, predation, and parasitism to create human kind? And why would he create us like we are, imperfect and falling apart from the day we are born? And after all that, why would God blame death on our disobedience?

Some Christians try to be creative with their reading of Genesis to try to make it fit the claims of modern science. What if each of the creation days was actually a very long period of time? That doesn’t really work – not only does the story not really line up with the history of life as told by evolution, but plants get created on day three and the sun doesn’t get created until day four. Light gets created on the first day, but how could there be light and no sun? You could say that the light emanated from God himself, but now we have a mixture of natural and supernatural causes and it’s unclear which type of cause is the best explanation for which part of natural history.

This unwieldy mixture of natural and supernatural really is the problem in the end. The Bible-based theology outlined above is based on the simple belief that the Bible is the infallible words of God. Once that is accepted, the rest of the story is the clear, logical, and internally consistent result of a literal reading of the Bible. As soon as one attempts to call any part of the Bible allegorical or not literally true, it is difficult if not impossible to objectively decide where to stop. What about Noah’s flood? God’s constant miraculous intervention on behalf of the Israelites? The miracles and resurrection of Jesus? It calls into question why one would continue to hold on to beliefs that had their genesis in Genesis if one is willing to dismiss any part of their belief system that comes into conflict with the findings of modern science.

When I first heard Ken Ham explain that it is not possible to be a consistent, Bible-believing Christian and still accept evolution by natural selection, I felt forced to immediately agree with him. But my agreeing with him did not have the effect I imagine he was going for. If I could not be both an evolutionist and a Christian, I decided, then I must not be a Christian. I’ve since changed my mind on that issue, but I’ll deal with that in part three of this series.

NEXT: WHY EVOLUTION MATTERS TO SCIENTISTS (AND WHY SCIENCE MATTERS TO ATHEISTS).

Happy Birthday Chuck

Today is the 200th anniversary of the birth of one Charles Darwin, a would-be-cleric-turned-naturalist whose seminal work On The Origin of Species turned the study of nature into a science. Although Darwin was by no means the first to propose that all life descended from a common ancestor, and although his theory of evolution by natural selection has been challenged and augmented since its initial publication in 1859, his name remains synonymous with evolution because his was the first and most enduring theory to propose a solidly scientific explanation for the remarkable diversity of life on Earth.

Let me explain what I mean when I say that the theory of evolution made biology a science. The scientific use of the word theory is very different from the colloquial use. You might casually say that you have a theory about why your friend is late for your movie date or why your car is making a funny noise. In this usage, “theory” means “guess” or “conjecture”. Not so a scientific theory. According to the U.S. National Academy of Sciences, “the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena.” The cause of gravity, the wave and/or particle nature of light, relativity – these are scientific theories, treated as fact. A scientific theory has a very important defining characteristic: the ability to make predictions. The rigorous testing of the predictions made by a theory is science. Prior to the theory of evolution, biology was basically the practice of collecting and cataloging Earth’s life forms. Naturalists could tell us what sorts of species were out there, but not why there were species. Think about it. Why should there be species at all? Why does every species seem to be uniquely adapted to its environment? Why do some species thrive while others don’t? Why are there fossils of strange creatures that don’t exist anymore? Scientists are able to answer questions like these with the theory of evolution by natural selection.

I doubt that you could find anyone in the English-speaking world who has never heard of evolution, but I doubt that many of them could explain what Darwin’s theory actually claims. For their benefit, I present to you here the truncated version (with many thanks to my professor Eduardo Wilner for his insightful classes on evolutionary theory and philosophy of biology).

• Observed: Living things reproduce, and when they reproduce they tend to make more than one offspring. If this were not the case, their species would die out as a matter of simple arithmetic.
• Observed: Resources are limited. The planet is finite in size. Even if there were only one type of reproducing animal and only one type of food, the planet would eventually be overrun.
• Observed: Animals will die.
• Conclusion: Given limited resources, staying alive is a competition. If one animal is more suited to staying alive than another, it will outlive its competitor (this is what we call fitness).
• Observed: Offspring tend to resemble their parents.
• Conclusion: There must be some manner in which the traits of the parent are passed on to the offspring. (Keep in mind that Darwin wrote “On the Origin of Species” before Mendel’s discovery of genes had been published, and nearly a century before Watson, Crick, and Franklin elucidated the structure of DNA).
• Conclusion: More animals that are fit will live to reproduce than will less fit animals. The traits of surviving animals, including traits of fitness, will be passed on to their offspring. Eventually, these traits of fitness will become widespread in a population and less fit traits will disappear.
• Observation (and this one’s the clincher): Creatures change with time. Darwin didn’t know about DNA or genes or mutation, but he observed (as other naturalists had been observing for centuries) that creatures are remarkably capable of changing with their environment, and that entirely new traits can spring into existence. He proposed that their must be random changes in creatures and that these changes can be passed on to offspring (that they are heritable).
• Conclusion: Changes that increase fitness will be retained; changes that decrease fitness will be weeded out. Over time, this will give rise to creatures that don’t resemble each other at all, even though they descended from the same ancestor.

So there you have it: evolution by natural selection can be summed up as heritable variation in fitness.

How does evolution by natural selection hold up as a scientific theory? Let’s look at the criteria:

• Does it explain the world around us? Yes. It offers a plausible explanation for why there are many different types of life on earth, and why each type of creature is remarkably adapted to its environment.
• Does it make predictions? Yes. Since the whole theory is based on logical conclusions drawn from observations, we can draw further conclusions that should be true and check whether these conclusions hold up with what we see in the world.
• Are the predictions testable? Yes. For example: if all life on earth has a common ancestor, we would expect to see common traits present in distinct species. Do we observe this? Certainly. Mammals from mice to bats to whales to people have remarkably similar skeletons (i.e. fingers and toes). All life on earth uses the same 4 molecules to make up their DNA. There is remarkable similarity in the DNA codes for making proteins, and there is often further similarity between species in the sequence and structure of specialized proteins.

An important point here: nothing can ever be proven in science. Every time an observation matches a prediction, we say that the hypothesis (and thus the theory) has been supported. If the observation does not match the hypothesis, then the hypothesis is proved wrong. If hypotheses are disproved enough times, one should begin to doubt the theory. If, however, hypothesis after hypothesis and prediction after prediction are supported by the observations, the theory grows in strength until it is accepted as practical fact.

I am well aware that many people do not find Darwin’s story compelling; some find it downright offensive. Future posts will discuss why that is. But in honor of Darwin’s birthday, I give you the above with the hopes that you will think twice before ever saying “Evolution is just a theory”.

Update:
Many other bloggers wrote articles in honor of Darwin day. Here is one of my favorites from SEED Magazine