Evolution

If someone asked me if I was a creationist, I would say yes. The problem with this answer is that the two groups (religious folks and scientists) that often ask this question use it as a litmus test. My answer hardly works because neither side has any idea what I’m really talking about. The word creationist, in my west Texas culture, often refers to how you interpret early Genesis. When people ask “Are you a creationist?” what they’re really asking is “You think evolution is a bunch of hooey, right?”. Likewise, in many scientific circles, the word has a horrible connotation. It instantly brands someone as a zeolot, incapable of rational thought and discourse, someone who could never look at the world around them and follow the evidence. I like to label myself as an evolutionary creationist. This goes back to the difference between science and faith that I discussed a few days earlier. Who (creator God), how (evolution).

I still remember the first time that I realized evolution happens. I was 16 years old and on a birding tour in southeast Arizona. I’d just purchased a copy of an excellent field guide to Mexican birds. I was flipping through the pages, astonished at the diversity before my eyes when I came across this.

From Howell and Webb, plate 25.

These are the pygmy owls — small owls that hunt birds by day. (Note that six species are illustrated.) The US gets a couple of species, but things get a little more complicated as you move south. They have the subtlest of differences visually, occupy different habitats, and “sing” (a series of monotone whistles) with slight differences between the populations. I was reading about them and noticed that there were many confusing issues surrounding their classification. The number of species recognized was not universally agreed upon. I asked one our leaders, a middle-aged guy who knew a lot more about birds than I did, “why don’t scientists know if they’re seperate species?” His answer was, “because they’re still evolving.” For the first time, I realized there was a reason things in nature were a certain way. Science had the ability to explain what I was seeing in the world around me. Over the years, my pygmy-owl experience has happened thousands of times.

I’m literally overwhelmed with the idea of writing a post about evolution. If 1000 page textbooks are written on the subject, what can I add with one post? In addition, I came to my understanding over many years of experience with the natural world and with plenty of time to reflect on the subject. I’m now trying to condense all that into one post in which you’ll read in less than an hour.

In spring of 2005, I gave a four Wednesday night bibleclass lessons at church on

1. How should we intrepret early Genesis?
2. What is a Christian view on nature and the environment?
3. What is science, who was Darwin, and how has the church responded to and viewed evolutionary theory over the years?
4. The theory of evolution

I had some incredible help with the first three lessons. A couple of bible professors at Abilene Christian University lent their expertise while a biochemistry professor and an about-to-be doctorate student in physics helped me talk about science. The fourth lesson was all mine though. I spoke about evolution, explaining what the theory is and isn’t as best a person with a bachelor’s degree in biology can do. I prepared myself for the worst, yet the response was overwhelmingly positive. In this post, I’m going to run through that lesson again (lot’s of pictures ahead!). If you already have a good understanding of evolutionary theory, you may find this quite basic or simplistic. If you’ve never learned much about it though, you may be surprised by some of what’s ahead. I’ll also point to some resources that may help you as you reflect on this issue. My whole point in doing this is that I know some friends and family may be quite uncomfortable with the theory and its compatibility with a Christian worldview. Since I plan on making a career as a scientist, I wanted to give a glimpse of where I’m coming from.

I must give you one slight warning. This post is very long. The problem was that there were two options in discussing evolution. I could either tell you that it was a great theory and that you should all take my word for it, or I could actually try to give a simplified explanation on how the theory was formed and where our evidence for it comes from. I choose the latter. I also wish to make a plea with any Christian readers who are opposed to the theory. If you aren’t willing to take the time to read this information (though long and boring it may be), you really don’t have a right to form an opinion. Think about it this way. If I have never studied anything about music theory and have never listened to Mozart or his contemporaries, what right do I have to speak with authority on his music? In that light, I greatly plead with Christians to either take some time to consider what the science has to say, or respectfully tell yourself and others, “I don’t have any knowledge on that subject”.

If you only have time for one book

Before I go any further, I’m going to point to a reference. If evolutionary biology troubles you, I’ve got a book I’d like you to read. Biology Through the Eyes of Faith, by Richard Wright. You don’t even have to read the whole thing. I’d specifically recommend chapters 3, 4, 5, 7, and 8. For those really impatient, chapters 5, 7, and 8 will cover the topic of Genesis and the theory of evolution, while leaving out an overview of the philosophy behind science. This is the book I’ve suggested for several people close to me (one being my wife) that had questions, and all of them have come away saying it was very helpful and well written.

I will now go through and reproduce my lesson on the theory of evolution I gave in April of 2004 at church. I think this will be about as good as I can do to talk about the theory, and I’ll point you to different references along the way for further reading.

How evolution came to be a theory

Charles Darwin

When the word evolution comes up, most of us associate it with Charles Darwin (more information here as well). What may not be as well known is that Darwin wasn’t the only person to come up with the idea that species change over time or even his ideas on how they change.

Jean-Baptiste Lamarck was an earlier scientist who proprosed that species change over time, though his ideas are now widely discredited. He believed organisms acquire traits by using them, and lose others through disuse, in their own lifetime. These are then passed down to future offspring. So to explain how a giraffe got a long neck, for example, Lamarck’s theory would suggest that an earlier ancestor to a giraffe stretched its neck to reach higher branches, thereby increasing the length of its neck. Its neck length was then passed down to its offspring, who stretched their necks to reach higher branches. As I said, this view is not accepted by current scientists, and Lamark’s name has become synonymous with his discredited theory.

Charles Darwin on the the other hand proposed that organisms changed over time through a process called natural selection. Before discussing natural selection, it’s worth noting that Darwin was not alone in his formation of this hypothesis. What follows is the fascinating story of Alfred Russel Wallace.

Darwin, well aware of the fact that his ideas would cause a ripple through Victorian England society, had been working on his theory for some 20 years, without making his ideas known outside close family and friends. He corresponded to many people around the globe, one of them being Alfred Russel Wallace, who was then studying the natural world in the Malay Archipelago. When Wallace sent him a manuscript of a paper he was considering for publication, Darwin realized that Wallace was about to beat him to the punch on the theory of evolution by natural selection. Two of Darwin’s friends presented Wallace’s findings on July 1, 1858 to the Linnean Society of London, along with Darwin’s own work, giving Darwin’s ideas the priority over Wallace’s.

Here’s my own take on this series of events. First, it was truthful. Darwin had been working on the ideas much longer than Wallace. It’s only fair that he gets the credit and recognition for it. Secondly, though Wallace could have been upset, he actually was pleased with the outcome. Darwin was better known in scientific circles of the day, and Wallace felt that his ideas were better received and accepted coming with the backing from a scientist with Darwin’s reputation. Finally, I think it is extremely cool (to use the vernacular of my day) that the idea of evolution by natural selection came about independently from two people, based on their observations of the natural world around them. This is much the same as calculus, being independently formulated by Isaac Newton and Gottfried Leibniz.

A proper understanding of natural selection is crucial in understanding evolution

At the foundation of biology’s theory of evolution is the theory of national selection. Here is a modern day definition of natural selection I used in my lesson at church.

Natural Selection — The theory by which organisms in nature better suited for their environment are more likely to pass on their genetic code through their offspring than those organisms less suited to their environment.

Darwin’s ideas in part came from the breeding of pigeons, something he fancied greatly. He noted that people could produce impressive changes within a species by carefully controlling the breeding of the animals (artificial selection), and he wondered if nature, over time, could do the same thing (natural selection).

Here are some examples of artifical selection in action.

Three pigeons: Indian Fantail (from left), Jacobin, and Voorburg Cropper.

Here’s a couple of examples from the feline world with a persian and a sphynx.

And finally examples from the dog world. From the wolf, we’ve produced dogs as big as great danes and as small as chihuahuas.

Note that in all three sets of pictures, scientists consider these animals to be the same species. Man, in no more than a few thousand years (and in some cases much less) has produced this variation by controling their breeding.

Natural selection starts with the inherent variability in organisms

If you measure any given characteristic for a population of any given species, you’ll typically find a bell curve, such as the one pictured below. This holds true for height in people, bill thickness in birds, and gill length in fish. What this means is that most of the individuals in a population are going to fall in the middle of the extremes, while some individuals will be on one extreme or another for a measurement of a given trait.

In his day, Darwin did not understand where this variability came from. He writes to a friend, Thomas Huxley,

You have most cleverly hit on one point, which has greatly troubled me …what the devil determines each particular variation? What makes a tuft of feathers come on a cock’s head, or moss on a moss-rose?

Our ignorance of the laws of variation is profound. Not in one case out of a hundred can we pretend to assign any reason why this or that part has varied.

At the same time Darwin was conducting his work, another biologist who is now extremely famous for his discoveries was at work. Gregor Mendel, an Austrian monk, discovered the principles of heredity and is often known as the father of genetics. He published his work in 1865 in an obscure journal where it went largely unnoticed until its rediscovery some 35 years later.

In the earlier part of the 20th century, scientists advanced our knowledge about DNA and chromosomes and established that our hereditary traits come from our chromosomes. Finally in the mid 1950’s, James Watson and Francis Crick nailed down the structure of DNA itself and shortly after the birth of molecular biology was realized. (For a fascinating if somewhat techinical overview of these discoveries, see the history of DNA at Wikipedia.)

The point to all of this is that we know now where these variations come from. The genetic code, the blueprint for every organism living on earth, is responsible for the variation of characteristics that we see in nature.

A nice study that shows all of this at work

A great way to really explain what I’ve spent so much effort going over above is to show it in action, in the natural world. A very famous evolutionary study by a couple named Peter and Rosemary Grant has been carried on since 1973 on the Galapagos Islands.

Medium Ground Finch (Geospiza fortis)

In particular, they focused on the Medium Ground Finch (Geospiza fortis) on the island of Daphne Major. The nearby island of Pinta has fortis with beaks that average 1 millimeter thicker than those on Daphne Major. The seeds of torchwood trees, a food source for the birds, are the same size on each island. The Grants have observed fortis on Daphne Major take as long as 6 minutes to crack a single seed, and most give up after a while without success. On the island of Pinta however, 4 out of 5 fortis can crack the seeds with minimal effort. That’s the difference a single millimeter makes! Turns out that in a drought, that can be the difference between life and death.

In 1977, there were 1,200 fortis on Daphne Major at the beginning of the year which marked a horrible drought. By the end of the year, the drought left only 180 birds alive, an 85% mortality rate. The Grants were there every step of the way, taking constant measurements. They found that pre-drought, the average bill was 10.68mm long and 9.42mm thick. After the drought, the average bill was 11.07mm long and 9.96mm deep. The drought selected those birds with larger bills. In effect, it moved the bell curve for bill size to the right. I found this graph on the web which shows this concept. (Notice the numbers are a little different — I’m guessing due to the time they were taken — but the principle is still the same).

One consequence of this shift was a skewing of the sex ratio. At the start of the drought, there were about 600 males and 600 females. At the end of the drought, 150 males (which average 5% larger) survived but only 30 females. The reason was food. Smaller seeds were eaten up quickly during the drought, leaving only the larger, thicker skinned seeds as food. Only birds with larger bills could get to the food necessary to survive.

Sexual selection (more on that in a minute) pushed the birds towards larger bills still. As the females paired off to mate with males, the Grants documented that only 1 in 5 males got to mate. Females chose males with the largest bills. It’s easy to see how the genes that account for those larger bills become more prevelent in a population after the drought than they were before.

One of the things that surprised the Grants was the speed with which these changes were taking place. It was always assumed that evolution happened very slowly. In fact, when they started their study, they probably didn’t know what to expect. At this rate of change, fortis was about to evolve right in front of their eyes. It hardly seemed logical.

December of 1982 marked the beginning of the wettest year in the history of the islands. The El Niño was probably the strongest of the 20th century. Total seed mass on the island increased by over 12 times from the previous year. Big seeds actually became scarce, as the plants that grow them were out competed by plants with smaller seeds. The year before, females hadn’t bred successfully. Not a single offspring was fledged. That would change in 1983 when 40 eggs were laid and 25 young fledged. In this newfound lush paradise, birds with large bills (which also have larger bodies) couldn’t get food as successfully as birds with smaller bills. Natural selection began to swing in the opposite direction. All told, even after swinging back the opposite direction during the floods, the finches still retained a net increase in the size of their bills.

This helped science develop a new understanding of natural selection. It can pull populations back and forth as the environment changes, selecting traits that best suit an individual for its habitat’s current conditions.

My knowledge of the Grants studies, and others like theirs, comes from the excellent book Beak of the Finch by Jonathan Weiner. I’d highly recommend it for those that wish to read more on the experiments and studies that have confirmed and aided in our understanding of evolution and natural selection.

Different types of selection shape species

There are several different types of selection that can shape populations. What the Grants witnessed is called directional selection. In it, the bell curve for a given characteristic shifts to the right or to the left. Another way of stating this is that a character in a population is selected for or selected against. With the finches, we would say that large bill sizes were selected for, while small bill sizes were selected against.

Here’s a graph of directional selection at work.

Another type of selection is called stabilizing selection. In this type of selection, both ends of the bell curve are selected against. A guy named Jamie Smith studied Song Sparrows (Melospiza melodia) on Mandarte Island in British Columbia, looking for the exact kinds of things the Grants had observed on the Galapagos. After years of study, Smith was going to report that no natural selection was taking place in Song Sparrows on Mandarte. However, a friend realized that he’d been looking for the wrong thing. His data actually showed that natural selection was ruthlessly weeding out those birds at either end of the bell curve. It was selecting for the middle.

Here’s a graph illustrating stabilizing selection.

A third type of selection is called disruptive selection (or sometimes bimodal selection). It selects for either end of a bell curve. From my understanding, I would say that disruptive selection is observed less frequently in nature than the other two types. It is perhaps easiest to explain with a hypothetical example. Say you had a population of rabbits. Their fur ranged from white at one extreme to black at the other. Most of the rabbits were gray. Now say you placed this population on the side of a mountain that had either black volcanic rocks or snow. What would happen is that gray fur would be selected against as predators would catch gray rabbits with greater frequency than black rabbits (on black volcanic rocks) or white rabbits on snow.

We do observe examples of disruptive selection in nature though. The soils around mines for example often become polluted with heavy metals in which most plants cannot grow. There are grasses however that are able to spread from non-contaminated areas to grow in these soils. As these plants develop resistance to these toxic metals, they become less and less fit to grow on uncontaminated soils. Because grasses are pollinated by the wind, both resistant types and nonresistant types continue to breed which each other. Disruptive selection has been identified as being at work because both less resistant grasses growing on contaminated soil and more resistant grasses growing on uncontaminated soil experience higher mortality rates than the ancestral populations from which they came.

Here’s an illustration of disruptive selection.

Sexual selection also shapes species

Another force that works much like natural selection is sexual selection. Rather than nature driving the bell curve, members of the opposite sex and how they choose their mates play a deciding factor in the evolution of species.

guppy

A famous study on sexual selection involved John Endler and the guppies of northeast South America. These particular guppies have a maximum of 7 natural predators. Six are fish, while 1 is a freshwater prawn (a type of shrimp). They live in mountain streams, and as you move lower in elevation, the number of guppy predators present increases. Waterfalls typically keep predators and guppies isolated within their populations. In effect, the fish are on “islands,” preventing from breeding with one another, just like the finches of the Galapagos.

Endler discovered that males have an order to their spots, even though they look chaotic to the human eye. The more predators in the stream, the smaller and fainter their spots. The less predators, the larger and brighter their spots. Even more interesting, in a few of the head waters where the only predators present were prawn, Endler noticed that male guppies had large red spots and rather than blue.

The explanation is a tug of war between natural and sexual selection. The more predators present, natural selection favors smaller and fainter spotted Guppies. However, females will choose males with larger and gaudier spots. This is sexual selection. As for the areas where only prawn existed, they are color blind to red, thus the interplay between natural and sexual selection produced guppies with large red spots.

Endler also carried his observations back to the lab. He set up experiments, breeding guppy stocks over many generations to a heterogeneous mixture of spots and then put them in mixed environments with varying levels of predators. Over their subsequent generations, he watched the same results he observed in the wild come back in the lab. The spots on male guppies with no predators became bolder and bolder, while guppies with high rates of predators became more and more camouflaged.

So what we’ve learned is that natural selection isn’t the only force at work in nature. Sexual selection can often push species in the opposite direction from natural selection, and play a vital role in the evolution of species.

So how did a giraffe get its neck?

Remember my example of how Lamarck’s theory would have explained the neck of a giraffe? Well now that we’ve had an overview of natural selection and how it works, let’s look at how it differs from Lamarck’s theory in explaining the neck of a giraffe. Rather than a giraffe individual stretching its neck to reach the trees, our current understanding says that animals are born with variable features (the bell curve examples from above). The early ancestors to modern giraffes experienced a selection for longer neck size. They were able to reach food sources that weren’t being used by other competitors, so they reproduced better than those in the population with shorter necks. Over many generations of selecting for longer necked individuals, you can end up with a giraffe. (Note that I’m not trying to share something earth shattering about giraffe evolution. The fact is, I’ve never studied giraffes and don’t know much about them. Rather on a very simple level, I’m pointing out the differences between Lamarck’s theory and our current understanding).

Some further information to clarify natural selection and evolution in general.

1. Natural selection is tied to reproduction! A disease that kills you before you can reach sexual maturity would be strongly selected against. However, diseases which strike in old age (like cancer often does), have no effect on the reproductive abilities of a species and thus are not selected against.
2. Natural selection is not “natural perfection.” Here’s something utterly fascinating which you may not know. Sickle cell anemia is a disease that affects our red blood cells. One would think that it would be selected against, as it would seem to put anyone with it at a reproduce disadvantage. However, it is the most common genetic disorder amoung African Americans, with 1 in 12 being a carrier. As it turns out, evolution explains why this happens. Due to the biology of the parasite that causes malaria, people who are carriers of the genes for sickle cell anemia are 10 times less likely to contract Malaria! Natural selection does indeed select against sickle cell anemia for people who live in areas where malaria does not occur. In places where malaria does occur however, natural selection favors the sickle cell genes, up to a point. Being a carrier is advantageous, though if two carriers reproduce, their children will have a 1 in 4 chance of being stricken with the disease. (I’m simplifying this a little because the biology is very complex, and I don’t even know all the ins and outs.)
3. The variability that we see in the genetic code of organisms comes through mutations. This is a subject that’s far too complicated for me to discuss now — and honestly — I have much to learn about the subject myself. We have however learned of many ways in which mutations occur. The information found at that link is mostly over my head (I’ve never been as interested in genetics as ecology), but I’ve pointed it out because science isn’t just assuming that mutations take place. Rather they’ve documented them well and are constantly digging deeper, learning more about how they work. An example of just how a mutation can have a big effect can be found in our sickle cell anemia discussion above. Sickle cell anemia is caused by the mutation of one point of DNA, where a GAG changes to GTG in the ß-globin gene. That very small change was responsible for the sickle cell anemia gene showing up in the human population.
4. Speaking of mutations, it is worth noting that things aren’t always what they seem. Sometimes small changes to the genetic code may result in big changes. For example, we’ve recently learned that a very small number of genes is involved in deciding the form and function of the many body shapes and patterns we see in animals. This relatively new field, called evolutionary developmental biology (or evo-devo for short) has opened our eyes to the fact that sometimes radical changes to shape or function may not have required extensive mutations. To put that in English, a small mutation may have been responsible for taking an organism with four limbs and giving it six or eight.
5. Another point to briefly hit upon is the idea of a niche and competition. A niche is a species’ role or place within its environment. Basically, species do not share the exact same niche. Nor will a species evolve into a niche which is already occupied. Competition between species (not just within) can place limits on how things evolve.
6. Another point worth mentioning is that isolation greatly speeds up evolution. It’s why islands are hotbeds of evolution. Populations that get stranded on an island have natural selection act upon them in different ways from their ancestral populations. Likewise, islands need not be geographic. They can come from any barrier which keeps species from breeding together, such as the waterfalls in the guppies habitat, or the timing of reproduction between plants. If something places a barrier between the reproduction of two populations, different mutations will arise in those populations and those mutations will respond differently to pressures of natural selection. On the other hand, evolution can move much slower when large populations with lots of inbreeding occur. That’s because genetic information gets shared thoroughout the population as breeding happens.

Micro vs. Macro Evolution

I’ve spent an enormous amount of time discussing the principles above because they are believed to be the driving force behind evolution and account for the diversity that we see today. However, is has become common for many critics to accept so-called “micro evolution” — the idea that species change slightly due to the mechanisms of natural or sexual selection — while rejecting that these mechanisms can account for the larger diversity that we see in the natural world. For those interested in a very thorough explanation of our understanding of macro-evolution, take a look at this prepared material at Talk Origins. The truth is that distinctions between macro and micro evolution are rather arbitrary and ill-advised. Acting as if “micro” evolution is good science but “macro” evolution is not well supported is disingenuous. I’m going to briefly run through some things that evolution beautifully explains. These are large scale issues, and would be considered more along the lines of “macro” evolution.

Adaptive Radiations

Adapative radiations are the result of one or several species rapidly evolving to fill a niche. Darwin’s finches are just such an example. Though many species fall within the typical finch niche (seed eating), one species uses a cactus spine to get at resources in crevices like a woodpecker (no woodpeckers are present on the Galapagos), another has a very thin bill and fills the niche of a warbler, while still another pulls feathers from the legs of larger birds and drinks the blood.

On the islands of Hawaii, we see the greatest diversity of fruit flies (genus Drosophila). Males dance with incredibly sensitive precision to mate with females of their own species. If the male gets the dance wrong by even the slightest amount, the female will not mate with him. This example of sexual selection has helped the flies evolve into the many species they are today. Scientists conducted an experiment with Drosophila subobscura and discovered that after 14 generations bred in complete darkness, the males no longer dance and will feel their way around to find a female and then try to force mating. James Shreeve, the scientist conducting the experiment remarked,

It takes just fourteen generations to turn a Drosophila subobscura from a courtly dancer to a blind, tapping rapist.

Funny as that quote is, evolution explains why we see these patterns of adaptive radiations in nature.

Genetic similarities

Analysis of genetic codes many times confirm previous relationships between groups and other times sheds new light on our previous understandings. We see amazing patterns in the genetic makeup of organisms and can use it as a tool to better understand the evolutionary relationships in nature. We are also using this information to probe our own genetics and compare it to other species in search of the causes of genetic diseases and their solutions. Here’s a safe prediction of my own — evolutionary biology will become increasingly important to advances made in medicine in the years ahead.

Biogeography

Closely related species tend to be clustered together. For example, South America shares two species of rheas (large flightless birds), not Ostriches as in Africa or Emus as in Australia. And speaking of Australia, it has very few placental mammals and is instead filled with marsupials. (Marsupials came first, and were replaced by placental mammals, but by that time, Australia had become isolated enough to protect it’s marsupials).

Nasikabatrachus sahyadrensis

Here’s another example. Meet Nasikabatrachus sahyadrensis. (Note that Ocellated accepts no responsibility for any injuries that may result from trying to pronounce that name). This purple frog made waves when it was discovered by science in 2003. It is placed in its own family (the Nasikabatrachidae) which is related to more primitive frogs known from the fossil record. It also was the first new family of frogs described since 1926! (Note that a family refers to a taxonomic classification, as in that whole Kingdom, Phylum, Class, Order, Family, Genus, Species thing you learned and forgot in high school). Also interesting is that its closest living relatives were another group of primitive frogs in the family Sooglossidae. Now the problem is that the Sooglossids are found on the Seychelle Islands near Madagascar, while the Nasikabatrachids are found in the Western Ghat mountains of India. (See this map). This is quite a distance apart. If we envision these animals evolving from a common ancestor, how did they get their current distribution? The answer involves the earth’s geography at the time these frogs evolved. Pictured below is a map from the late Cretaceous, around 100 million years ago, when these two frogs families diverged from one another. Notice that the Seychelles, Madagascar, and India were all joined together as one land mass.

Evolution and the earth’s past geography also explains similarties we see between South America and Australia. For example, platypus fossils are found not only in Australia but also South America. South America also has the second highest number of marsupial species after Australia. Why is this so? The answer is that during the Cretaceous, Australia and South America were linked by Antartica.

The distrubtion of species around the globe isn’t just random. Evolution gives us an understanding of why we see these patterns of distribution.

Morphology (shape and function)

We also see overwhelming evidence for evolution when we look at the shape and function of features in the animal kingdom.

• When it comes to wings, why do bats use skin, birds use feathers, insects use their cuticle, and “flying” fish modified fins?
• Why do some snakes have rudimentary legs?
• Why do species of flightless beetles and flies have wings?
• Why do alligators and crocodiles have vastily more in common with birds that other reptiles like lizards? (Crocodilians have four chambered hearts, build and guard nests, vocalize to their young, have gizzards, etc. These are all bird like features which other reptiles do not share.)

Evolution gives answers to all these questions.

The fossil record

While some would criticize the fossil record for being incomplete or having gaps, this should not suprise us when we consider the extremely difficult conditions under which fossils are preserved. There are amazing and informative fossils that shed much light on evolution. Even when relationships between groups are hard to determine, the fact that fossils tell us that life has changed dramatically over time is overwhelming evidence for evolution and is the basis by which many scientists refer to evolution as both fact and theory.

Archaeopteryx

Consider Archaeopteryx (pictured at right), perhaps the most famous fossil ever. Archaeopteryx is believed to have evolved from the same dinosaurs that gave rise to birds. However, it’s not considered to be a direct ancestor of modern birds, having gone extinct without leaving any current ancestors. Its features are a mix of dinosaurian and avain characteristics. Its feathers are much like modern birds, though most of its other characteristics are more dinosaurian. Creationists that dismiss evolution have gone to great lengths trying to argue the interpretation of this fossil. Rather than double the length of this thread going into this highly technical discussion, I’ll just leave it to the reader to answer… Regardless of Archaeopteryx’s place within dinosaur–bird evolution, does a little dinosaur with bird feathers strengthen or weaken the evidence that life has changed over time?

There are many other examples worth pointing out. In particular, here’s a link that gives good (though quite technical) information about several series of transitional fossils which have greatly aided in our understanding of evolution in certain areas, human origins being one of them.

Once again, evolution explains why we have a fossil record and why throughout time, since the beginning of life on earth, the composition of species has undergone repeated change.

Final Remarks and Reflection on Faith

I’d like to add a final remark about evolutionary theory. Evolution is often presented by critics as being a theory in peril. Scientists are abandoning it in droves or grasping at straws to support it, we’re told. If you walk away with anything from this post, know that this is entirely untrue. Whoever says this is either terribly misinformed, or worse, purposefully lying. Evolution explains the data around us better than any other explanation we have and has stood rigorous testing from the scientific community for close to 150 years. It is overwhelmingly accepted by biologists in all fields, and is undoubtedly one of the most influential and important theories in all of biology.

I hope I’ve given you something to reflect on, and illuminated your understanding of evolution by natural selection. I really don’t think evolutionary biology need strike fear in a Christian’s heart. If we hold that God created the earth and everything in it, why should we be scared to study it and enjoy what it reveals to us?

Furthermore, there is wonder and beauty to be found in the understanding that evolution gives us about the natural world. God’s creation was not just stagnant, incapable of responding to its environment. Rather His creation is gifted with the ability to change in a changing world. In this way he not only created, but is constantly creating, even today.

I’ll offer to you what a biology professor of mine at Abilene Christian offered to his class as we studied this subject, many for the first time. Perhaps more than anything else, pride is what causes us to reject evolution. We view ourselves as so superior to the rest of creation that it insults us to think we have anything to do with God’s other creatures. Pride has always been a problem in our fallen state though. There is much good to be found in the idea that we too are a part of creation. Indeed much of our creation was done before we even showed up. This understanding offers a well connected view of life and gives a much more balanced view of our place in creation. We are a part of creation. A part which God was pleased to bestow his image upon.

What comes next?

My last post in this series on science and faith will be about Intelligent Design. Many Christians seem to have placed great hope that this alternative to evolution can save their faith and restore God as the creator of the universe. I definitely need to give an explanation on the implications of Intelligent Design, from the viewpoint of science and my own faith as a Christian. Not that this will come as a surprise, but I am extremely troubled by it and the way in which many Christians are promoting it. (This next discussion will be much shorter than this post, I promise).