The Evidence for Evolution Part 1

When I was growing up, I never for a minute considered that evolution might be true. I already “knew” that the Bible was the inerrant word of God, so evolution was simply error. And in my high school biology classes, our teacher made it clear that she had to teach us about evolution by law, despite the fact that she didn’t believe in it herself. I had a handful of friends who believed it, but we never really talked about it. Even if they had, I knew they weren’t “true” Christians, so it was no surprise that they held “inaccurate” ideas.

Many years later, after I had left Christianity, I decided to give evolution another look. I was completely blown away by the amount of evidence I encountered. And so many of the criticisms I had heard against it, that it was “only” a theory, that the fossil record contradicted it, that it had never been observed, that positive mutations were so rare there hadn’t been enough time for this diversity of life to develop, etc were all untrue.

Now as I stated in my last post, I don’t think evolution and religion have to be at odds, so I’m not trying to criticize religion in this post. I think there are many ways for Christians to hold onto their faith while also accepting what science tells us about evolution. So without further ado, here’s the first post in a series that will present some of the evidence for evolution:

Geographic Distribution — Microevolution
When Charles Darwin was a young man, he spent 5 years traveling the world via the HMS Beagle. During the voyage, he managed to spend some time in the Galapagos Islands, about 600 miles off the western coast of South America. One of the things that really struck him was the diversity among the various species of finches there. He identified at least 14 different species, each of which had beaks that were specially suited to their particular food source: ” three species of ground-dwelling seed-eaters; three others living on cactuses and eating seeds; one living in trees and eating seeds; and 7 species of tree-dwelling insect-eaters” [1].

This type of variation is known as adaptive radiation, and it’s a form of microevolution. In case you’re not aware, microevolution is a term for the changes that occur over time within a species — different breeds of dog, variations in height among a population, etc. Almost no one objects to this type of evolution. Macroevolution is a term for the changes that occur over time from one species to another. Quite a number of people object to this version of evolution; however, it’s really no different than microevolution. It just requires a longer period of time.

How did Darwin’s finches evolve once they reached the Galapagos Islands? As they settled among the different islands, they encountered different food sources. Scientists believe the first finches that arrived there were of the ground-dwelling, seed-eating variety. Some of the birds wound up in places where their typical diet was more scarce, but larger, harder seeds were available. As you might imagine, the birds with thicker, stronger beaks could eat that food more easily than the birds with thinner, weaker beaks. They survived better, and simply out-bred the others. Since they were separated from the rest of the finch population, the changes in their physiology became more and more pronounced over time. So there are two factors that are very important in evolution: separated populations and scarce resources.

But the importance of geographic distribution goes much further than this example. Islands are isolated from the other main land areas. Not-so-coincidentally, they also have vastly different plants and animals. Hawaii, for instance, had no land animals until the arrival of humans. There were only birds, bats, and insects living there. Considering how far away Hawaii is from other land masses, it makes sense that if any animals were to migrate there, they would be flying animals. However, if God had created all animals exactly as they are today all at one time, there’s no obvious reason why he would have left Hawaii barren. If it had been teeming with the typical creatures we find elsewhere, that would have been good evidence against evolution.

Australia is also isolated from the other continents, and it provides another fascinating example. Prior to humans, Australia had no placental mammals (dogs, cats, deer, horses, etc). Instead, it contained many species of marsupials that never developed anywhere else in the world. While koalas and kangaroos are some of the most familiar to us, there are other marsupials that developed in Australia to fill niches left empty by the animals most of us are more familiar with. For instance, Australia had no wolves, but Tasmanian tigers developed to fill a similar role. Australia had no cats, but the Thylacine developed to fill that niche. Instead of rats, Australia has bandicoots and bilbies. If God had created all animals just as they are all at one time, why create marsupial versions of animals when there are perfectly good placental animals that could have filled the same roles? And why do it in such an isolated spot? But when you look at it from the view of evolution, it makes much more sense. Marsupials found their way to Australia long, long ago, when Australia, Antarctica, Africa, and South America were all part of a larger continent, Gondwana. When that continent broke up, and Australia began to drift away, the isolation necessary for evolution was achieved. As time went by, more and more changes occurred among marsupials, culminating in the various species we know of today.

But that may be jumping the gun a little. It’s one thing to talk about differences among finches, but one species changing into another is a completely different matter. How could that be possible? We’ll get into that; just follow along.

Part 2 can be found here.