It’s Evolution, Baby

Question from Nichole:
So, I just have a couple questions for those atheists who believe in evolution or those who would call themselves Evolutionists. I’m really curious what you guys think about it. So here are my questions:

1. In your thinking, what is evolution? How would you define it?

2. What do you think is the strongest evidence for evolution?

3. What empirical evidence are you aware of supports evolution?

4. Is there anything about evolutionary theory that makes you wonder about its validity? If so, what?

5. Are you aware of scientific evidence (or mathematical probabilities) that suggests evolution may not be true? If so what?

Answer by SmartLX:
There’s already quite a lot about this on the site so do a search in the top right for ‘evolution’ and other obvious keywords, but there’s no harm retreading old ground. I gather from your language that you’re neither an atheist nor an “Evolutionist”, so everyone has to start somewhere. I’ve numbered your questions for easy reference.

1. Evolution simply means “gradual development”. The demands placed upon followers of the God of Abraham evolved between the Old and the New Testament, for example, when Jesus became a requisite object of worship. Of course what we’re really talking about here is the scientific theory of Darwinian evolution by natural selection, which says that the first primitive life on Earth multiplied and diversified into literally all of the modern forms of life, including plants, animals and humans.

The theory of evolution takes no position on where that initial life came from; that’s a whole other area of investigation. It passes no judgement on the morality of the phenomenon, if indeed morality can even be applied to it, though some scientists have their own opinions. (Even Darwin wrote that “nature is red in tooth and claw”.) It makes no pronouncements on how we ought to behave, as it is merely an explanation and not a set of rules or guidelines. All it does is describe the development of life in all its diversity and complexity, accurately as far as we can tell from the evidence.

2.
I think the strongest evidence for evolution is the genetic and morphological (i.e. shape-related) similarities between living things. Almost every vertebrate animal has practically the same skeleton, but seemingly stretched, squashed and bent by countless generations of developmental pressure. Most of the same organs are there too. Two species of bird on one island may be able to interbreed, while seemingly similar birds from the next island over are incompatible with either species because they’ve been separated for too long. We share over 95% of our DNA not just with apes, but with any given species of mammal. Embryos of different animals look almost identical up to a certain point in their gestation.

In case you think all of this is simply signs that all life had a common designer, it doesn’t speak well of that designer because the similarities are not always a good thing. The appendix is useful to many animals, but about all it can do for us is kill us. Many deadly viruses and bacteria are just as at home in a human body as any other warm-blooded animal, which is why we can catch fatal infections from pigs or birds. The laryngeal nerve connects the brain to the larynx but it takes a detour all the way down by the heart in mammals, because the equivalent route in fish was more direct. (In a giraffe, it’s just ridiculous. Here’s a video where they’re dissecting one – it’s not too gory.)

3.
Everything mentioned above is empirical; you can see the evidence in your own body, anything else that’s alive, the recently dead and even the fossilised remains of ancient lifeforms. Really, the study of evolution is the direct study of living things, so there’s very little evidence for it which could not be called empirical.

4.
There isn’t anything which seriously throws the validity of evolutionary theory into question, or the controversy would be an argument between evolutionary biologists rather than between evolutionary biologists and religious creationists. Religion is the only reason anyone challenges it, which is why there are no secular opponents of the teaching of evolution (except for one fellow I know of, who makes quite a lot of money as a professional advocate). Not every religious person denies evolution as many prefer to see it as a divine method, but opposition to it has just that one source.

5.
Carrying on from #4, creationist evangelists present a wide range of claims about the natural world as arguments against evolution. They all have the same form: “Feature X could not possibly have come about naturally and gradually, or the odds are so small as to be practically impossible, so evolution can’t have produced X.” Even if no evolutionary path to the final result is known, this in all its forms is an argument from ignorance because not knowing how something is done does not necessarily mean it’s impossible. In practice, however, a plausible evolutionary method of producing the feature is often already known before the claim is made – the creationist just hasn’t looked it up.

I think that’s a fair representation of what atheists think of evolution, though any atheists reading this are free to correct me. So, tit for tat: what do you think of it, Nichole?