What Even is Evolution by Natural Selection, Anyway? A Beginner’s Guide


I saw a discussion online today started by someone who, like me, attended a private fundamentalist Christian school as a child. They have long since left the fold, so to speak, and accept evolution is true, but they confessed to not fully understanding it.

This was unsatisfactory to me. They only accepted it was true because it was rejected by their religion, and upon learning their religion was untrue, they assumed everything it opposed as a falsehood must in fact be true. That’s just more faulty reasoning.

Many who leave the faith struggle with reasoning because they were never taught how to do it, and often were specifically taught not to evaluate the credibility of claims using reason, but rather the degree to which said claims are consistent with the Bible.

However it made me realize there’s a real need for an entry level primer about evolution. Not written for children but for the adult layperson who was raised in an environment where they were both prevented from researching what evolution is, and fed misinformation about it in order to make them reject it.

This was the case for me. I was told all sorts of lies about evolutionary science while attending that school, such as “evolutionists believe all life descended from rocks”. Or that the piltdown man hoax proves all of evolutionary science is a hoax (or hackel’s embyro illustrations, though his inferences about ontogeny recapitulating phylogeny were essentially correct), or that human footprints have been found inside fossilized dinosaur footprints, or that if evolution were true, the monkeys at the zoo would be turning into humans before our eyes.

Maybe much of that seems ridiculous. But if you’re raised in an insular echo chamber where you only get one side of the story, and all the adults who seem authoritative, credible and smarter than you say evolution is impossible, you would likely assume that’s the case.

I’ve had many commenters on my blog leave long, elaborate arguments in the comments section of articles like this one because they think I just don’t understand their sophisticated, intellectual form of creationism. They think I haven’t heard their particular obscure apologetic argument. They think it is I who does not understand their position rather than the reverse.

However it’s been my experience that if you can explain evolution simply enough, using examples from everyone’s common day to day experience which they know to be true, then they cannot help but recognize it is true. They do not always fully accept it, wanting to compromise parts of it to preserve their religious beliefs. But they do accept to some extent, once you show them how obviously true it is, that species change over time.

Without further delay, a beginner’s guide to what evolution is and how it works, followed by some commentary on common confusion and disinformation related to it:


You know how babies have some of their father’s DNA, and some of their mother’s DNA? Because sexual reproduction combines DNA from both sources?

That’s called heritability. Offspring inherit genetic traits from their parents. Because this principle was understood long before anybody even knew what DNA was, they were able to use that understanding to do selective breeding.

Selective breeding is where a farmer decides he wants more cattle with a specific trait. So the ones who have that trait are permitted to breed, while others are not.

This results, very rapidly, in the replacement of all individuals in that group of cattle who didn’t have the trait, with ones that do.

Natural selection works the same way, but instead of a farmer choosing who gets to breed and who doesn’t, it’s circumstance. Mostly the environment and how good individuals are at surviving in it.

Traits that make an individual bad at surviving lessen their chances of reproducing. They just don’t live long enough to reach sexual maturity or find a mate and make babies.

Now, sometimes they do. Not every individual with that trait has to fail at surviving/reproducing for natural selection to occur, just more of them on average than the individuals of their species who don’t have that trait.

This means over time there will be fewer and fewer individuals with that trait. It causes changes way more slowly than selective breeding because there’s no farmer or other intelligence deliberately constraining who breeds, it’s just a statistical tendency of individuals with traits that aren’t a good fit for their environment to succeed at reproducing less frequently than the rest.

That’s what it means for a trait to be selected against. For a trait to be selected for, it’s much the same but flipped around: The trait turns out to give some small advantage.

It doesn’t have to be huge, just something which makes life a little bit easier. It doesn’t mean individuals who have it will survive to maturity and reproduce every time, just somewhat more often than those who don’t have it.

The result? Over many generations, individuals with this trait become more numerous, and a larger and larger percentage of the species on the whole.

This is how over time, “bad” traits which make survival and reproduction more difficult are weeded out by death, and “good” traits which make survival and reproduction easier become more prevalent until they are found in every member of the group.

Now, take what’s written here, and think about this same process happening not to a single trait, but simultaneously to every genetic trait that defines an organism. Natural selection does not act on one trait at a time, but all of them at once.

Also think about how these changes will accumulate over very long timescales. As the environment changes, more and more previously “good” traits become “bad” traits and are weeded out of the genome, because those traits were suited to environmental conditions that no longer exist.

At the same time, traits that would not have been good in the old conditions are suddenly very useful, and will be selected for, becoming more and more common in the gene pool.

Because the environment never stops changing (except in a few unusually stable niches, which accounts for why many deep sea species have remained mostly unchanged for eons) you can see how the genome of any species living in that environment will undergo constant change along with it, losing some traits while gaining others.


Eventually so much change will have occurred that the species will be unrecognizable compared to its distant ancestors. Creationists argue that this can’t happen; that some unspecified force will stop canines, for example, from changing so much that they are no longer recognizably canine.

This is their concept of “kind”. Most acknowledge that humans selectively bred wolves into modern domesticated dogs, but hold that this doesn’t prove evolution because dogs and wolves look very similar, and thus are the same basic “kind” of animal.

The problem is, “kind” is not rigorously defined. It’s just “what type of animal it looks like to a creationist”. Nor do they ever explain what exactly would stop a species from evolving beyond the point where it’s no longer recognizable compared to its distant ancestors.

Birds, for example, descended from dinosaurs. This is a big problem for creationists because of the well preserved fossils of archaeopteryx, with feathered wings, but the head of a small dinosaur. Also the dormant dinosaur genes still in modern birds.

Genes selected against are not truly erased, but switched off. “Dormant”. So that if conditions abruptly change, those traits don’t have to re-evolve. How? Those species whose DNA had this feature were able to adapt more rapidly to environmental change than those whose DNA did not store dormant ancestral traits.

Because of this, it’s possible with genetic engineering to turn dormant genes back on. In chickens for example, doing this results in dinosaurian features. Sharp teeth, featherless bodies, long tails, etc.

Re-activation of dormant genes in humans can result in babies being born with tails. All human embyros develop tails, but they are normally absorbed into the tailbone prior to birth. Many other ancestral features can be seen in embryos in the different stages of development, for reasons explained here.

I’ve written a great deal about this, but it seems to fall on deaf ears in situations where someone has firmly decided what they believe, especially when they hold those beliefs for emotional reasons. But even for such people there are questions related to this topic worth dwelling on.

Why do Christian educators, pastors, etc. devote such special attention to smearing evolution? They do not similarly dispute most other areas of science. They have no issue with any field that does not contradict Biblical claims. We are for some reason expected to believe that scientists are honest in those areas, but uniquely conspiratorial and deceptive in the fields of biology, geology and any other discipline which has produced findings contrary to a Biblical, young Earth creationist worldview.

Does that not seem at least slightly contrived? Does it not make more sense if viewed from a different angle, that they devote so much energy to hiding the actual definition of evolution from their children/students because it does in fact disprove the Biblical account of human origins, and they don’t want their children/students to conclude that Christianity is untrue?

What else explains such organized, deliberate misrepresentation of evolution in Christian schools? Shouldn’t it be enough to give an honest, accurate account of what biologists hold evolution to be, and how it works? If it’s so plainly wrong, why lie about it? Why teach intentionally false, absurd definitions of it?

Poorly photoshopped images of giant nephilim skeletons, the countless claims to have located the wreckage of Noah’s Ark, the admitted lies of the boy in “Heaven is for Real”, the Cassie Bernall hoax and more ought to demonstrate exhaustively that Christians have a long history of circulating faith-promoting lies.

Their reason for doing so ought to be self evident: In their mind it’s justifiable to promote a lie if it causes someone to convert to Christianity, because they believe it will save that person’s soul. Never have they considered that perhaps they were only led to believe conversion saves somebody’s soul, in order to make them feel compelled to recruit as many people as possible into Christianity.

I digress. The point is that there’s a long, well documented history of Christians knowingly lying in an effort to make Christianity appear more credible, and to discredit any scientific findings which contradict scripture. What reason is there, then, to suppose they aren’t doing the same thing when they misrepresent evolution to students?

Mark Twain once said that it’s much easier to fool a man than it is to convince him that he’s been fooled. I lament how true that is, because I’ve undertaken the tedious and thankless task of convincing millions of people that they’ve been fooled.

I’m not sure what else to do, as somebody who treasures truth. Not what a book says is true, or what feels true in my heart, or what I wish to be true, but what can be shown by experiment, forensic science and supported by good reasoning. I hope what I’ve written here will effectively serve that goal.

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