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Comment by fiatjaf | Hacker News Reader

One common counterargument I ever head when talking to evolutionists is that some mutations are linked to others, so a mutation can spread through the population even though it does not confer any evolutionary advantage because it genetically linked to another evolution somewhere else that indeed confer advantage.

What do you think of it? Is it serious enough? Because I think there is an obvious flaw in it, the question: why are these mutations linked?

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I think you are talking about something known as hitchhiking mutations. Suppose an organism develops two mutations A and B, which lie close together in the chromosome. A is beneficial and B is neutral. When the chromosome is copied during reproduction, the copy will contain both A and B (because they are nearby). This copy will have an overall advantage because of the presence of A, and will spread in the population. https://en.wikipedia.org/wiki/Genetic_hitchhiking

Right. Thank you, that's probably this.

But the question remains: who put these genes near each other, so that something would evolve without being naturally selected just because its gene was near another gene?

What is the likeness of a gene near a gene that's "evolving" to be important somehow in the future of the evolution of that species?

No one did. That's not how evolution works. There is no plan, and no one decided how it would work in the future. Your second question makes me think that you're thinking of evolution as "progress", that everything is evolving towards something. It is not. That is, you're asking, given an adaption, what is the likelihood of those genes existing? But that's backwards; the genes caused the outcome.

You're trying to insert purpose or intent into what is essentially accident. Most -- almost all -- changes like these either never have lasting consequences or are eventually undone. They are insignificant, and may not even have expression, unless and until they become significant because of subsequent changes.

You can insert supernatural interference into the process -- there's nothing but the principle of parsimony (Occam's razor) preventing that -- but you can't require it in order for things to work the way they apparently do/did work.

I'm happy you're open to learning more about evolution.

Genetic linkage is a fairly advanced concept. For example, this (great) introductory Yale course doesn't even mention it. http://oyc.yale.edu/ecology-and-evolutionary-biology/eeb-122...

Every gene is next to another gene. You are right, the scenario you are detailing is unlikely - correspondingly, it happens very rarely.

Complex things we don't understand often seem magical.

There are many reasons. Life re-uses structures, hormones, and proteins in different areas of the body for different functions. A mutation can make a structure more efficient in one area and have little effect in another... for now, but many mutations later that mutation can become a key enabler of a whole new class of features from the secondary structure.

It may also be that the gene doesn't confer any specific advantage but a population bottleneck or isolation event can spread it nonetheless.

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