Comment by yesco | Hacker News Reader

Comment by yesco | Hacker News Reader

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I'm broadly speculating here, but I tend to view most mechanisms like this as evolution's "desire" for a well tuned, but imperfect, CRC check.

Ignoring whether or not it would even be possible, a perfect CRC is antithetical to evolution itself, wiggle room for mutation must always be possible, but too much mutation gives you cancer and systemic malfunction. So you end up with these bizarre processes that allow just the right amount of imperfection.

With sperm specifically it ends up closer to a signature check than just a CRC, if the sperm doesn't exhibit behavior that falls under a certain umbrella of expected behaviors, it's rejected by the surrounding environment. The difficulty to comprehend it could even be a feature of the process in many respects, especially when you consider everything in this realm risks getting "hacked" if precautions are not put into place.

So when I see huge numbers like this, I see it as an indirect measure of the precision of the overall process. To put it another way, it's like brute forcing a password you don't know, but happen to have a lot of hints to (since obviously, we are all still the same species at the end of the day).

I’ve actually had this question myself, “is there evolutionary pressure for imperfect genetic copying and repair mechanisms, since perfect ones would halt evolution and leave a species unable to adapt?”

I’ve asked this question to multiple evolutionary biologists, and all of them answered “no” very strongly, strongly enough that I’m inclined to believe it. Apparently the frequency of deleterious mutations is many orders of magnitude greater than the frequency of beneficial ones, meaning there’s little chance perfect copying could be maladaptive. And in any event, evolution always selects for the fitness of the individual, not the species— group selection is a controversial topic in evobio, but the general consensus is that it does not happen, and that the rare things which kinda look like group selection (e.g. eusociality in bees) actually aren’t and can be explained without it.

> And in any event, evolution always selects for the fitness of the individual, not the species— group selection is a very controversial topic in evobio, but the general consensus is that it does not happen

To me that seems more to me like a group of academics who just can’t see “how” it’d work. We’ve seen that in field after field where practitioners rarely look outside their own field.

There’s no “magic” in evolution to make it work only on individuals. Evolution is going to follow game theory. In some scenarios the evolution of the group will over time be far more adaptive than that of an individual. It’s a math question, not a biology question.

I suspect there could be a misalignment in semantics here, and not necessarily a disagreement. When a biologist says "evolutionary pressure" perhaps they have a different way of modeling what that means to them?

To me evolutionary pressure isn't an on/off thing, it's like a signal in the noise. It's a vector with a direction and magnitude, facing varying levels of environmental resistance.

To be more specific, if there was enough "magnitude", evolution could potentially arrive at a perfect CRC. But the "resistance" requires a "magnitude" higher than evolution is willing to pay to reach that perfection. Likely in part due to the implicit complexity slope. Considering the systemic malfunction mutation can cause, one might assume this magnitude would be higher than it currently is. However, this is entirely speculation, and not falsifiable.

So when I think of evolutionary pressure I'm considering it as a component of the final vector, where a biologist might more pragmatically consider the total sum of vectors instead. This way of thinking is likely more productive for what they are doing.

As for evolution always selecting for the individual over the group, I'm surprised this is controversial when it's so obviously happening? If that was true how could multicellular organisms even exist? I'm very much not an expert on any of this, but this sounds like perhaps an over focus on DNA itself and not evolution as a whole, but maybe I'm misunderstanding something?

> This way of thinking is likely more productive for what they are doing.

Which is… attempting a rigorous understanding of evolutionary biology, rather than idly ruminating.

I hate to use a dork-ism like “update your priors”, but this is actually maybe a situation where it applies? If you’re serious about a subject it’s more interesting to really incorporate the likelihood that you’re wrong than it is to wave it away as semantics or point of view.

I find evolution interesting because I like algorithms, so I view it through that lens. There is absolutely nothing wrong with this perspective. Clarifying my mental model is by no means simple hand waving.

Tell me this, which is more productive in an open discussion? My idle rumination? Or the lazy dismissal that lacks any substantive contribution to the ongoing discussion? I can't help but agree with your distaste for "dorkisms".

This is one of those issues where I think that the experts in the field saying that are just plain wrong. I know how that is a bad assumption to start out with; but I also know that obviously there is an amount of mutations that is beneficial, and organisms with a rate lower than that will be outcompeted. It could be no other way.

So is it just misunderstanding? Maybe they don't understand the question, or we don't understand the answer? Or they're hidebound, or incentivized somehow to be blind to the truth? Epistemological questions abound.

Imperfect copying is only one reason for having to reject many sperm cells, and a less important one.

Meiosis, which produces both the sperm cells and the egg cells, is not a copying mechanism, unlike mitosis, which generates the other cells of a body.

Meiosis is a random generator, it randomly shuffles the DNA of the grandparents, which is stored in the father's cells, then it randomly selects half of it, producing a unique combination of genes in each sperm cell or egg cell.

The random genome generator together with the following filtering steps that will reject the bad variants, implement an optimum search algorithm for the fittest descendants.

Meiosis has greatly accelerated the evolution of the nucleated living beings (eukaryotes). Because favorable mutations are extremely rare, the probability of a living being accumulating multiple favorable mutations would have been negligible. With meiosis, if in a population 5 individuals have 1 favorable mutation each, there are good chances that soon some individuals will appear who have all 5 favorable mutations, then their descendants may become dominant and replace all others.

But there are also Microsatellites https://en.wikipedia.org/wiki/Microsatellite#Mutation_mechan... that are repeated sequences in the DNA. It's difficult to copy the correct number of repetitions, so they have a higher mutation rate. It's like like a controlled localized increased rate of mutation.

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