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Comment by Udik | Hacker News Reader

> During a single reproduction, there are tons of genetic and epigenetic variables that could be selected for, which determine different things. Why would a specific feature in a specific part of the body, that provides merely a minor improvement at any given time, come to completely replace all other genotype expressions?

As far as I understand it, sexual reproduction with its gene shuffling allows all features to evolve simultaneously. So the genes for the anorectal angle are constantly selected across the whole population in parallel with every other gene.

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Have you ever seen the mathematics on this? When so much is being selected "at the same time" it seems like most of the time it would never get selected in the wash. After all, selection works on an individual organism, and it's binary: either the organism survives, reproduces and passes on its genes, or not (we are not talking about DNA swapping between microorganisms here). This binary signal is supposed to be the "vote" for whether a particular combination of genes is more fit or not. But you can't just say "it's all possible given a really long time", you'd have to actually quantify what the chances are of say, the mechanism a single vote selecting simultaneously 1000 different traits, would increase the prevalence of all the "beneficial" traits. Do you have enough resolution to decide e.g. whether the bone density, color of skin or the length of legs was the factor that led to survival?

I am especially not sure why it would select the traits -- like a colorectal angle -- that would make an individual simply more comfortable rather than make a tangible difference to survival.

If we took the predictions of evolutionary theory seriously, then their contrapositive seriously too. In particular why would gay people exist if genetically homosexuality confers a much lower genetic fitness? Why do we say homosexuality is primarily genetic if evolution is true?

> Why do we say homosexuality is primarily genetic if evolution is true?

In my opinion it must be to help the fitness of the community they live in. The communities with low likelihood to spawn a gay person are (were?) much more likely to go extinct. It can also be a basic property (side effect?) of the sexual appeal arms race.

There is also the case of suicides, when they happen to young people that hasn't reproduced yet. It can also be argued its for the benefit of the community.

So the thesis is that the primary force in evolution is not individual's fitness but it is the community's fitness.

See that just further goes to show my point. Where is the evidence of these assertions? Mainstream evolutionists have said that "group selection has been disproven" except possibly kin selection. So your example clashes with what they've said.

https://en.wikipedia.org/wiki/Group_selection#Good_of_the_sp...

I personally think the benefit of the community is definitely one of the factors. And I think the evolutionists have it wrong. But why does the public just accept whatever they say? It hardly sounds like a settled theory.

What you linked says "On the other hand, kin selection is accepted as an explanation of altruistic behavior.[11]"

So, an extended family with a few homosexual kin might have greater reproductive success with their offspring having more caretakers.

Meh, it is not necessary to postulate that every part of behavior to which genetics contributes is a thing which has been selected for.

If a particular gene causes good things 95% of the time (based on other interactions or developmental factors or whatever) and catastrophic failures like heart disease or cancer or crippling depression 5% of the time (and it represents a local maxima, with no simple improvements possible), then it can easily come to dominate a gene-pool, so long as the 95%-benefit outweighs the 5%-failure. It doesn't mean the 5% failure has been "selected for", it just means that it wasn't worth weeding out.

Moths circle lights because of genetic factors which influence their tiny moth brain's development. It doesn't mean that circling-lights was a selected feature.

So what are the genetic advantages of being gay? And how come nature hasn't figured out a way to make these advantages without also producing gay siblings, which would seem to bring down the overall fitness of the genes?

Birth order has been correlated with the statistical likelihood of an individual being gay (i.e., the more older siblings you have, the more likely you are to be gay). This could definitely pose an evolutionary benefit to a stable population that lacks the natural resources to support a sudden boom of growth. Case in point being pandas which I just watched a show about last night that put forth pandas' low reproductive rate as ensuring low competition for their precious bamboo.

Since the first comment didn't work, I'll try going into more detail.

Our genetic code doesn't include statements like "if (is_male) { try_to_have_sex_with_ladies(); } else { try_to_have_sex_with_dudes(); }".

Our genetic code produces proteins of different shapes and those shapes influence the development of the structure of our brains and their function and that brain generates feels of various kinds that lead to attractions of various kinds.

Evolution works by changing the coding of the genetic code which changes the shapes or amounts of proteins produced which changes the development... a local maximum happens when the final system produced (our feels of attraction) would be negatively affected by any individual mutation on the genetic code. There may be better feels-of-attraction systems you could build from scratch that would propagate the species better than ours, but you can't turn ours into this better system without making it worse for awhile.

Nature can't make arbitrary changes; it can only make incremental changes. And consequently, we frequently get stuck at local maximums rather than global maximums.

Yeah, that's definitely a possibility. What you describe is more or less the basic property/side effect I was talking about, but much better explained.

You're betting evolution is not that good. One can also bet it better than you can possibly imagine. I don't think you can be sure either way at this point, but your argument seems to be the most compelling at this point!

Traits aren't evenly distributed throughout the population. Natural selection doesn't operate on the individual level, but at the _population_ level.

In other words, there is no "wash"-- genes aren't all shaken up until they're randomly distributed.

> After all, selection works on an individual organism, and it's binary: either the organism survives, reproduces and passes on its genes, or not

Not quite. Selection isn't a 'did reproduce' / 'did not reproduce' binary - there's lots of in-between.

1. At the macro level, any given trait doesn't exist in a single organism, it exists in multiple organisms. Even assuming that an organism reproduces only once, or not at all, among a large population, the individual binary gets washed into a larger, fuzzy, aggregate.

2. A "binary" seems to assume that an organism can reproduce only once - many organisms reproduce multiple times.

3. A "binary" seems to assume that once reproduction happens, the vote is cast and the trait has (at least in aggregate), "won". Merely reproducing isn't good enough, though - most complex organisms have to continue to rear their young after birth.

Yes, obviously the binary decisions are being aggregated, but at the end of the day, everything is filtered through these binary decisions. It's not like "I survived and reproduced and it was all because of X". It's just a binary outcome every time an animal reproduces. It's a vote for a certain combination of traits out of myriads, and now you have to show mathematically that this sort of selection can lead to evolution.

And also keep in mind, the "beneficial" mutation step happens in only one animal, that had the mutation when the genes combined to form its genetic expression. And you need several of these steps. It's not like all of a sudden a bunch of proto-birds started to develop wings. Just one animal developed a proto-wing trait, and then reproduced along with 99.99% of others who didn't. But then, the proto-wing happened to be so beneficial despite not conferring an ability to fly, that the proto birds with the proto wings simply died less than the other 99.99%, and started growing in prevalence. And all this still assumes that, at every step from non-wings to wings, the improvements were beneficial for genetic fitness. Now, what if they weren't? How can evolution wait until a string of mutations detrimental to fitness takes place? Wouldn't that make the population with the proto-wings actually shrink -- when it was already 1 animal or so, it might actually be eliminated if we assume proto-wings were genetically disadvantageous before becoming wings?

Again, there is no math in these explanations. Just descriptions and handwaving. Where is the actual math backing these claims and the explanation of the mathematical results! How does it actually work out? It clearly doesn't seem like it should!

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