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CletusDSpuckler t1_j9gnf5t wrote

Reply to comment by PJHFortyTwo in What are more accepted hypotheses that similarly explain the aspects of hominid evolution that the "pseudoscientific" aquatic ape theory does? by KEVLAR60442

>Sometimes our bodies evolve weird quirks, and there's no actual benefit, but also no cost to our actual fitness. E.g hair graying in our elder years.)

This cannot be restated frequently enough here.

As long as a trait doesn't negatively impact an organism's reproductive fitness, it might just be carried around for no good reason whatsoever. That's how evolution works - some changes are good, some are bad, and (probably) the vast majority are neither, requiring no further explanation other than mutations cause fun things to happen.

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Marsdreamer t1_j9hniym wrote

Evolution is honestly a lot more nuanced than people generally realize. Even deleterious mutations and traits can rise to fixation in a population despite our understanding of fitness models.

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Somnif t1_j9i4ccm wrote

Also important to note that Evolution doesn't work towards the Best solution.

Just the... least worst.

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Marsdreamer t1_j9i7yo9 wrote

Pretty true. To kinda expound on that, it works "up," but it can get stuck on local maxima rather than global maxima. Picture two mountains separated by a valley and one being higher than the other. If a species is 'climbing' the smaller peak of fitness then once it gets there it can theoretically never climb down the valley and start climbing the taller mountain. It will always* be stuck on that smaller peak because Evolution doesn't know how to take short term pain for long term gain. It's effectively a greedy algorithm to borrow from a CS concept.

*As long as conditions stay exactly the same. The adaptive landscape is always changing.

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dmilin t1_j9iuy2i wrote

This is believed to be the reason no species ever developed wheels despite them being incredibly efficient. It's simply too large an evolutionary jump.

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chx_ t1_j9j0pkh wrote

Also, sorry for the amateurish questions, wouldn't that require a rotating axle which is kinda impossible to develop? Like, everything is connected to the rest of the body. Maybe some weird symbiosis could do it? :)

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RestlessARBIT3R t1_j9i7s2v wrote

Exactly. You don’t have to be the best at something, just better than anyone else around you

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viliml t1_j9itljd wrote

The least worst is the same thing as the best.

What you probably meant was "good enough".

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KJ6BWB t1_j9iip77 wrote

> Even deleterious mutations and traits can rise to fixation in a population

To be fair, it requires a lot for a new mutation to spread through a population. For instance polydactylism, or having more than 5 fingers on a hand, is a dominant trait but despite its advantages most of still only have 5 fingers on a hand because it's really hard for a new trait to spread unless it confers a real evolutionary advantage, meaning those who lack it die and most of the survivors have that trait.

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asdqwe123qwe123 t1_j9juz61 wrote

Dominance also has no effect on how common a trait is, with fitness levels being the same, an allele being dominant doesn't make it more present within a population.

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TheDevilsAdvokaat t1_j9j3lgp wrote

Sometimes things we think are weird quirks actually have benefits we just haven't realised.

There's a severe cost for females having babies with older males. It's well known that over a certain age, babies from older men have increased problems.

As the father grows older, the number of mutations in the father's genome increases, leading to an increase in the incidence of congenital malformations in offspring [11, 65]. Older paternal age may be harmful to the offspring's health in terms of genetic mutations, telomere length, and epigenetics

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803514/#:~:text=As%20the%20father%20grows%20older,%2C%20and%20epigenetics%20%5B66%5D.

But how do you easily tell or estimate a male's age? Well, what about a signal like graying? Imagine if there was a signal that was almost universal among males, easy to spot at a glance, and a decent general guide to age?

I suspect graying is NOT a "weird quirk". It's just one we didn't realise the benefit of. There could be other good reasons for graying too. Graying may be an "honest signal" like stotting.

https://en.wikipedia.org/wiki/Signalling_theory#Honest_signals

I suspect there are a lot less "weird quirks" than people think; just misunderstood adaptations.

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F0sh t1_j9jegz2 wrote

It's advantageous to be able to identify less fit mates, but it's advantageous to look like a fit mate whether you are or not. It's difficult to have honest signals which aren't difficult to fake; you can't stot unless you're fit, you can't make an alarm call only when there are predators around unless you can detect the predator. If grey hair is energetically no more or less favourable than coloured hair then it would be difficult for it to spread as an honest signal of unfitness because it could just as easily be faked.

It seems more likely that grey hair is a signal for something else - age and hence some kind of experience/authority, or a side-effect of something else. Testosterone has a lot of effects, it probably has some that weren't specifically selected for.

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TheDevilsAdvokaat t1_j9jgso6 wrote

>If grey hair is energetically no more or less favourable than coloured hair then it would be difficult for it to spread as an honest signal of unfitness because it could just as easily be faked.

You're right. It's not an honest signal, because it can be faked.

However, while it's advantageous for individuals to fake, it's disadvantageous for the populations that contain individuals that fake.....so there's pressure to fake and pressure not to fake. Overall I would guess the pressure not to fake would outweigh the individual pressure to fake but it is just a guess...

>It seems more likely that grey hair is a signal for something else - age and hence some kind of experience/authority, or a side-effect of something else."

I agree. I showed a possible reason for gray hair, I am sure there are others. ANd in reality the total advantages for grey hair are going to be a SUM of the advantages and disadvantages. Whether that sum is a total positive or negative, who knows; the sign (+ or -) will probably differ depending on whether we're talking individual advantages or population advantages.

Which leads back to my original point; that some of the adaptations dismissed as "quirks" probably aren't.

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