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PJHFortyTwo t1_j9gmjao wrote

One possibility is that bipedalism evolved because it allowed us to free up our hands, allowing us to carry resources. Another is the endurance running hypothesis: that we evolved to become good long distance runners, and this shaped our legs.

I wouldn't assume that just because a trait evolved, like our hands wrinkling in the water, that it must have been evolutionarily adaptive. 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.

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CletusDSpuckler t1_j9gnf5t wrote

>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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alien_clown_ninja t1_j9hc2xj wrote

The endurance hunting hypothesis is on the same pseudo-science grounds as the aquatic ape hypothesis. Humans evolved in rocky terrain, where it would have been very difficult to track animals. And there is concrete evidence against it too. In the one place where animal remains with evidence of being eaten have been discovered alongside early humans, the bones were mostly adult and fit animals in their prime, not young or old which would be the easiest to catch by endurance hunting.

More likely is that early humans were ambush hunters, waiting in the foliage for an unlucky animal to walk by. It's possible that there were groups of humans that used endurance hunting, possibly for sport rather than survival (this is what the only groups of people who practice it today do).

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Ausoge t1_j9hgy53 wrote

However we do have several adaptations that are very well-suited to the endurance hunter lifestyle - the ability to sweat (quite rare in animals in general), hairlessness (which allows passive heat radiation as well as more effective sweat evaporation), a large surface-area-to-volume ratio (again, good for surface cooling), an upright stance allowing us to see greater distances than most prey animals, and bipedal locomation, which is not very fast but is extremely energy-efficient. We also have spectacularly well-adjusted physiology for the throwing of projectiles, which somewhat compensates for our lack of speed. Our combined torso and shoulder mobility is unparalleled in the animal kingdom.

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ToastyTheDragon t1_j9hj129 wrote

The high surface area to volume ratio surprises me. Do we have any data on, say, averages across different species to compare to?

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cookerg t1_j9ie7o8 wrote

So how did we get that endurance and running gait? However it evolved, humans are capable of covering longer distances in a day than most mammals, and do it voluntarily. And sled dogs might only be capable of keeping up, or beating us, because we selected them for it

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Kevin_Uxbridge t1_j9iuy46 wrote

Probably lots of moving about the landscape. Land tenure is something we know precious little about for our ancestors but it's reasonable to assume that covering ground can be advantageous generally.

Also, the image of early hominids running pell-mell after game presupposes some things about the world they lived in. Running down prey would, for instance, likely catch the attention of the local predator guild, who might be just as likely to steal your now-weary prey and kill you too. On the face of it, human cursorial hunting sounds ludicrously dangerous in most circumstances. The endurance hunting guys have no real answer to this.

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F0sh t1_j9jev6b wrote

> Also, the image of early hominids running pell-mell after game

Is not the image of endurance hunting. It's running at a steady, sustainable pace - a jog, really - that is not sustainable for the prey animal, which eventually cannot run more.

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[deleted] t1_j9iz4vs wrote

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drolldignitary t1_j9ja6l0 wrote

Alpha male?

If you are lying in wait where you know an animal is being driven, why would you decide to chase it to exhaustion in a days-long relay race around its herd, when you could jump out and kill it? So instead of one person wasting days running after a deer, it's...a dozen people wasting days running after one deer?

A days long, pointless, relay race in a big circle around its herd??

And what, the herd does nothing but sit around, and the animal never gets back to them the whole time?

Alpha male???

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beyelzu t1_j9jgqji wrote

> And sled dogs might only be capable of keeping up, or beating us, because we selected them for it

And they do it in the freezing cold, most of our endurance advantage is from not overheating after all.

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urbanek2525 t1_j9if8nu wrote

Also, there are many ways that things in our biology are interconnected and entantangled for no discernable reason. There are a lot of adaptations that have some good and some bad impacts. As long as the good outweighs the bad, it tends to stay.

For example, there is a drug that suppresses a man's body's ability to produce a particular protein. While that protein is suppressed, the man produces very little sperm. A near perfect male contaceptive. The thing is, in addition to enabling sperm production that protein also contributes to alcohol metabolism. So, alcohol makes the user very ill. There's no rhyme or reason that these two operations would be using the same darn protein, but they are. There are thousands of these overlaps that have developed over the millenia.

This is because there's no plan behind evolution. It's too complex to draw straight lines. It's a random mess.

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Treadwheel t1_j9ik046 wrote

That's not quite what's going on there. The drug in question worked by inhibiting aldehyde dehydrogenase, which is an enzyme which handles the direct metabolites of alcohol, but which isn't specific to just ethanol metabolism. All sorts of aldehydes are produced and consumed by the human body and need to be dealt with.

ALDH is involved in the conversion of retinol to retinoic acid, which is necessary to produce sperm, but the relationship is more of a general purpose tool having many applications than a bizarre coincidence of evolution.

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blujaibeauvais t1_j9hntol wrote

The idea that humans evolved because of our bums seems reasonable. Our butts allowed us to become good at distance, running that we would out - endurance animals sprinting away during hunting until the prey eventually gave up. Having more calories and then fire to unleash those calories or hypothesized in some circles to be a major change in our development

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Lindoriel t1_j9iyfdc wrote

Or could it not be that the hands wrinkling was a far earlier adaptation in our evolution which we just subsequently didn't lose?

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[deleted] t1_j9hov22 wrote

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[deleted] t1_j9i2oho wrote

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[deleted] t1_j9i5l3t wrote

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