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  • Ok, let's ignore everything we know about males and females for now. So like males aren't

  • mustached beer drinking slabs of testosterone and it's possible to leave a girl alone with

  • your chocolate. Let's break it down to the basic definition

  • of male and female. What we call a male will be the genetic class

  • or genetic variety of a species that produces the smaller sex cell, the smaller gamete.

  • The female makes the larger ones. The females gametes move around less, they take more effort

  • to make and the females are almost always the ones that store the babies as it gestates.

  • So let's make two different communities. One is made up of 9 females and 1 male and the

  • other 9 males and 1 female. In terms of reproduction what might we see differ?

  • Well, in the first, the male could fertilize all 9 females... probably in the same day.

  • And then after, let's say 5 months for whatever this thing is, all the females would have

  • an offspring, and the male would have lots of offspring.

  • OK. What about the other community? After 5 months, only the female and 1 male will

  • have a baby. And then what, it's someone elses turn?

  • Creatures want to leave behind as many offspring as possible. And they could get killed by

  • falling rocks tomorrow, they really want to reproduce as soon as possible. They're all

  • going to want to breed and they're not going to want to share. So they'll fight over her.

  • This is a part of why all over the animal kingdom, you see the males being more physically

  • aggressive than the females. Because females are more of a scarce resource to male reproduction

  • than males to females. From the female's point of view, she can pick

  • whatever male she wants as a mate. She also wants to make as many offspring as

  • possible but because she can only produce 1 every 5 months, she'll be choosier with

  • whom she mates with than a male is. She'll want to pick a mate that can make children

  • that have a high chance of reproducing. Maybe the biggest or strongest? Since the biggest

  • and strongest win the mating rights among the males? And is maybe a sign that this guy

  • survives well and his kids will too. I'm not using the word "want", to say that

  • they necessarily literally want something. Like they're sitting there working what the

  • best strategy is for spreading their genes around.

  • Rather I'm personifying the genes or the individual as having wants as a short way of saying that

  • "everything else being equal, females that are genetically inclined to being attracted

  • to big strong males, will leave more behind offspring or offspring with a higher chance

  • of reproducing compared to females who are not attracted to big strong males ".

  • It's want in the sense that if that individual has a gene that codes for that thing, it will

  • reproduce more. So it can kinda seem like that's what genes

  • want to do. But there's a problem with this, saying that

  • genes directly control behaviour. Which isn't true right? There's no gene for say: driving

  • a car. Gene's do influence your arms, your legs and your brains that facilitate and create

  • the motivation for the behaviour. But saying that a gene controls a behaviour. It's a bit

  • incomplete. When dog breeder picks what dog gets to breed

  • based on what behaviours make a good pet, what they're really selecting for are the

  • genes that create a certain brain structure. But also a dog trainer.. can change that brain

  • structure and behaviour by training and controlling it's environment.

  • Is there even a genetic component to her mating with this big strong guy? Maybe it's entirely

  • environmental. Maybe he's just intimidated or even physically dominated her into mating.

  • Your genes and the things that happen to you are what shape your phenotype. You could have

  • some mutation that makes it so that you only have 1 arm. But you could also lose an arm

  • in an accident or something. Seeing a behaviour and assuming a gene directly influenced it,

  • is the same as seeing someone with one arm and assuming a gene directly influenced that.

  • It may be true, but we haven't demonstrated that.

  • I'll come back to this later maybe... for now let's ignore any environmental factor

  • and just look what the genes might do and assume: gene... boop... behaviour.

  • Let's look at 2 broad ways a community's social structure could evolve.

  • You could have just the one largest, strongest male intimidating everyone and mating the

  • females. Because he can fight and win to cock block any other males that tries to mate.

  • Animals with social structures like this could be described as a tournament species. Because

  • here you have one geneder, usually the males, competing for the favour of the other gender.

  • In a system like this you would probably get a minority of the males mating with all the

  • females. Since he's one if the few who gets to mate, and he's is probably one of the largest

  • and most aggressive, future generations will continue to have males that are larger and

  • more aggressive. That power may change hands often but still favouring the strongest....

  • or just the male with the most impressive display of health and strength and good genes.

  • So with a tournament species, you would expect to see a lot of sexual dimorphisms, a lot

  • of differences in the size shape and behaviour between the sexes.

  • You can even use sexual dimorphisms to predict the behaviour of the species. This is the

  • sort of thing you see in chickens, savannah baboons, lions, moose, gorillas, all have

  • males larger than the females and they all exhibit some sort of tournament system.

  • Because whoever is on top is too concerned with maintaining his alpha status, and they've

  • got too many kids to care about, the females do most of the raising of the kids alone and

  • tend to have evolved to only produce 1 child at a time. Otherwise they might have their

  • hands full and be able to give proper care to each of their children.

  • But you could have a completely different social structure. One where where both parents

  • are taking care of the kids. With more parental care the kids would have a better chance at

  • reproduction. And since the females have some help, the females would be able to produce

  • more than 1 child at a time benefiting their reproduction.

  • Since the males are busy taking care of kids alongside the females, you tend to get a larger

  • majority of the males mating, rather than spending their time jockying for alpha.

  • Since they're not fighting, and the females are selecting for parental care, he wouldn't

  • have evolved big useless muscle or dramatic features like colourful feathers and you would

  • expect to see less sexual dimorphism. This could be called a pair bonding species.

  • A good example of this is the marmoset monkey. You can't really distinguish the males from

  • the females by looking at their behaviour or their body unless you looked real close.

  • But pair bonding or tournament species, these are just more categories that category people

  • make. They're useful as very broad ideas for describing some patterns between social structure

  • and physiology. But they're not entirely predictive. In baboons, where the males are super aggressive

  • and can be twice as large as the females, there might be a subordinate male who's too

  • old or too weak to ever have a chance at being alpha. But he could approach a female and

  • groom her a lot and otherwise woo her with his parental skills and they may have sex

  • in secrete in a more pair bonding fashion. And you can have a situation where the entire

  • community that doesn't follow the "mating rights through violence" regime.

  • In spotted hyenas, it's the females that are larger dominant. Even the lowest ranking female

  • in their dominance hierarchy is dominant to the highest ranking male.

  • And I'm pretty sure every bonobo is just bisexual. Which increases their chances of getting a

  • date, but demonstrates there's more going. And what about humans? Human males are larger

  • and more physically aggressive than females and females produce single children. But most

  • cultures have some sort of monogamous marriage system. But again, a lot of marriages end

  • and we don't seem to mate for life. And females can be attracted to both dominant traits and

  • parental traits. Does she go with the muscular competitive guy who is genetically predisposed

  • to taking his shirt off, or the older more mature guy who has feelings and stuff....

  • or maybe both at the same time. Like a lot of species we would be somewhere

  • in between these 2 classifications. In reality it's not about tournament or pair bonding,

  • it's just whatever works.

  • So the decision becomes pretty straight forward: you gotta kill the kids... you just... you gotta kill em. You need that baby mama to be your baby

  • mama but she can't if she's already pregnant or maybe she's just lactating and won't ovulate

  • till she's done. If you're the mother you're going to want to protect your kids, but you're

  • not going to put of so much of a fight.....

Ok, let's ignore everything we know about males and females for now. So like males aren't

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なぜ男性の方が身体的に攻撃的なことが多いのでしょうか? (Why are males often more physically aggressive?)

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    簡宇謙 に公開 2021 年 01 月 14 日
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