字幕列表 影片播放 列印英文字幕 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.....
B1 中級 為什麼男性往往更具身體攻擊性? (Why are males often more physically aggressive?) 173 4 簡宇謙 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字