Name: Why are males often more physically aggressive?
Uploaded: 2016-09-10T16:33:56.000Z
Duration: 6 min 49 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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,