/sci/ - Science & Math

>>15463531
It's the natural consequence of how the sex is determined. It isn't universal, haplodiploid species are predominantly female.

>>15463531
It's not 50:50. there is a slight male majority overall. you may say it is close to 50:50. as for how it does that, I don't know. but if it were any other ratio, the question would still need to be asked

>>15463575
Is that due to sex preference for male offspring, or naturally occurring?

>>15463582
naturally occurring. even after accounting for female babies that were killed off artificially, male births were still calculated to be higher.

>>15463585
I feel like I've read something about age and testicular temperature having to do with things, but I would have to look again

>>15463531
Gametes (haploid) from mom and dad that have a single copy of their chromosomes come together from each parent to make a zygote (diploid) that has a copy of both mom and dad's chromosomes (a 50:50 chromosomal ratio). It's simple mendelian genetics if you look at it on a punnet square.

>>15463582
>>15463585
Wouldn't a sperm cell with a Y chromosome have marginally less mass than one with an X chromosome, and wouldn't this explain the slight skew in favor of males?

>>15463531
Men have XY chromosomes
Women have XX chromosomes

Your sperm cells either carry an X or a Y
Obviously the mother has only X chromosomes and thus the sex of the baby is determined by the chromosome in the sperm cell
Since a sperm can either have an X or Y, the chances are 50/50

Now some retarded alt-right loser is going to chime in and make some stupid comment about intersex people or trannies

Yes sometimes people have abnormal chromosomes, some people have too many (such as the people who like to make such comments) and that can cause developmental disorders. Both men and women have the information for both sexes, the X/Y chromosome just activates those traits. XY females and XX males are not uncommon, something like 1 in 10,000, but sufferers rarely actually find out about this. Thanks to the horrors of science, we can also transplant your DNA and basically let any two people have children, since pretty much everyone except some very badly damaged freaks have at least an X chromosome.

>>15463747
There is actually a very slight skew right now in the world in favor of females. The skew in some countries towards males is cultural - people abort female children more often than male.

>>15463531
Uhm sweety sex isn't real. There's only the infinite multiverse of genders

>>15463531
>50/50 sex distribution at birth?
it doesn't

human natural sex distribution is 105men/100women. (21men/20women)

>>15463531
Nature flips a coin to determine the sex of the baby. That's how it works on the level of an individual. Evolution determines how the coin is weighted. If too many girls are born, boys are more likely to pass on their genes, so there's evolutionary pressure to weight the coin to produce more boys. That's how it works on the level of species.
>I'm sure there are some species that don't have this phenomenon
If there are, it's not a stable situation, since there is that pressure it towards 50/50.

>>15463760
>There is actually a very slight skew right now in the world in favor of females. The skew in some countries towards males is cultural - people abort female children more often than male.
The slight female skew is for adults. Males are far more likely to die before the age of 21 so the disparity essentially reverses between birth and adulthood.

>>15463760
>Men have XY chromosomes
>Women have XX chromosomes

Hey cool it with the hate speech, chud

>>15463588
Pressure also must be a thing. Seamen who operate in submarines tend to only have girls. There is a captain in the Spanish navy that tried for a boy and had to stop when he had 12 girls.

>>15463531
The mechanism is because sperm either have a Y or X and which one it is will basically be random which leads to a 50/50 split.
The evolutionary mechanic is that 50/50 split is favored for pair bonding species. If you imagine a world where say 70 were males and 30 were females then most males could not reproduce and mutations that increase the chance of a female being born would propagate until the ratio was back at 50/50