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mikerbyrne73 t1_jdpxj5b wrote

I was taught it is because the Y chromosome sperm are slightly lighter, therefore swim faster and have a higher chance of fertilizing the egg.

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Thin-Rip-3686 t1_jdqup8u wrote

There’s only about a 3% difference in payload mass between the two.

Although it’s also been theorized that the lion’s share of the difference is because female embryos spontaneously die at a higher rate, there’s also the theory that eggs and sperm communicate with chemical messengers and eggs may prefer one sperm to another.

This set of preferences as well as the distribution of X vs. Y sperm also correlates to both parents’ stress and methylation levels- an easy life so far means creating males is better because if successful they’ll make more babies of their own, whereas a hard life so far means creating females is better because their success is a safer bet, even if they can’t make as many babies.

That logic may be backwards, or even reversed between sperm and egg.

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Tyrrox t1_jdqyov4 wrote

I’m no science dude, but I would think a difference of a 2% spread could easily be accounted for by a 3% shift. 51 is only 4% larger than 49, and 2% larger than 50.

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Thin-Rip-3686 t1_jdr6ejt wrote

You forget the importance of percentage of overall mass. It’s probably more like the race performance difference of two identical cars, one with 3% more fuel in the tank, versus one with 3% more overall weight.

Little effects like this can produce outsized results or no change in results, but the “sized” result is way less than 2%.

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kelldricked t1_jdt4sfu wrote

That second thing seems unlikely because it wouldnt explained the “returning soldier” effect. A weird “event” were more males (relative to woman) are born after things like wars.

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tullystenders t1_jdpvp9i wrote

I woulda thought opposite. Cause a species could use more females than males.

Another comment said, for fertilization, it's about equal.

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a_trane13 t1_jdqp32b wrote

Human females are 2-3x less likely to die between 18-45 so I wouldn’t just assume humans in particular could “use more females”.

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UnderstandingAshamed t1_jdpnqo1 wrote

I have read that female embryos die more often.

The ratio of male/female fertilization were roughly equal. .

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[deleted] t1_jdpocxf wrote

[deleted]

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justlurkingdnd t1_jdpxn7d wrote

Ah one of the things that makes me happy is knowing that we know a tiny portion of what’s really going on .

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fredsam25 t1_jdqn5cq wrote

There is no single cause. In aggregate, more males than females are born. Some of it is from the dna distribution in viable sperm, some of it is viability in the womb, some of it is generations of selecting for male babies (post birth abortions of females) making a those that naturally abort female fetuses because of genetic flaws more likely to pass on their genetics, and some of it is still not known.

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IkmoIkmo t1_jdqjy0s wrote

I wonder how long that's been the case, and if via evolutionary theory it gave rise to physical and indeed cultural gender norms, around strength and competition and such.

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After all, while it's a bit of a stretch, just to hypothesize: in a world with 8 billion people, having a 51/49 ratio means there's 3.90 billion women to 4.1 billion men.

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In other words, there's 200 million men who by definition will not be in a relationship, assuming 100% of possible people engage in an exclusive relationship. That's 200 million men constantly competing to become one of the group of 3.9 billion men. Depending on status, men are able to join the group, or fall out of it. But the default state is to compete, as there's no partner for the bottom rung, which is statistically not true for women. It creates a bias to compete, also in evolutionary terms, which may have caused men to evolve to become physically stronger (an important trait for competition in the last 300 thousand years), and to become biologically or perhaps just culturally geared towards competition.

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I understand this is a super black & white view of the world that enormously simplifies a much more complex world. But I do wonder if this birth ratio difference is one of the drivers of the physical, biological and cultural differences we see (on average) across genders. Would be cool to see a sci-fi show which explores different birth ratios (e.g. 60/40 or 40/60), and what effect that would have on via evolution on biology, and on culture.

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Hamiltoned t1_jdr6758 wrote

Or those 200+ million men fuck each other instead of women because non-hetero sexuality is a trait that survived in our evolution because it allows for an even higher % of the population to function as a non-competing component of the tribe.

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somekennyguy t1_jdqm0i4 wrote

So, old story my dad told me. Not 100% on the accuracy, but basically if you want a male, wait and let the male spermies accumulate before attempting. While there are less of them, they typically swim faster and waiting for a bit gives a chance for them to accumulate to sway the odds. If you want a female, just keep going at it. Body produces more female sperm so chances are higher for this outcome. Evolution wise I guess it would make sense as you need more hosts than seed slingers...

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hestermoffet t1_jdqstzz wrote

Extra males are for being just a little homo with the bros

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venity_ t1_jdxhm6h wrote

So king Henry VIII beheading all those women who wouldn't give him a son is because of his own fault?

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artaig t1_jdqexuh wrote

"Most likely"? It's the male who determines whether the offspring is male or female, or are you trying to say something else?

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hpisbi t1_jdqk78v wrote

there are some other theories, including that Y chromosome sperm swim slightly faster than X chromosome sperm or that female embryos have a slightly higher chance of miscarrying. so they’re saying that the current view is that the ratio of X and Y sperm produced is what makes the difference, not the other theories.

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crazyhadron t1_jdqgmxj wrote

Probably because rearing a male child takes way more resources than a female child, so a woman's body would generally abort a male fetus if she was starving and unable to bear the burden.

In modern times, due to access to far better nutrition, this innate adaptation has swung the other way.

Nah, I'm just talking out of my ass.

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Ecstatic-Minimum7088 t1_jdpsxyh wrote

So your saying theres only 2 genders.....

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TerribleHostage t1_jdq3sqd wrote

Sex and gender are different things. Not a fan of inventing new genders every Tuesday though

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MyMudEye t1_jdpurzu wrote

Men universally have a shorter life span than women.

This is due to a number of factors, not least that males make a lot of dumb decisions.

The fact that men are the dominant species may explain the current state of the planet.

I could be wrong, but as a male, I think I'm right.

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LightningOW t1_jdpz7er wrote

You are implying that men and women are different species

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MyMudEye t1_jdq565h wrote

Implying?

Sadly, there are many enforced differences between the sexes. Stud and slut describe the same actions but do not convey the same meaning.

We are still debating skin colour with people who should have gone extinct by now.

We still have people basing their world view on a bronze age interpretation of life, the universe and everything.

Facist religious dogma is inherently sexiest first and foremost. Then comes the racism.

I pick on religion because it is the gateway drug for inequities.

Hail Satan

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