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AstroChuck's avatar

Are boy embyos or fetuses sturdier than girl ones?

Asked by AstroChuck (36634 points ) March 20th, 2009 from iPhone

There is exactly a 50% chance of a father passing an x chromosome as a y, yet there are slightly more boys born into this world than there are girls. In spite of this there are more women on this planet than men. We know that females are built sturdier as they out live men. I would imagine that has something to do with having to withstand pregnancy and childbirth.
So why the higher male birthrate?

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18 Answers

SpatzieLover's avatar

Male fetuses and infants also have a higher death rate, Astro. I think it’s Mother Nature’s way of making certain the population keeps going.

eponymoushipster's avatar

nature finds a way.

casheroo's avatar

I’m trying to find this article from Mental Floss, about how geez, I think the male (possibly female..50/50 chance) is going extinct. I think it’s the male.
This says most males are miscarried though http://www.mentalfloss.com/blogs/archives/17957
It’s really bothering me that I can’t find the article.

tinyfaery's avatar

I believe more male fetuses are spontaneously aborted. Something about the womb enviornment is detrimental to male fetuses.

asmonet's avatar

I always heard we had more women because we tend to send the boys off to war.
That at least explains the adult population differences. Sorta?

A_Beaverhausen's avatar

what a great question!

asmonet's avatar

I don’t know what an embyo is, Chuckie.

Harp's avatar

Male fetuses grow considerably faster during the first trimester than do females. Toward term, though, the difference levels off.

It has been suggested that the in utero growth rate may actually be a factor in the disease susceptibility and earlier onset of senescence in adult males.

AstroChuck's avatar

@Harp- So perhaps in the zygote stage the female is more likely to be miscarried?

@casheroo- I know what you are referencing, and I know that males are ultimately doomed. That, however, is an entirely different thing.

nikipedia's avatar

@AstroChuck: Great question. As far as I know, this is a pretty complicated problem, and I think the human sex ratio imbalance has yet to be sorted out.

I have a book at home that might be able to answer these questions better as I’m having trouble gaining access to relevant articles, but I believe that male embryos are hypothesized to actually be weaker than female embryos. My understanding is that the likelihood of getting an X versus a Y is not, in fact, exactly equal, so you start off with a bunch of extra boys at conception and they slowly die off throughout life. (Yikes!)

Here’s a bit from the encyclopedia brittanica (although I want to point out that they do NOT cite their sources, unlike wikipedia!):

Studies indicate that male embryos suffer a relatively greater degree of prenatal mortality, so that the sex ratio at conception might be expected to favour males even more than the 106 : 100 ratio observed at birth would suggest. Firm explanations for the apparent excess of male conceptions have not been established; it is possible that Y-containing sperm survive better within the female reproductive tract, or that they may be a little more successful in reaching the egg in order to fertilize it. In any case, the sex differences are small, the statistical expectation for a boy (or girl) at any single birth still being close to one out of two.
http://www.britannica.com/EBchecked/topic/228983/human-genetics/50732/Fertilization-sex-determination-and-differentiation

AstroChuck's avatar

@nikipedia- That’s something I hadn’t considered. I could see where the sperm carrying a y chromosome could be sturdier. That would explain everything.

SeventhSense's avatar

@AstroChuck
Sounds like nature’s way of compensating for the greater mortality rate of men at a younger age than women.

nikipedia's avatar

@AstroChuck: X or Y? The Y is a teensy fragile little sucker—but then again, he might be just a hair faster because of it.

SeventhSense's avatar

@SpatzieLover
I think I we just orgasmed..

AstroChuck's avatar

@asmonet- edit: embryo.
After I ask a question I always go back and correct typos. On this question I think I went back about four times and I still didn’t catch that. Duh. Now you know why I’m just a lowly civil servant.

asmonet's avatar

It’s cool, it’s not like we pay you real money. I pay you in lollipops remember? ;)

galileogirl's avatar

Let’s get this straight:

Male fetuses are more fragile than females.

Male children, adolescents and young adults are such foolish risktakers that they have higher accidental death rates

Adult men have such unhealthy lifestyles that they have a lower life expectancy

And for thousands of years WOMEN were called the weaker sex.

Thank Goddess, we’ve finally gotten it right.

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