“I Didn’t Have To Embarrass Him Like That”: Wife Tells Husband The Reason They Keep Having Girls
For pregnant couples, the most important thing is usually that a baby is healthy, whether it’s a boy or a girl. But some parents do hope for one or the other, especially if they already have a few kids of the same sex.
This redditor’s husband—a soon-to-be-dad to their third daughter—admitted being a little disappointed that the third bundle of joy wasn’t going to be a boy. However, he wasn’t surprised as he believed that it was related to his wife having three sisters. Little did he know that he was in fact the one determining the sex of the baby.
Seeking to learn more about how the sex of the child is determined, Bored Panda got in touch with a lecturer at the University of Waterloo, expert in Biomedical Science, Dr. Heidi Engelhardt, who was kind enough to answer a few of our questions. Scroll down to find her insight in the text below.
Waiting to learn the sex of your baby can be an exciting time
Image credits: voronaman111 / Envato (not the actual photo)
This man was shocked to learn that it’s the father who determines the sex of the baby
Image credits: Gustavo Fring / pexels (not the actual photo)
Image source: MaleficentType4187
The sex of the child is determined by the chromosomes passed down from the parents
Image credits: MART PRODUCTION / pexels (not the actual photo)
While wishing to have a boy after two daughters in no way means that a parent would love the little one any less if they were a girl, the OP’s husband didn’t hide his disappointment upon learning the sex of their child. Neither did he hide the frustration when his wife tried explaining to him that it has nothing to do with her having three sisters or his mom growing up surrounded by brothers; it is determined by the chromosome passed down from the father.
“Speaking broadly, the male does determine the sex of the child. Getting more specific, it is which of the male’s sperm—of the 500 million or so in that ejaculate—that wins the race to fertilize the oocyte (egg),” Dr. Heidi Engelhardt explained.
“Each sperm has 23 chromosomes (unpaired), chromosomes 1-22 and the sex chromosome. The sex of the child will depend on whether the egg was fertilized by a sperm containing a Y chromosome or an X chromosome.
“The Y chromosome contains a gene, SRY (sex-determining region Y gene), that codes for a master transcription factor (regulator of expression of other genes),” the expert in biomedical science continued. “When SRY turns on (a bit after 6 weeks gestation in humans), it sets off a developmental pathway that transforms the bipotential (generic) fetal gonad into a testis. Products of the testes then drive the development of the rest of the male reproductive tract.”
The sex of the baby is a matter of chance
Image credits: Jonathan Borba / pexels (not the actual photo)
The OP’s husband wasn’t convinced by his wife when she said it was the man who determines the sex of the baby, which is why he turned to his mother—someone with a degree in biology—to see if she was right. He likely came to regret it soon after, as his mom seconded his wife. She also added that it’s not a 50/50 chance—according to the World Health Organization, the natural sex ratio at birth is about 105 boys to every 100 girls.
But regardless of what the ratio is, it always remains a matter of chance, as you can never know for sure if it’s going to be a boy or a girl, even if you already have several children of the same gender. “Thinking it is any different is like expecting to roll a six because you haven’t rolled one in a while, as if you are ‘owed’ a six,” Dr. Engelhardt compared.
The expert revealed that it’s impossible to determine how likely a couple is to have a boy or a girl before they get pregnant; not without assisted reproductive technology (ART), at least. “With various ART procedures (lots of technology), it is possible to [use] in vitro fertilization (IVF)—let the embryos develop in the lab for a week or so, pull off a few cells from each for genetic testing (looking for the SRY gene), and only put a male embryo into the mother’s uterus for development. Then you would be 100% likely to have a male child, barring lab error,” Dr. Engelhardt explained.
“These technologies can be used to avoid having a child with a serious hereditary sex-related disease. Sex selection for non-medical reasons, ‘family balancing’ or social/cultural preferences, is controversial,” she added. “With the exception of the United States, non-medical sex selection is forbidden by law or policy in all countries with laws and policies regulating these procedures.”
If you’re wondering how many bundles of joy who came into this world recently were male or female at birth, in 2023, for instance, there were a total of 134,279,612 babies born across the globe, 32,662,050 of whom were male and 28,098,100 female.
People in the comments shared their opinions, they did not think the redditor was being a jerk to her husband
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The most concerning thing here is how the husband treats having a son as some sort of special achievement that he must get at any cost.
Often men like having a boy to relate to like going to football games etc. However, one of my female friends has 3 daughters, two of which are even more into the football than their dad :). It is not the gender of your children that determine your relationships.
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If I were OP, the child I was carrying would be my last with that guy. Apparently he wasn't paying attention in biology class when they were studying genetics. I also suspect that if they were to decide to have yet another child who turns out to be a boy, the girls are going to be neglected by their dad. It happened in my household growing up, and the favoritism eventually came back to bite my dad in the kiester.
What happened? Just out of curiosity. My mother really wanted a girl, but she got two boys and me. I was the favorite. I watched her abuse. I felt extremely guilty. I feel like all the retaliatory words and actions against me were all my fault. I never wanted this. My mother now has no contact with all four of her children, she’s a d**g addict with no support from her family, and she’s often getting in trouble.
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Please everyone, take off your rose-colored glasses and have a really good look at your partner BEFORE you scramble your DNA together - I am betting my right hand that this is not the first time this person is being an illogical AH who reacts badly to losing an argument
Sperm determining the sex of the offspring is basic middle school science. You learn XY vs XX in 6th grade, if not earlier. Sure you are usually in high school before they talk about other combinations than XX or XY, but the basics are basic. His willful ignorance is a huge red flag and nothing he is reported to have said does anything but ring the alarm bells louder. Great if this is what gets OP out of a bad marriage, but this is probably not the first time he's invented a new reality where science and logic don't apply. Folks, red flags mean danger, stop scrambling your DNA with hysterical misogynists.
This level of stupidity nauseates me. I would be physically unable to have sex with a man who did not know this basic bit of biology.
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Wow, the guy is an AH, first he blames his wife for having girls. Then he blames her for "embarassing him" when he gets corrected by his own mother for a stupid question that he himself asked her. 🤦♀️
In the words of Inspector Harry Callaghan, "A man's got to know his limitations". If you are ignorant about a subject, don't try to pretend you know it.
That's Dirty Harry (Clint Eastwood) espousing one of the most fundamental epistemological principles explained by many philosophers such as Socrates and Lao Tsu- being aware that no matter how much we think we know, there is a vastly greater amount that we don't know.
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On a lighter note /some comic relief for your husband, maybe that info helps your husband overcoming his biology-dyslexia: and deep, profound grief over his "shortcomings"/s: Here in Germany we have a proverb about the sex of your offspring: "Jungs machen Jungs, Männer machen Mädchen."= " Boys make boys, (grown) men make girls." (Source: My dad, proud father of 3 girls cited this to a father of four girls. Made him instantly beam veeeeery bright.)
There was a study in 2020 for "birth sex ratio in the offspring of professional male soccer players" that showed a higher percentage of girls born to male professional athletes(around 30% more likely) with the intensity of training increasing the pecentage divide between them. Small sample size so take it with a grain of salt. At the end of the day who cares, just love them.
Load More Replies... What's it with those dudes that need to have a son? I understand that people who have a lot of children, like not 2 or 3, but 7 or so, might prefer them being mixed, for ... several reasons. But ... why prefer one at all, anyway? If I was to have children, I'd prefer them being healthy, and anything else ... will have to be adressed then, yeah, but ... I just don't see why I would have any preference. Easy to say for a childless guy, I know, but if I suspend me being convinced not to have any, and then think it through as realistic as I could, ... I don't have a preference other than healthy. I get the feeling that those boy-craving guys, and the guys being embarrassed by themselves, yet blaming somebody else (regardless of it being spouse, parents (own, IL), siblings, ...), might share a few traits with the selfproclaimed Alphas. Oh my, is my life easy, the closest to children I ever want to have is cats. Male and deballed, female and deuterussed, but, most important, happy ones.
How does that belief persist? You need a Y chromosome to pass a Y chromosome on. If the offspring consistently lack a Y chromosome, that's on the parent who was contributing (or trying to contribute) it.
Is no one going to say the joke? Male sperm are faster but don't have much stamina, female sperm are slower but have stamina. So the joke was that if females are the ones making it to the egg it's because it's a longer distance... meaning a shorter d**k. If you are only having girls, you have a little d**k. (Might regret posting this later. 🤷🏿)
Right?! This is what I was thinking the whole time. I’m not sure if that’s a myth, but I’ve read that and deduced that boys get more likely if the sperm gets injected…closer to the goal because it can reach that far lol. 😂If that is true, I guess I can see why his fragile little ego got so butt-hurt, but that just makes me laugh more at the FAFO of talking out of you a** in the first place 🤣
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She's NTA, her husband is a huge a$$hole, and she evidently may be more correct than she realizes. A man can have three girls in a row by chance - if it was perfectly by chance, one eighth of all couples who have three kids would have three girls in a row. However, there is evidence that men don't produce sperm at a 50:50 ratio, but some produce more sperm with X chromosomes, and some men produce more sperm with Y chromosomes. So not only do his sperm determine the sex of the baby, but his body is the one which determines whether the baby is more likely to be a boy or a girl. Personally, I am very happy that we had a girl, and I would have preferred that all our kids would be girls. I really shudder at the idea of having a mini-me, or having kids like my brothers. Also, biologically speaking, a daughter carries more of their father's DNA than a son (that Y-chromosome is pretty small and miserable).
Was he this pathetic when she was dating him? Or did his true colors come out after the wedding?
I just hope that OP didn't get pregnant 3 timed because of her babyman's desire to have a son. My bf and I really wanted a son, had the name ready and everything. But we have 3 girls and they are just as awesome as any boy would be. Perhpas we'll get a pet some day with thd boy-name we like. It'd be nice.... depending on what animal it is. Lol.
What’s wrong with having girls? Girls are amazing. Why is having a SON the end all abs be all. It’s so stupid. Sexism behind even before girls are BORN. It’s so sick.
His mom is wrong too. Yes the man determines the sex as it is the sperm who carries the Y chromosome (women only have x) but it is not "the more you have of one sex the more likely the other is the other one". That is not how statistics works.
I don't think the mum was saying that the sex of one child influences the sex of the following children. I think she was saying that if a man as several daughters, then there is a significant chance that he is a man who produces lots of X sperm, and therefore the chances of him having more daughters is quite high.
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I would be sad to realize I was married to someone this profoundly stupid, and not just profoundly stupid, aggressively stupid. This is something that could easily be looked up on Google these days, so what's his excuse for being an ignorant ah? Then when his profound stupidity is revealed, he acts like a toddler. I guess we can be reassured by the fact that intelligence comes up the maternal line so at least there's hope for the children.
She may not have a son, but she's got four children, and one is a pathetic little boy. She's NTA, but she's nuts for sticking with that man-child.
I thought she was going to bring up the fact that bigger dïcks make more sons.
First, it’s amazing how many men are uneducated about basic human biology, something we all had to learn in school. Second, the sex of the baby is inconsequential compared to the health and happiness of that child. Misogyny unfortunately is alive an well and is like a cancer on society, especially women.
There ARE things which are related to birth order and gender, like third sons being LGBTQIA about 50% versus 10% on any other, or if both parents are left handed the kid has a 20% chance of being a lefty (versus 5% if both are righties). Having said that, that breeder male is clueless about genetics. I'll bet he claims "the clitoris is a myth".
Phun Phact: Women CAN pee their names in the snow, just not as quickly.
So he started out blaming her (apparently trying to embarrass her in the process). She pointed out, in private, his ignorance. He then asks his own mother, who confirms he was ignorant and his wife was correct. And now he feels embarrassed by his own ignorance being called out, all on his own, but blames his wife. Yeah. I guess that makes sense. He's already shown he's not especially bright. So this seems reasonable. She is the AH for having kids with a moron.
While there are studies that show many factors in sex ratio, it's important to note they are talking about a small deviation over a large population. The huge jump in male birth ratio in Europe after WWII, was only 51.5% to 49.5%, so 2 out of 100. It may be statistically significant for a country, but for a family, the meaningful ratio is still about 50/50. I also want to point out that none of the factors are choice related, but genetic and environmental, so blaming the wife is inaccurate on several levels. Acting like a child when mother gives out more incorrect info only confirms he's an AH. There's a theory that men have a gene that can predispose them to siring male or female offspring, but no conclusive research. https://www.ncl.ac.uk/press/articles/archive/2015/08/boyorgirlitsinthefathersgenes.html#:~:text=Men%20determine%20the%20sex%20of,make%20a%20boy%20(XY).
ESH. At least factually impaired and judgmental. The notion that it's either person's "fault" is reprehensible. There is nothing about either parent causing daughters. It's a coin toss and 1 in 8 people will have three daughters before having any sons based purely on coin-toss math. I guarantee that the guy is producing 100 million male sperm and 100 million female sperm. (There's a slight chance that there's some rare Y-linked genetic condition that makes male sperm less likely to survive, but that's statistically insignificant.) OP is probably attributing it to the father because it's the sperm which can vary between being male and female, but then again it's the ovum that chooses which of the thousands upon thousands of sperm that reach it gets received inside it.
So, if I understand this correctly, i$ your dad didn't father any boy children, then you won't either? ;)
It's weird to stress about a child's sex. But all things being equal, if I weren't choosing my child through adoption, I'd want the child to be male because it's better to have male privilege working for you than against you. It wouldn't make a huge difference, but I'd want every advantage in the world for my kid, and better pay, being believed by doctors, less chance of a partner murdering them. I'd love a girl just the same, but it's easier (not easy) to be part of the group that considered "normal" in most studies.
HE asked HIS MOTHER a stupid question and somehow it's his wife's fault even though she told him he was wrong beforehand... It's a pity they're on their third child because this guy is not a keeper.
Sounds like Real Men have sons! Plus he has some competition with his brothers going on in his head.
Middle school health class teaches this, then taught again in high school biology.
The fun part is of course that the argument "It's the sperm which determines the gender" is only part of the story --- because he is basically accusing the female body of rejecting male sperm & only incubating female sperm. This is NOT far-fetched, there is over 200 species of mammals which selectively bias the son/daughter ratio depending on circumstances! [e.g., https://theconversation.com/mammalian-mums-control-the-sex-of-their-offspring-15975 or more fun https://academic.oup.com/biolreprod/article/71/4/1063/2666975 ] In humans, we know the female body selectively aborts female fetuses more often (that's why there's more males at birth); we know the female sperm swims slightly slower; we know father's hormone levels can change the ratio male:female of his sperm. His base argument (she has sisters therefore daughters) is of course wrong, there is no inheritable sex ratio bias [ https://royalsocietypublishing.org/doi/10.1098/rspb.2019.2849 ].
There is also the fact that the mother can carry mutations on their xx chromosomes that are lethal. Different mutations on each so they balanced, but when one x is matched with the y from the father, the fœtus is not viable. Genetics is a fun science.
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The most concerning thing here is how the husband treats having a son as some sort of special achievement that he must get at any cost.
Often men like having a boy to relate to like going to football games etc. However, one of my female friends has 3 daughters, two of which are even more into the football than their dad :). It is not the gender of your children that determine your relationships.
Load More Replies... If I were OP, the child I was carrying would be my last with that guy. Apparently he wasn't paying attention in biology class when they were studying genetics. I also suspect that if they were to decide to have yet another child who turns out to be a boy, the girls are going to be neglected by their dad. It happened in my household growing up, and the favoritism eventually came back to bite my dad in the kiester.
What happened? Just out of curiosity. My mother really wanted a girl, but she got two boys and me. I was the favorite. I watched her abuse. I felt extremely guilty. I feel like all the retaliatory words and actions against me were all my fault. I never wanted this. My mother now has no contact with all four of her children, she’s a d**g addict with no support from her family, and she’s often getting in trouble.
Load More Replies... Please everyone, take off your rose-colored glasses and have a really good look at your partner BEFORE you scramble your DNA together - I am betting my right hand that this is not the first time this person is being an illogical AH who reacts badly to losing an argument
Sperm determining the sex of the offspring is basic middle school science. You learn XY vs XX in 6th grade, if not earlier. Sure you are usually in high school before they talk about other combinations than XX or XY, but the basics are basic. His willful ignorance is a huge red flag and nothing he is reported to have said does anything but ring the alarm bells louder. Great if this is what gets OP out of a bad marriage, but this is probably not the first time he's invented a new reality where science and logic don't apply. Folks, red flags mean danger, stop scrambling your DNA with hysterical misogynists.
This level of stupidity nauseates me. I would be physically unable to have sex with a man who did not know this basic bit of biology.
Load More Replies... Wow, the guy is an AH, first he blames his wife for having girls. Then he blames her for "embarassing him" when he gets corrected by his own mother for a stupid question that he himself asked her. 🤦♀️
In the words of Inspector Harry Callaghan, "A man's got to know his limitations". If you are ignorant about a subject, don't try to pretend you know it.
That's Dirty Harry (Clint Eastwood) espousing one of the most fundamental epistemological principles explained by many philosophers such as Socrates and Lao Tsu- being aware that no matter how much we think we know, there is a vastly greater amount that we don't know.
Load More Replies... On a lighter note /some comic relief for your husband, maybe that info helps your husband overcoming his biology-dyslexia: and deep, profound grief over his "shortcomings"/s: Here in Germany we have a proverb about the sex of your offspring: "Jungs machen Jungs, Männer machen Mädchen."= " Boys make boys, (grown) men make girls." (Source: My dad, proud father of 3 girls cited this to a father of four girls. Made him instantly beam veeeeery bright.)
There was a study in 2020 for "birth sex ratio in the offspring of professional male soccer players" that showed a higher percentage of girls born to male professional athletes(around 30% more likely) with the intensity of training increasing the pecentage divide between them. Small sample size so take it with a grain of salt. At the end of the day who cares, just love them.
Load More Replies... What's it with those dudes that need to have a son? I understand that people who have a lot of children, like not 2 or 3, but 7 or so, might prefer them being mixed, for ... several reasons. But ... why prefer one at all, anyway? If I was to have children, I'd prefer them being healthy, and anything else ... will have to be adressed then, yeah, but ... I just don't see why I would have any preference. Easy to say for a childless guy, I know, but if I suspend me being convinced not to have any, and then think it through as realistic as I could, ... I don't have a preference other than healthy. I get the feeling that those boy-craving guys, and the guys being embarrassed by themselves, yet blaming somebody else (regardless of it being spouse, parents (own, IL), siblings, ...), might share a few traits with the selfproclaimed Alphas. Oh my, is my life easy, the closest to children I ever want to have is cats. Male and deballed, female and deuterussed, but, most important, happy ones.
How does that belief persist? You need a Y chromosome to pass a Y chromosome on. If the offspring consistently lack a Y chromosome, that's on the parent who was contributing (or trying to contribute) it.
Is no one going to say the joke? Male sperm are faster but don't have much stamina, female sperm are slower but have stamina. So the joke was that if females are the ones making it to the egg it's because it's a longer distance... meaning a shorter d**k. If you are only having girls, you have a little d**k. (Might regret posting this later. 🤷🏿)
Right?! This is what I was thinking the whole time. I’m not sure if that’s a myth, but I’ve read that and deduced that boys get more likely if the sperm gets injected…closer to the goal because it can reach that far lol. 😂If that is true, I guess I can see why his fragile little ego got so butt-hurt, but that just makes me laugh more at the FAFO of talking out of you a** in the first place 🤣
Load More Replies... She's NTA, her husband is a huge a$$hole, and she evidently may be more correct than she realizes. A man can have three girls in a row by chance - if it was perfectly by chance, one eighth of all couples who have three kids would have three girls in a row. However, there is evidence that men don't produce sperm at a 50:50 ratio, but some produce more sperm with X chromosomes, and some men produce more sperm with Y chromosomes. So not only do his sperm determine the sex of the baby, but his body is the one which determines whether the baby is more likely to be a boy or a girl. Personally, I am very happy that we had a girl, and I would have preferred that all our kids would be girls. I really shudder at the idea of having a mini-me, or having kids like my brothers. Also, biologically speaking, a daughter carries more of their father's DNA than a son (that Y-chromosome is pretty small and miserable).
Was he this pathetic when she was dating him? Or did his true colors come out after the wedding?
I just hope that OP didn't get pregnant 3 timed because of her babyman's desire to have a son. My bf and I really wanted a son, had the name ready and everything. But we have 3 girls and they are just as awesome as any boy would be. Perhpas we'll get a pet some day with thd boy-name we like. It'd be nice.... depending on what animal it is. Lol.
What’s wrong with having girls? Girls are amazing. Why is having a SON the end all abs be all. It’s so stupid. Sexism behind even before girls are BORN. It’s so sick.
His mom is wrong too. Yes the man determines the sex as it is the sperm who carries the Y chromosome (women only have x) but it is not "the more you have of one sex the more likely the other is the other one". That is not how statistics works.
I don't think the mum was saying that the sex of one child influences the sex of the following children. I think she was saying that if a man as several daughters, then there is a significant chance that he is a man who produces lots of X sperm, and therefore the chances of him having more daughters is quite high.
Load More Replies... I would be sad to realize I was married to someone this profoundly stupid, and not just profoundly stupid, aggressively stupid. This is something that could easily be looked up on Google these days, so what's his excuse for being an ignorant ah? Then when his profound stupidity is revealed, he acts like a toddler. I guess we can be reassured by the fact that intelligence comes up the maternal line so at least there's hope for the children.
She may not have a son, but she's got four children, and one is a pathetic little boy. She's NTA, but she's nuts for sticking with that man-child.
I thought she was going to bring up the fact that bigger dïcks make more sons.
First, it’s amazing how many men are uneducated about basic human biology, something we all had to learn in school. Second, the sex of the baby is inconsequential compared to the health and happiness of that child. Misogyny unfortunately is alive an well and is like a cancer on society, especially women.
There ARE things which are related to birth order and gender, like third sons being LGBTQIA about 50% versus 10% on any other, or if both parents are left handed the kid has a 20% chance of being a lefty (versus 5% if both are righties). Having said that, that breeder male is clueless about genetics. I'll bet he claims "the clitoris is a myth".
Phun Phact: Women CAN pee their names in the snow, just not as quickly.
So he started out blaming her (apparently trying to embarrass her in the process). She pointed out, in private, his ignorance. He then asks his own mother, who confirms he was ignorant and his wife was correct. And now he feels embarrassed by his own ignorance being called out, all on his own, but blames his wife. Yeah. I guess that makes sense. He's already shown he's not especially bright. So this seems reasonable. She is the AH for having kids with a moron.
While there are studies that show many factors in sex ratio, it's important to note they are talking about a small deviation over a large population. The huge jump in male birth ratio in Europe after WWII, was only 51.5% to 49.5%, so 2 out of 100. It may be statistically significant for a country, but for a family, the meaningful ratio is still about 50/50. I also want to point out that none of the factors are choice related, but genetic and environmental, so blaming the wife is inaccurate on several levels. Acting like a child when mother gives out more incorrect info only confirms he's an AH. There's a theory that men have a gene that can predispose them to siring male or female offspring, but no conclusive research. https://www.ncl.ac.uk/press/articles/archive/2015/08/boyorgirlitsinthefathersgenes.html#:~:text=Men%20determine%20the%20sex%20of,make%20a%20boy%20(XY).
ESH. At least factually impaired and judgmental. The notion that it's either person's "fault" is reprehensible. There is nothing about either parent causing daughters. It's a coin toss and 1 in 8 people will have three daughters before having any sons based purely on coin-toss math. I guarantee that the guy is producing 100 million male sperm and 100 million female sperm. (There's a slight chance that there's some rare Y-linked genetic condition that makes male sperm less likely to survive, but that's statistically insignificant.) OP is probably attributing it to the father because it's the sperm which can vary between being male and female, but then again it's the ovum that chooses which of the thousands upon thousands of sperm that reach it gets received inside it.
So, if I understand this correctly, i$ your dad didn't father any boy children, then you won't either? ;)
It's weird to stress about a child's sex. But all things being equal, if I weren't choosing my child through adoption, I'd want the child to be male because it's better to have male privilege working for you than against you. It wouldn't make a huge difference, but I'd want every advantage in the world for my kid, and better pay, being believed by doctors, less chance of a partner murdering them. I'd love a girl just the same, but it's easier (not easy) to be part of the group that considered "normal" in most studies.
HE asked HIS MOTHER a stupid question and somehow it's his wife's fault even though she told him he was wrong beforehand... It's a pity they're on their third child because this guy is not a keeper.
Sounds like Real Men have sons! Plus he has some competition with his brothers going on in his head.
Middle school health class teaches this, then taught again in high school biology.
The fun part is of course that the argument "It's the sperm which determines the gender" is only part of the story --- because he is basically accusing the female body of rejecting male sperm & only incubating female sperm. This is NOT far-fetched, there is over 200 species of mammals which selectively bias the son/daughter ratio depending on circumstances! [e.g., https://theconversation.com/mammalian-mums-control-the-sex-of-their-offspring-15975 or more fun https://academic.oup.com/biolreprod/article/71/4/1063/2666975 ] In humans, we know the female body selectively aborts female fetuses more often (that's why there's more males at birth); we know the female sperm swims slightly slower; we know father's hormone levels can change the ratio male:female of his sperm. His base argument (she has sisters therefore daughters) is of course wrong, there is no inheritable sex ratio bias [ https://royalsocietypublishing.org/doi/10.1098/rspb.2019.2849 ].
There is also the fact that the mother can carry mutations on their xx chromosomes that are lethal. Different mutations on each so they balanced, but when one x is matched with the y from the father, the fœtus is not viable. Genetics is a fun science.
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