What determines the sex of your child?

This thread is a spin-off from the what percentage of the male population... thread.

A professor at the London School of Economics has blogged that there is a link between tall parents and male offspring. He cites the work of evolutionary biologist Robert L. Trivers and mathematician, Dan E. Willard and their "Trivers-Willard hypothesis".

In a nutshell, the hypothesis states that couples with wealth and status have more sons, while the poor have more daughters. The evolutionary explanation is that the sons inherit wealth and status (desirable traits for attracting mates) from their parents, and have to opportunity to father more children with different partners, while their wealthy daughters have a relatively limited number of offspring.

The poor male is an unattractive mate, and may not reproduce. However, his poor sister still has a chance at being chosen for a mate due to her physical attractiveness. So over time, poor females beget more poor females.

The blogger mentions that there has been an extension of the original hypothesis to a "generalized" hypothesis, that if the parents possess any trait that provides an advantage to offspring of either sex, they will have more children of that gender.

This is why taller parents will tend to have more boys than girls. Height is an advantage for males competing for mates, while it is inconsequential for females. The taller male offspring reproduce more than the tall females, producing taller sons who reproduce more, and so on.

The Questions
1) Were your birth parents tall (compared to their general population)?
2) Including you, did your birth parents have more boys than girls? If you are an only child, please consider yourself a majority.
*** Edit: I forgot to add a "same number of boys and girls" option. If that is your case, please mention it.***




It should be noted that the blogger (Dr. Satoshi Kanazawa) was recently suspended from the London School of Economics over the furor surrounding his blog article stating that research has demonstrated that black women are considered less physically attractive than women of other races, while black men compare favorably. The conclusions were later debunked as based on sketchy data, that was not controlled for the respondent's bias for, or against race. I think this casts a shadow on his tall= increased likelyhood of male offspring hypothesis, but no one has debunked it yet.

Quote: Ayecarumba

1) Were your birth parents tall (compared to their general population)?

Which general population? My parents were taller than average for Mexico, but not for Jews in Poland and Lithuania, were my grandparents came from. In a country witha great deal more, and more recent, immigration like America, the question can be quite ambiguous.

Quote: Ayecarumba

Height is an advantage for males competing for mates, while it is inconsequential for females.

Whaa??? A tall woman is NOT inconsequential to me! I'm 6'2", and the taller the girl is, the better. Dating a short girl is like stealing a potential mate from a short guy who can't get a tall one. Maybe inconsequential to you, but some of us are looking for the tall ones.

Quote: Ayecarumba

The Questions
1) Were your birth parents tall (compared to their general population)?
2) Including you, did your birth parents have more boys than girls? If you are an only child, please consider yourself a majority.

1. Mom died when I was born, so I don't know. Dad is 5'10" or so.
2. I have 2 older sisters, both average height.

I have also heard it's the health of the parents that determines height. Being fit, and passing on good nutritional habits with a full vitamin range can only be helpful.

Also, I've read many gay boys have 2 or more older brothers, the reason being that mothers whose wombs have already birthed a couple sons, now will secrete some kinda enzyme or extra hormones that decreases the likelihood that the third son will compete with the elder two for mates.

Quote: Ayecarumba

... his blog article stating that research has demonstrated that black women are considered less physically attractive than women of other races, while black men compare favorably. The conclusions were later debunked as based on sketchy data,

Sketchy? Like just looking around and seeing who's hot and who's not? I'd rank Brazilian women, Scandinavian women and Asian women near (or at) the top, and the common American black woman near the bottom, mostly due to their thick, fast food BWA and their basic bitchiness, something Brazilian black women lack. So I'd agree with Dr. Kanazawa and applaud him for saying in public what many already feel in private. Someone once also stated that a study was done that proved whites are smarter than blacks, and Asians are smarter than whites. And again, there was public furor even though it's probably true, generally speaking.

Average height but my paternal lineage is full of men.

It would help to prove or disprove this theory if we could see graphs showing height distribution by gender. If it were true you would expect a longer and fatter tail on the tall side for men than women.

Also, if this hypothesis were true, wouldn't the differential between the average height of men and women keep increasing? Then again, maybe women don't find extremely tall men attractive, like over seven feet, keeping that effect in check.

My dad is 6'2", my mom was 5'7"; I'd say that was tall for people born in the '20s.

They had 6 children, 2 boys and 4 girls. I'm 6'2", my brother was 6'3". I have 2 sisters who are 5'10", one who is 5'8" and one who is 5'6".

Among the 6 of us, I'm the only one with children of my own. I have one daughter, she's 5'10".

my father is 6'4" and my mother is 5'8". im 6'4" and my one sibling, my sister, is 5"11. my father had 3 brothers, a half-brother, and a half-sister. my fathers 3 brothers were 6'2", 6'5", and 6'8". my 6'5" uncle has two daughters and one son. the son is 7'2". my 6'8" uncle has one son and one daughter. the son is 6'11".

Quote: Nareed

Which general population? My parents were taller than average for Mexico, but not for Jews in Poland and Lithuania, were my grandparents came from. In a country witha great deal more, and more recent, immigration like America, the question can be quite ambiguous.

Let's go with the general population where you were born.

Quote: Wizard

Average height but my paternal lineage is full of men.

It would help to prove or disprove this theory if we could see graphs showing height distribution by gender. If it were true you would expect a longer and fatter tail on the tall side for men than women.

Also, if this hypothesis were true, wouldn't the differential between the average height of men and women keep increasing? Then again, maybe women don't find extremely tall men attractive, like over seven feet, keeping that effect in check.

I don't want to comment on what I expect from this poll yet. Let's get more data in.

As for the difference in height continuing to increase, I suspect other factors would come into play. You mention a distinct possibility that I would agree with.

Quote: zippyboy

Dating a short girl is like stealing a potential mate from a short guy who can't get a tall one. Maybe inconsequential to you, but some of us are looking for the tall ones.

Hehe. Thanks zippyboy. On behalf of the altitude challenged, we appreciate your consideration.

Seriously, I think the Dr. would say it is inconsequential, since a tall woman could still be as attractive to a short guy (see Anna Nicole Simpson), as a short woman.

Quote: zippyboy

I have also heard it's the health of the parents that determines height. Being fit, and passing on good nutritional habits with a full vitamin range can only be helpful.

Agreed. This would present a problem for the data, as height and nutrition are certainly related. I expect that it would come out in the wash, given enough data points.

Quote: zippyboy

Also, I've read many gay boys have 2 or more older brothers, the reason being that mothers whose wombs have already birthed a couple sons, now will secrete some kinda enzyme or extra hormones that decreases the likelihood that the third son will compete with the elder two for mates.

I've never heard of this. It doesn't make evolutionary sense to me since the reproductive years of a woman are so limited, why would a biological mechanism develop to keep male offspring from fully competing with each other. You would think the strongest competitor would just win out, especially since male mortality is higher.

Quote: rudeboyoi

my father is 6'4" and my mother is 5'8". im 6'4" and my one sibling, my sister, is 5"11. my father had 3 brothers, a half-brother, and a half-sister. my fathers 3 brothers were 6'2", 6'5", and 6'8". my 6'5" uncle has two daughters and one son. the son is 7'2". my 6'8" uncle has one son and one daughter. the son is 6'11".

Bummer, I forgot to add "same number of boys and girls" as a choice. Ooops.

rudeboyoi, does your paternal family tree have more brothers than sisters going back even more generations? I note that your father was born into a family of five boys and one girl. (assuming the half brother and sister were from your grandfather's prior relationship). Even if not, your paternal grandfather had four boys. Do you know how many brothers and sisters he had?

Quote: Mosca

My dad is 6'2", my mom was 5'7"; I'd say that was tall for people born in the '20s.

They had 6 children, 2 boys and 4 girls. I'm 6'2", my brother was 6'3". I have 2 sisters who are 5'10", one who is 5'8" and one who is 5'6".

Among the 6 of us, I'm the only one with children of my own. I have one daughter, she's 5'10".

Thanks Mosca. Were there other siblings who did not survive? This was a common occurence in the pre-pre-natal care war years.

Quote: Ayecarumba

Thanks Mosca. Were there other siblings who did not survive? This was a common occurence in the pre-pre-natal care war years.

Not sure what you mean, so I'll hit them all. My father had no siblings. My mother had a brother, he was average height, maybe 5'9". My mother had one child stillborn; she had 7 pregnancies and 6 children survived. Among all of us, none had any children except me. My oldest sister will be 60 next month, my youngest sister is 50.

Quote: Ayecarumba

Bummer, I forgot to add "same number of boys and girls" as a choice. Ooops.

rudeboyoi, does your paternal family tree have more brothers than sisters going back even more generations? I note that your father was born into a family of five boys and one girl. (assuming the half brother and sister were from your grandfather's prior relationship). Even if not, your paternal grandfather had four boys. Do you know how many brothers and sisters he had?

the half-siblings were on my grandmothers side. i know hardly anything about my grandparents. they all died when i was extremely young. however i just asked my dad though and he said his father was 6'5" and had one sister.

Any other responses? 5 points doth not R-squared make.