it almost seems to me (at least in North America) that for every boy-girl sibling combination, the boys is born first more often than not. is this a statistical fact? are boys born first more often? or are they born with the same frequency as males within the entire population?
i am a boy and i was first born. my dad was first born, so was my mum, my dad’s mum was first born and so was my dad’s dad, not sure about my mum’s parents.
You’re generalizing from limited evidence. My father’s family had a firstborn daughter. My sister was the firstborn. My daughter was the firstborn. My wife was the firstborn. My mother in law was the firstborn.
The proportion of male live births to females is just slightly over 1:1. I haven’t seen any evidence that suggests that proportion is any different depending on birth order.
I do know of a number of families that quit having kids after they had a boy, so if anything, I’ll bet the percentage of LAST born boys is higher, or even more significantly, the number of last born children who are a different sex than their siblings.
I’ve read (sorry, no cite - it was a long time ago), that accidental pregnancies are more often girls, and planned are more often boys - and overall, there are slightly more boys than girls.
The claim was that ‘male sperm’ are typically faster, but less durable than ‘female sperm.’ So birth control is typically more effective against male sperm.
Why is this relevant? I think there’s probably a positive correlation between first pregnancies and accidental pregnancies; thus, if what I’ve posted here is true, there would be more first-born daughters in the general population.
yeah it’s true about the sperm thing. the Y sperm (the one that’ll make a male baby) is a bit like a sprinter really, it’ll get to the egg first if there is one available at the time, but if they have to wait around for the egg to arrive, the Y sperm lose energy and the long distance X sperm have a higher chance of fertilising.
if you have sex every night a male baby is more likely as there will always be fresh Y sperm swimming about. if you have sex less often the X sperm will be more likely to fertilise unless you have sex at exactly the right time.
In the US of A there are 105 male births for every 100 female births. This would skew the likelihood of the 1st birth being male, as well as the 2nd, 3rd,…
Niobium Said: yeah it’s true about the sperm thing. the Y sperm (the one that’ll make a male baby) is a bit like a sprinter really, it’ll get to the egg first if there is one available at the time, but if they have to wait around for the egg to arrive, the Y sperm lose energy and the long distance X sperm have a higher chance of fertilising.
Niobium what are you basing your statistics on? Just because an egg is available at the time of ejaculation does not mean that the sperm carrying the male chromosomes will get there first. I agree there may be some science to it, but it isn’t quite as simple as you make it seem.
My family, (both mother’s and father’s sides) have had first born boys foe several generations. The exception is my father’s brother, he has a first born daughter.
I’m willing to bet it’s 50.1% one way, 49.9% the other.
I don’t see how the rate is different for first born than any other number. They are exclusive of each other. The odds are the same that baby #9 will be a boy after 8 girls as they are if after 8 boys.
More boys are born than girls There is no debate on that fact. It is said that the reason is that girls from birth to old age have greater survivalability than boys and therefor the need for more boys in this world initially. As a result, there would probably be a greater no. of first born males than females.
I always thought it was the other way around. There were more girls born in the world than boys.
kertang i did not say that. i said the male one will have a higher chance of fertilising the egg. it is that simple, trust me i read it in Scientific American
no, think about it. boys go to war and get killed, girls dont.
it is interesting that every time there has been a large war with lots of men getting killed, the proportion of men to women finds it’s way back to 50/50 quite quickly. this is cos of that sperm thing. when the men come back from war they have sex often and ends up more boys are born than girls.
not sure about the original question about first borns more likely to be male, except perhaps couples have sex more often at the start of their relationships and so boys are more likely? it’s possible.
MadSam is right: more boys are born than girls. What I find suprising, more boys are conceived than girls, in the ratio of 1.25/1.
But male births are decreasing, and some scientists are concerned that this heralds an early warning of significantly deleterious environmental events.
Check out this brief Scientific American article or
this more detailed story from Science News.
Selective abortion could of course boost the male birth ratio even higher. That is, Ken and Barbie conceive, find out they will have a girl, curse the gods that have denied them a son, decide to abort. Pretty cold, but I’m sure it happens.
Based upon my (admittedly aged) memory of my Human Life Span Development course at Indiana University (home of the Kinsey Institute), a predictor of the sex of the child is whether and how often the female climaxes during intercourse. The logic is that the “male sperm”, being less durable but faster )or more plentiful, I can’t remember), are more likely to reach the egg first in a “friendly” envirnoment. The instructor stated that the female climax created a more “male sperm”-friendly environment. I won’t dare to offer a conclusion on whether this predicts the proportion of male/female birth rates, but I will admit to using this logic to win two straight office baby pools (intuition).
Based upon my (admittedly aged) memory of my Human Life Span Development course at Indiana University (home of the Kinsey Institute), a predictor of the sex of the child is whether and how often the female climaxes during intercourse. The logic is that the “male sperm”, being less durable but faster )or more plentiful, I can’t remember), are more likely to reach the egg first in a “friendly” envirnoment. The instructor stated that the female climax created a more “male sperm”-friendly environment. I won’t dare to offer a conclusion on whether this predicts the proportion of male/female birth rates, but I will admit to using this logic to win two straight office baby pools (intuition).
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[Edited by bibliophage on 11-09-2001 at 07:49 AM]