Article on single moms and gender.some parts may rub you the wrong way.

[queen-of-harts]

Human evolution
Girl power
Single mothers are more likely to have daughters
Oct 21st 2004 | from the print edition
..ALL over the world, more boys are born than girls. Evolutionary biologists believe that this is because boys (and, indeed, males in general) are more likely to die at a given age than are their female contemporaries. The imbalance at birth thus means that the sex ratio balances at the age when people are reproducing. But for decades there has been a puzzling trend in the boy:girl ratio. In Britain, as well as in the United States and Canada, the proportion of boys being born is dropping. No one knows why, although it has been suggested, somewhat controversially, that the trend is due to chemical pollutants that are mimicking the effects of sex hormones.

And yet there is another recent trend that may have something to do with it. During the same period, the proportion of single mothers has been increasing. The reasons for this are less puzzling, but as the Italian nominee to the European commission, Rocco Buttiglione, found out this week when he apparently suggested that single mothers were not very good as parents, it is no less controversial. The question is, could the two trends be linked? Can household arrangements affect the human sex ratio?

According to Karen Norberg, of the National Bureau of Economic Research in Cambridge, Massachusetts, they can. In a review of data from almost 60,000 American families, Dr Norberg found that the chance of a woman giving birth to a boy rather than a girl is higher if she has been living with a man before the child was conceived. To be specific, for parents who were living together, boys were born 51.5% of the time, while when the parents were not cohabiting only 49.9% of births were male. This difference may seem small, but statistically it is highly significant, which suggests it is the result of evolution. Dr Norberg's paper was published this week in the Proceedings of the Royal Society.
Actually, as with so much else in biology, Charles Darwin got there first. In “The Descent of Man”, he referred to studies showing that among children born out of wedlock there were more girls than boys. Dr Norberg's work reinforces the point, and also shows that it is not formal marriage, but actual cohabitation, that is the decisive factor. What neither Darwin's nor Dr Norberg's work shows, though, is why.




Sons and lovers

There are some clues. In work on other mammals, researchers have found an association between hormones, the frequency of copulation, and the sex of the offspring. In other words, there is a way the body might “know” if it is cohabiting with someone by the amount of sex it is getting, since copulation changes the levels of various hormones. It is also known that a woman's hormonal motivation to have sex is highest on the day of ovulation, and that sex on that day is more likely to result in a girl. Couples who live apart, and therefore probably have intercourse less often, may be more likely to do so when the motivation is highest—resulting in a girl.

This chain of reasoning, though, provides only what workers in the field call a proximate cause. What is needed for a complete explanation is an ultimate—evolutionary—cause.

It is easy to speculate. Perhaps same-sex children are easier for a lone parent to rear. Perhaps parents pass on different kinds of benefits to same-sex offspring and opposite-sex offspring. Perhaps a father helps his son to learn sex-specific skills, as in bird songs. Perhaps boys are simply more costly to raise than girls, and would thus overtax the resources of a lone parent. However, a more controversial possibility is that—in a Darwinian sense only—Mr Buttiglione is right that two parents are sometimes better than one.

It is well established, in both humans and other species, that successful males have lots of offspring, while unsuccessful ones have few or none. Females, by contrast, show a smaller range of reproductive output, with most having some offspring, but none having as many as the most successful males. The upshot is that it makes evolutionary sense to have sons when circumstances favour them becoming big, strong, clever and handsome (and therefore attractive to women), but when they do not, it is better for a woman to have daughters, most of whom will find a mate even in tough times. That way, a woman will maximise the number of grandchildren she has. In the case of humans, circumstances favouring the raising of strong, healthy children could include having two parents around, since humans are unusual among mammals in that fathers are often involved in parental care.

Of course, even if this evolutionary explanation of Dr Norberg's result does turn out to be correct, it probably does not carry any lessons for the modern world. Such biological patterns would have been established hundreds of thousands—or possibly millions—of years ago. Bringing up children alone in a rich, industrialised society is a rather different proposition from bringing them up in a hunter-gatherer band, and there is no reason to suppose they would be at a disadvantage now. Except, perhaps, that with a surplus of women around, it will be even harder than it is today for a girl to find a suitable husband when she grows up.

[atomic sagebrush]

Yeah, I've read this one before and I do find it interesting. This meshes with something that I have observed a lot where there is a single mom/daughter living together even into adulthood...I only know of one single gal with a son and she was with the dad when he was conceived. I am sure there are tons of exceptions.

I just want to point out that several things in the article are rather speculative (such as the "frequency of copulation/sex of offspring" thing which may or may not be true, and the article claims BD on O leads to more girls being born - again, this may or may not be true). Heaven knows that many of us who have been married for like a bazillion years do NOT have sex with any great frequency, as my husband could probably whine about in mind-numbing detail, and yet still seem to churn out boy after boy LOL.....

[lindi]

I am fascinated by the brief mention in this article that cohabitating and frequent sex change the hormonal makeup of the woman- I thought I read that frequent sex for a women raises testosterone. I know when women live together their periods sync, and I wonder if just being a around a man in a living situation is enough to raise T and then esp. with the freqent sex those women would have higher T...the body would sense times are "good" to have a son and adjust accordingly?
I think I also read girls get their first period sooner when there is no man in the house with them. It senses times are tough and that it needs to reproduce sooner for the good of the species because something is amiss.
Maybe to sway girl you need to send DH on a vacation before the attempt? Or better yet go yourself?

[atomic sagebrush]

I am fascinated by the brief mention in this article that cohabitating and frequent sex change the hormonal makeup of the woman- I thought I read that frequent sex for a women raises testosterone. I know when women live together their periods sync, and I wonder if just being a around a man in a living situation is enough to raise T and then esp. with the freqent sex those women would have higher T...the body would sense times are "good" to have a son and adjust accordingly?
I think I also read girls get their first period sooner when there is no man in the house with them. It senses times are tough and that it needs to reproduce sooner for the good of the species because something is amiss.
Maybe to sway girl you need to send DH on a vacation before the attempt? Or better yet go yourself?

There are DOZENS of possible things it could be...planned pregnancies (blue) vs. birth control failures (pink), that being around a woman all the time raises the man's sperm count, even the idea that people who wait to have kids until they are married are somehow different in temperament/hormones to begin with. I hope that no one panics over any speculative ideas because while it's fun and interesting to talk about, all of us are still perfectly capable of conceiving a baby of either gender regardless of our marital status.

The Duggars are extremely stable and they have pretty close to equal numbers of boys and girls.

[maidentomother]

I think living with a man can have an effect on a woman's cycle via pheromones. For 4 months I lived with a good male friend in his studio apartment, even slept in the same bed & cuddled, though our relationship was purely platonic. While living with him my cycle shortened from its 28-days to 21-days! As soon as I moved out it retruned to normal. I have lived in close proximity with other men and none have had this effect on me other than my one friend. He also had a very strong, distinctive scent - not bad, but not appealing either. I always considered pheromones responsible, no sex required!

Still, I don't know how common such a strong effect could be. FWIW, he now has a little girl with the woman he eventually married, but I think his wife who barely eats is responsible for that.

[atomic sagebrush]

I would wonder if a guy who could sleep in the same bed cuddling with a hot chick for 4 months and keep it platonic - that he might have lower T levels to start out with and also be more likely to father girls!

This is an older thread but I did want to mention that subsequent research has consistently supported this idea (single moms have more daughters) and that this research dates back to Charles Darwin himself!

[Tomgirl]

Well I was a single mom with my first 2, wasn't living with a man when I got pregnant with either one of them and I had 2 boys. Wasn't bedding frequently, both 1 shot wonders and low and behold boys. Number 3 was living with my husband but lots of stress and skinniest I've ever been working hours a day, 1 shot wonder and boy #3 it was. So not true in my case! Although I am just one to many but just goes to show not always true.

[maidentomother]

^^^Wow! Thanks for sharing that, it really does demonstrate how exceptions can occur no matter what. Are you fairly fertile/healthy?

AS, well, my friend DID have a huge crush on me - which I truly wish I could reciprocate as he is a wonderful person, but I just never felt that spark (I think bc he didn't smell sexy to me). From sharing a bed I can vouch that his equipment seem to work just fine, if you know what I mean. He was the one who wanted to cuddle and he wanted to despite how I felt, so I figured it was his choice. But he definitely has a masochistic streak, in more ways than that. I think he has always enjoyed pursuing women who aren't interested in him, as I observed him do so repeatedly.

He also had a vasectomy before I met him, and so maybe that swayed pink, as a reversal probably isn't ever as good as never having had a vasectomy in the first place. I'm sure he knows his T level, he probably checks it several times a month, and it might be on the low side...I will ask next time I talk to him! He likely has some brilliant insights on swaying. Oh, and he is bisexual, if that has any bearing on T levels or sex ratios?

[Tomgirl]

I am very fertile and healthy and come from a very fertile healthy family so getting pregnant has never been an issue. My mom had 4 girls and now she has 10 grandkids and only 3 are girls.

I'm sure there is some fascinating research out there on bisexuality and T levels and estrogen levels within a man.

[maidentomother]

Isn't it strange to feel like super-fertility is a bad thing? Really, it's not, but I wrestle with the whole concept...boy swayers have it so much easier, increasing fertility rather than trying to oh-so-carefully undermine it.

Why do you think your mom had girls?