There’s a chart at several web sites that claims to predict the sex of a woman’s child, based only on her age at conception and the month the baby was conceived.
It makes some strange claims, including that a 21 year old woman only has an 8% chance of conceiving a boy. I don’t see how the mother’s age and month of conception could have an impact on which sperm makes it to her egg first. I’m also dubious because IIRC, people’s ages are counted differently in China - you’re 1 when you’re born, not 0 - but the site doesn’t mention it, even though it’s vitally important for anyone in the Western world to know if they plan to use the chart.
Is there any evidence that a woman’s age and month of conception can influence the sex of her child?
Well, let’s say for the sake of argument that this chart was accurate for the time and place when it was originally produced. Perhaps seasonal variations in weather, diet, sunlight, or activities somehow affected whether X or Y sperm had the advantage - either causing the male to produce more of one type or more fit individuals of that type OR causing the female reproductive system to favor one type. And perhaps changes in the age of the mother caused age-related physical changes or changes in environment or activities that caused her reproductive system to somehow favor X or Y sperm. OR perhaps the age of the mother actually just correlated with the age of the father, and it was his age-related changes that did it.
So now that we’ve assumed that this is true for Chinese people in a certain region during a certain period in history, can we extend this to ourselves? Well, our weather is probably not the same as the weather in that region at that time, and even if it were, we use all sorts of spiffy climate control. We might be at a different latitude and so exposed to different amounts of seasonal sunlight. Even if we aren’t, we stay inside more and have more artificial light. We don’t have the same diet, either, and in most of the developed world, we don’t have all those seasonal variations in diet. The activities in our daily lives are not the same as those of people in China during that time period, and again probably don’t change as much with the seasons. Most of us probably don’t develop physically at exactly the same rate and in exactly the same way as the people for whom the chart was made. We probably don’t have the same age-related changes in activities and environment. Many of us are also not Chinese, and if the month of conception is such an important factor, it seems kind of silly to assume that ethnicity wouldn’t play any role.
Even if the chart was accurate when it was made, I can’t see how it could be accurate for, say, middle-class American office workers of European descent living in New Jersey. Some evidence would always be appreciated, though.
They didn’t use the Gregorian calendar in China 700 years ago. So I don’t see how a chart could have been produced accurately aligned to the modern months Jan-Dec. But then, astrology is usually pretty lackadaisical about these sort of things.
I’m also guessing that births to 45 year women were pretty rare at the time, so I can’t imagine how they verified their figures, or why they even bothered listing them.
So I think it’s safe to say that despite testiments of it’s ancient age, implications that the Beijing Institute of Science considers it of interest and unverified assurances of 93% accuracy, it’s total rubbish and so is everything said about it.
I think it’s bunk. It’s got a 50% chance of being right, or 1 out of 2. I’d buy a lottery ticket every week with those odds.
However I will point out anecdotally that almost every single teenage mother (like from age 15-18) I’ve ever known has had a boy. I don’t know if it’s just coincidence (probably) or maybe a teenage girl’s Ph balance is more likely to kill off little girl sperm than that of women who are older?