I have heard that our average height, as compared to our forebearers of, say, 1,000 years ago, and our earlier onset of menses (obviously I use the pronoun here in its indefinite sense) are the result of better nutrition.
Is that it? If I hop in Professor Bricker’s New and Improved Time Machine and zip back to the Battle of Hastings and kidnap a newborn, bringing him back here to enjoy the benefits of modern dining, will he grow as tall as the average man today? If I kidnap a baby girl, will she get her period as young as her classmates? Or, assuming it’s a matter of pre-natal care, let’s give my kidnapees a generation and look at their children – let’s assume they grow up here present-day, find each other compelling and decide to get hitched at adulthood and have a child themselves, fully the beneficiary of good eats and good vitamins from conception onwards, is THAT the point where our better nutrition results kick in? Or is there another factor to the issue?
While I cannot say much about height, I can tell you with reasonable certainty that the earlier and earlier onset of menstruation in Western (ie, American/European) girls is due to increased nutrition and decreased activity levels. US/European girls, in general, have high-quality nutrition (and higher levels of body fat) and an increasingly sedentary lifestyle. This lowers the age of menarche, basically because the girl’s body realizes that it is (nutritionally) capable of pregnancy and childbirth. Girls in Non-Western cultures and regions where diet is compromised still average around 16+ at menarche, while US/European girls average 12.6 (according to Wikipedia). Girls with athletic lifestyles or eating disorders (who have less body fat) usually begin menstruating later than the average.
My gf’s extended family moved from Vietnam when she was young and you can see a fairly distinct size difference between the generations that were born in Vietnam and those that were born here. I’ve noticed a similar effect at her Temple, which serves several hundred recent Vietnamese immigrants, the younger generation is considerably taller then their parents and grandparents, who by and large were born in Vietnam during the various wars there and thus were presumably not terribly well nourished.
Not sure where you heard that, but it’s demonstrably not true. Huge numbers of people had no problems with nutrirtion in the first half of the 20th century, yet heights and age of puberty have been going up and down respectively in the last 50 years.
If we accept the the effect is primarily instrinsicly physiological, which is debtable, the explanation is not one of improved nutrition alone, but an improvement in helath and standard of living generally. Children today not only eat better, they also suffer from far less disease and less chronic injury, they sleep longer, they physically work harder and numerous other factors that are all believed to be as significant or more significant than nutrition.
And as I said, the idea that the phenomenon is entirely or primarily intrinsically physiological is still open to debate. We know for example that children of signal mothers reach menarche some 6-12 months earlier than children from intact families. While there are some confounding effects due to the corrleations between single motherhood and race and obesity when we control for those factors to the extent possible the effect still remains. That suggests that the phenomenon of earlier puberty is at least partially due to social or extrinsic physiological factors, whether psychosomatic or pheromonal.
There are also a range of other factors that would need to be explained if we wish to invoke a purely physiological basis for the observations, such as why the effect varies geographically and even between religious groups. Some of that has been attributed to factors such as exposure to synthetic sex hormones such as phytooestrogens and pesticides, some has been attributed to exposure to sunlight, some to the amount of sleep and to a plethora of other factors.
Summary at this stage is that we can be fairly confident that the increas in average height seen from 1000 to 1900 is due to nutrition. Changes in height and age of menarche see in the 20th century are much harder to attribute to any cause although certainly improved helath (not just nutrition) play an imprtant role.
Nope, no matter what the cause. His mother will have been small, and children born to smaller mothers are smaller in adulthood even when all other factors are controlled for. If you transplant a thoroughbred embryo into a pony the foal will (probbaly) be born perfectly healthy but it wil never attain the height of its biological parents.
So we’d expect your child to be taller than his parents, but not as tall as the average modern man.
Probably not. See above.
For height we would assume that you’d be getting pretty close to modern height at this point. For other factors, nope.
Age of menarche has plummeted just within the last century. On average, each generation of women got it a year earlier than their mothers until about 20 years ago. I don’t think you can make a similar statement about height.