Menarche

Gertrude Himmelfarb once wrote dismissively of historians who believed that menarche was more important than monarchy. Ridiculous, she claimed.

She was wrong. Here we have Courtney Knapp with an extraordinary number calculated by Brown's excellent David Weil:

Menarche: Better health is causal factor behind the biological capability to become pregnant. Quick refresher course for those who slept through biology.... [H]ealthier girls have their first period at a younger age, and worldwide we have seen a decline in the age of menarche accompanying improved nutrition and sanitation. According to David Weil, in South Korea, the average age dropped from 16.8 to 12.7 between 1958 and 1998...

Comments

[Hedley Lamarr]

To solve the population problem you starve the girls?!

[Roger Albin]

Not the first or the last time Himmelfarb is off base by a huge margin. This is a generalizable phenomenon. In parts of rural 19th century Scandinavia, menarche was delayed until around 18. The social consequences are enormous.

[Ralph]

Another factor may be ubiquitous pollutants that possess estrogenic activity. The organochlorine pesticides, in particular, are bioaccumulative and tend to mimic estrogen. Most of the organochlorine pesticides have been phased out in the U.S. but they are persistent. For example, San Francisco Bay is listed under the Clean Water Act as impaired by organochlorine pesticides. Various other common chemicals currently is use also appear capable of affecting the human hormone system. The potential impacts on males are also unpleasant to contemplate.

Interesting discussion at: http://www.pbs.org/wgbh/pages/frontline/shows/nature/disrupt/vomsaal.html

[P.M.Lawrence]

"Accompanying"... It sounds like post hoc ergo propter hoc to me, what with everything else going on as well. The relevant point is the health/sanitation/nutrition issue.

Furthermore you can no more infer from this that menarche is more important than monarchy than you can infer that today's Iraq is an improvement on Saddam Hussein by looking at the latter's record in isolation. You need to assess both before you can come to a conclusion.

[shah8]

P.M. Lawrence...

actually, it really *is* more important than monarchy. Marriage age and number of children per women are determined by it, and social composition tends to determine which kings get to rule...

[LeftCoast]

I've read that the best predictor for the onset of menarche is body weight -- it occurs right around 100 pounds. Nutrition and sanitation haven't improved significantly in decades, childhood obesity has increased dramatically. It will undoubtedly have a large societal impact, but it is nothing to congratulate ourselves on.

[Edward Hugh]

"To solve the population problem you starve the girls?!"

Maybe your population focus is a little out of date. Our population problem in the OECD world is too few children. Now, interestingly enough, one of the big culprits in this is rising age at first childbirth, and the so called tempo effect, as identified by Bongaarts.

This is important since as the median childbirth age rises (and the US *is* different from the rest of the OECD in this sense, given that since the early 1970s immigration has meant that this age hasn't risen as much as elsewhere - don't worry, it will) as the median age rises fertility in the biological sense declines. This is the reason that all the surveys show women want on average two children, but reproductive difficulties as the age moves up prevent them having what they want.

All of which leads me to start asking myself, and if the drop in age at menarche has got something to do with this? I mean given that fertility is a biological time window, moving down the starting point may also move down the maximum, if this makes sense.

BTW Brad, this work also shows up some of the cruder applications of Malthusianism among economists. The positive checks have a biological element connected with female reproduction - or should these be nature's preventive checks. Whichever way you look at it there is a positive feedback/negative feedback process as better diet improves fertility (in the biological sense) and this may also then be associated with better economic prospects encouraging an increased rate of new home/family formation at a younger age.(Think UK pre industrial revolution from end 16th century). Also being more fertile, the gap between having children will be reduced. The whole thing kicks down again as the population grows beyond a critical point (I am talking about the pre-transition demographic regime). I doubt the menarche age is so important here, as most societies have pretty systematic rules governing marriage and family formation.

[a different chris]

As a parent I can say this is a mixed blessing at best.

[Richard Bellamy]

This is important since as the median childbirth age rises . . .

My sample size is fairly small (two children), but they were both exactly the same age as I was when I was born.

[Captain Button]

There was a "Scientific American" article some years ago that among other things, said that percentage of body fat was an important factor in age at menarche.

And back in college in 1977, the professor in my "The Biology of Sex" course said that the studies of age at menarche were mostly from areas with long cold winters, meaning that people spent much of the year eating cornmeal mush or the local equivalent. And that it was the lack of fresh food that made the difference.

He said that if you looked at warmer climates like Italy, the median age at menarche had always been 12.5 since the Roman Empire.

[Aaron]

Interesting that the BLOG should mention south Korea. Just yesterday The New York Times carried a story about how that Country's low birth rate was now considered a problem.

http://www.nytimes.com/2005/08/21/international/asia/21birthrate.html

Earlier onset of menarche occured simultaneously with lower birthrates.

The evidence, therefore, doesn't point toward birth rates and the attendant social relations being biologically determined. So it's not so clear to me that the timing of menarche is particularly important, except as news about public health of ambiguous import.

[dearieme]

When we lived in Australia, my wife observed that the men are about the same height as the British, but that the girls are taller. "How wonderful" she said "they've been so rich for so long that even the girls have been fed properly".

[Hedley Lamarr]

I said, "To solve the population problem you starve the girls?!"

And Edward Hugh replied, "Maybe your population focus is a little out of date. Our population problem in the OECD world is too few children."

Then you are not part of the population problem as it is known in Asia and elsewhere. Yours is the out of focus view; on yourselves.

[Edward Hugh]

"Earlier onset of menarche occured simultaneously with lower birthrates."

Thank you Aaron, that is precisely my point. The drop in fertility coincides with the age fertility bell curve moving to the left, while the age at childbirth distribution curve moves to the right.

"doesn't point toward birth rates and the attendant social relations being biologically determined"

I think the key word here would be 'determined'. They aren't biologically determined, social factors play a huge role, but biology does form one part of the picture, as many of the women who have postponed having children and are now having difficulty know to their cost.

"So it's not so clear to me that the timing of menarche is particularly important"

I hope it may now be a little clearer. If you want more info Harvard Anthropologist Peter Ellison's book On Fertile Ground is an interesting read:

http://www.amazon.com/exec/obidos/tg/detail/-/0674011120/qid=1124873928/sr=8-1/ref=pd_bbs_1/104-6953013-2715134?v=glance&s=books&n=507846

[Edward Hugh]

"Then you are not part of the population problem as it is known in Asia and elsewhere. Yours is the out of focus view; on yourselves."

I'm sorry Hedley, I think you aren't quite right here. Fertility is well below replacement in China, it is below replacement in some Indian states, and, incredibly it is now below replacement in Thailand. Whilst in the OECDthe ageing process can make us trim back, there is a real and present danger of many developing countries getting old before they get rich, and this could produce calamity.

As Aaaron notes, S Korea has begum to recognise its issue, and the rest of the 'tigers' likewise. Spore is even working on a population policy to raise the size of its population thru immigration.

So I am afraid you are definitely focused on what in general is 'yesterday's problem'. Of course there are a block of 'recalcitrants' - Niger would be a classic example - where the demographic transition still has to gain traction, but it will.

[Joerg Wenck]

Edward Hugh wrote:
"I mean given that fertility is a biological time window, moving down the starting point may also move down the maximum, if this makes sense."
No, it doesn´t. The biological time window expands in both directions. There have been several stories about 67-year-old women giving childbirth in different European countries - Italy and Bulgaria, I think. One case was stated to have involved hormone treatment - which presumably wasn´t widely available during most of human history.