46 Comments

Dave, it would be premature for you to make conclusions on it because you haven't read the literature. I have, and it is not premature for me to make such a conclusion.

There are many more pathways that involve nitric oxide. The Zn finger proteins are regulated by NO. That means that the pathways that regulate the Zn finger proteins produce an NO signal. That means the products that Zn finger transcription factors cause (or block) expression of, produce an NO signal to block (or cause) expression of more (or less) of that product.

Everything that Zn finger transcription factors couple to has to be coupled via NO signaling.

Expand full comment

Yes, thanks for pointing this out. I searched for references in the New England Journal of Medicine. Now I know what Zinc fingers are and see they are pervasive in protein transcription involving hematology and endocrinology.

So they could be a portal though many environmental factors have an effect. I still think it is premature to judge how this all works out in the real world for reasons I have given.It does make a nice pet theory.

Expand full comment

Robin isn't saying that divorce is the ONLY factor, just one of them. He clearly mentions increased obesity as a part of early menarche, and I've heard a bunch about lower childhood infectious disease being a contributor. The only chemicals involved as the antibiotics making sure kids don't die of infectious disease. :)

Expand full comment

But they are not unrelated. All of them are related in that they involve signaling with nitric oxide. The transfer of zinc from metallothionein (the main storage form of zinc) to zinc finger transcription factors (the largest class of transcription factors) occurs via oxidation of the Zn-thiol couple via NO species.

Regulation of the cytochrome P450 enzymes (the ones that synthesize cholesterol and steroids) is via nitric oxide. Regulation of ATP production is via nitric oxide, including mitochondria biogenesis, oxygen reduction at cytochrome c oxidase, mitochondrial inhibition, glycolysis via HIF-alpha, erythropoiesis via EPO, blood flow via shear mediated vasodilation.

All of the observed outcomes are known to occur via pathways that are known to be regulated by nitric oxide. There are not alternatives that don't involve nitric oxide.

Expand full comment

It always worries me when someone seizes upon a single factor as an underlying cause of a multiplicity of seemingly unrelated changes.The NO hypothesis seems to be imbedded in a blizzard of untested assumptions and the observed outcomes have numerous alternative explanations. So basically you are promoting a belief system. (So is everyone else.)

However it is true that there is vast ignorance concerning the normal bacterial inhabitants of the human body and the consequences of messing with them.

I was reviewing a bunch of obscure lung conditions the have been recently described and their is nothing but the vaguest idea what causes them. Same for skin and intestinal diseases.Yet vast amounts of data continue to be amassed.Humility is the best position here.

Expand full comment

Over the vast, vast, vast majority of evolutionary time, the average number of descendents the average woman had (survive and reproduce) was 2. If it was even 2.05, then in 1000 generations the number of humans would have reached numbers we know did not happen. (1.025)^1000 = 5e10.

Expand full comment

> I think that in industrialized countries the fraction of people who die > without children is way too small for evolution to be that fast.

I think in the US it's around 20 percent of women and a higher percentage of men. And the number of children per person who had children is also highly variable.

I called it a guess for a reason, but I don't think "evolution can't happen that fast" is the reason it's implausible. The effect, preference for less masculine guys, is studied, but I'm not sure the magnitude is sufficient to drive change this fast. Also, I don't see that it explains the racial and socioeconomic differential effects unless the pill has been differentially used by those communities. It might have been, but I don't know that.

Expand full comment

> Why are people so much more willing to use strange chemicals to explain earlier puberty that other trends like increasing IQ, lifespan, and height? Is it because chemicals are bad, and therefore can only explain bad things?

Generally, I'd expect a difference between traits caused by exposure to new chemicals vs. traits caused by adaptation to new social environments: the former should only rarely be adaptive, the latter often so. (I don't know whether or not earlier puberty is adaptive.)

Expand full comment

I think that in industrialized countries the fraction of people who die without children is way too small for evolution to be that fast.

Expand full comment

All stress effects are mediated through a lowering of nitric oxide levels. Low NO is physiology's signal of "stress", and yes, it does accelerate maturation, but at a cost of degenerative disorders.

What is very worrying to me (knowing what I know) is that stress also causes epigenetic programming of DNA in gametes. If you raise the stress level enough, people may program stress responses in their children's DNA that make reproduction impossible. That is what John Calhoun found in mice.

http://www.ncbi.nlm.nih.gov...

Give a breeding population of mice everything that they need, food, water, air and they soon go extinct. This is just due to psychosocial stress, no toxins are needed.

Expand full comment

I'm going to go with stress, and posit significant childhood stress pushes us all out of childhood faster. From an evolutionary angle, it makes sense for a child growing up in a hostile (stressful) environment to mature earlier in order to reproduce or possibly to escape or help to improve the environment.

Citing chemical causes is easy, can't be disproved, and I would be surprised if doctors haven't found chemicals (hormones, I'm guessing) that will cause early onset puberty.

I'm just going to say that stress can be chemically, physically, or socially induced. Everyone wins!

Expand full comment

Being a single mother is *also* indicative of poverty - and that surely brings us back to a much simpler and more general r/K-selection model based on percieved resource availability.

Expand full comment

You may be on to something. The corporate rulers are not interested in slave workers. Late maturing nerds are good workers at operating the few high tech machines that are needed. Their own children can take the high paying responsibility jobs upon graduation from Ivy League grad schools.

But what the ruling class needs is to keep the operation profitable is hyper-mature little girls to buy I- Phones and other consumer junk.

People in government benefit too and are undoubtedly involved,making big bucks off of proliferating family dysfunction as teachers,guidance counselors and prison guards. Heh heh!!The chemicals themselves can even be imbedded in the plastic they use to make the products!!

Expand full comment

The racial effect is much more likley to be due to biological differences between human groups considering such effects have been shown to be independent of socio-economic factors.

Differences in onset of certain diseases, signs of ageing, age of first menarch, how common twins are clearly established between some ethnic and racial groups.

An extreme example of this may be the Pygmy's

"I found cases of women 28 years old who said they no longer experienced menstruation. Very few births were occurring to women more than 30 years of age," he said

But naturally such explanations aren't popular even when the effects are as dramatic as they are.

Migliano's theory will no doubt be controversial, particularly among creationists and proponents of intelligent design, because it proposes that pygmies are proof of how our species, Homo sapiens, continues to evolve.

Expand full comment

There are a lot of "IQ" zealots out there however:

* There are problems with defining intelligence in ways both subjective and objective. Facts, reality, and intelligence are all both subjectively and objectively disputed.

* A ruling class would try to control the "intelligence" test to its benefit.

* The "Delta's" version of the IQ / "intelligence" test might be totally misleading for "certain" conclusions about what is intelligence.

* We're talking about sheep who engineer mutton. Don't go off of the mainstream consensus.

Therefore:-->You're going off of bad sources.

Expand full comment

My guess is that it's a generations-long effect of better nutrition (and maybe other aspects of general health). It's known that non-genetic changes that affect gene expression can be inherited. It makes evolutionary sense that age of sexual maturity should be lower if there is a good indication that times will be good, and hence rapid reproduction will be possible. But it doesn't seem very safe to base this on food supply (and other good things) having been good for the few years that the person has been alive to personally experience it. Better to base it on a longer time period going back to that person's parents and grandparents.

Of course, like most commenters, I'm putting forward this theory without citing any actual evidence...

Expand full comment