Your daily dose of science knowledge will once more be provided by Gregory Cochran, clearing up some misconceptions you may have heard about Epigenetics.

As I understand it, in some circles,  there is a burgeoning hope that practice in this generation will somehow improve performance in the next – based on a word they have heard but do not understand. That word is epigenetics.

Genes can certainly be modified in ways that persist.   For example, the cells in your skin produce more skin cells when they divide, rather than muscle cells or neurons.  Most of your cells have a copy of the entire human genome, but only certain elements are expressed in a particular type of cell, and that pattern persists  when that  kind of cell divides. We understand, to a degree, some of the chemical changes that cause these lasting changes in gene expression patterns.   One is methylation,  a method of suppressing gene activity.  It involves attaching a methyl group to a cytosine base. This methylation pattern is copied when somatic cells divide.

The question is whether A. such changes can persist into the next generation and B. if they do, is this some sort of adaptive process, rather than an occasional screwup?  We’re  interested in whether this happens in humans,  so we’ll only consider mammals.

It’s rare, but sometimes it happens.  It has only been found to happen at a few sites in the genome, and when it does happen,  only a fraction of the offspring are affected. Probably the best known example is the agouti yellow allele in mice.  Mice that carry this allele are fat, yellow, and prone to cancer and diabetes – some of them. Yellow mothers tend to have yellow babies,  while genetically identical brown mothers mostly have brown babies.  The agouti yellow allele is the product of a recent insertion in the genome, about 50 years ago.  For the overwhelming majority of genes, the epigenetic markers are reset in a new embryo, which means that epigenetic changes induced by the parent’s experiences disappear.  The embryo is back at square one.   This agouti yellow allele is screwed up – somehow the reset isn’t happening correctly.

In mice, the mammalian species in which most such investigations have been done,  the few other locations in the genome where anything like this happens are mainly retroposons and other repeated elements.

There is another way that you can get transmission across generations without genetic change.  Rats that are nurtured by stressed mothers are more likely to be stressed.  This isn’t transmitted perfectly, but it happens.  Presumably the uterine environment,  or maybe maternal behavior, is different in stressed mice in a way that stresses their offspring.   This reminds me of a science fiction story that abused this principle.  The  idea was that alligators (or maybe it was crocodiles) almost have a four-chambered heart, which is generally associated with higher metabolism and friskiness. Our protagonist operates on an alligator and soups up its heart: the now-more-vigorous animal has better blood circulation and lays healthier eggs that develop into babies that also have a working four-chambered heart. So ‘normal’ alligators were like stressed mice: fix the problem and you get to see what they’re really capable of. The problem was that the most interesting consequence was growing wings, flying around and eating people. Alligators turned out to be stunted dragons. Not so good.

Anyhow, what reason is there to believe that reading Gradshteyn and Ryzhik until your eyes bleed will plant the seeds of math to come in your descendants?  None. Oh, I can come up with a scenario, if you want: but it requires that civilization (in particular, the key part of civilization, heavy use of weird definite and indefinite integrals and vast reproductive rewards for those skilled in such things) has risen and fallen over and over again at fairly short (but irregular)  intervals, so that humans have faced this adaptive problem over and over and over again.  A little like the way in which generations of aphids do different things in the summer (parthenogenesis) than in the late fall (sexual reproduction) – although that probably depends on direct cues like length of day rather than epigenetic changes.  Something like Motie history, maybe. But  I don’t believe it.  Not even a little bit.

Nature hasn’t even figured out how to have Jewish boys be born circumcised yet.

So why are people talking about this? Why do people like Tyler Cowen invoke it to ward off evil facts?

Because they’re chuckleheads, what else?

I think we can be a bit more specific that that so lets take it as an exercise. Motivated cognition for starters.

If you want to learn why the Conan the Barbarian was generated by better priors than modern history books, what the blind idiot god may have in store for you or how to solve thick problems check out other articles from the blog shared under the tag: westhunter