It’s the Environment, Stupid

A recent article in Science reviews work in behavioral epigenetics. Epigenetics is the science of how genes are turned off and on. A good deal of attention has been paid to epigenetics in explaining the risks of chronic illness based on the mischief done by environmental stressors such as toxic exposures, malnutrition, and early childhood and prenatal trauma. Behavioral epigenetics hopes to explain these connections.

This work began about 15 years ago with the study of how the nurturing behavior of mother rat affected their pups and how well those pups, once grown to adulthood, were able to cope with stressful situations: pups that were nurtured well coped much better than pups who were not. The research also revealed that females who were not well nurtured turned out to be mothers who were not good nurturers themselves. In both cases, epigenetic processes were associated with these outcomes.

Currently, research is looking into a wide range of behavioral effects, including addiction and health disparities associated with injustice. According to this line of research, there are three epigenetic mechanisms: methylation of DNA that suppresses gene expression, histone methylation that also suppresses gene expression, and histone acetylation that promotes gene expression. You’ll recall that “gene expression” just means the work that a stretch of DNA does. “Methylation” means attachment to a specific part of the DNA molecule by a methyl group, which consists of a carbon atom and three hydrogen atoms. Methylation also means methyl group attachment to a histone, which is a protein that packages DNA and controls whether it’s open for business or not. “Acetylation” means attachment to a histone protein by an acetyl group, which consists of a methyl group with a carbon atom and oxygen atom tagged on. Methylation of DNA and a histone prevents a gene from doing its work while acetylation of a histone promotes a gene doing its work.

For example, the rats that were not well nurtured had more methylation of DNA in regions responsible for creating stress hormone receptors. With fewer receptors, hormones created during a stressful experience remained in circulation. As a consequence, the rats reacted more strongly. And the epigenetic effect was passed on from mother to daughter, so that females who weren’t well-nurture did not do well in nurturing their own pups.

Where is this research headed?

Drugs. Biotech and drug companies are very interested, just as they were in the human genome project. The objective is to develop chemicals that can block or promote methylation and acetylation and, consequently, reverse the effects of early life trauma, social injustice, malnutrition, and addiction, to name a few.

What happened to nutrients that block and promote epigenetic changes? After all, there are sophisticated biochemical pathways of considerable complexity that respond epigenetically to environmental exposures. There are also complex biochemical pathways from the epigenetic effect of methylation and acetylation to an individual’s actual ability to cope with stressful situations.

And what happened to changing the environmental exposures that lead to an epigenetic response? Isn’t the obvious answer to prevent early life trauma, social injustice, malnutrition, and the sources of addiction? Isn’t the obvious answer to use our social intelligence in conjunction with our already well-developed biochemical pathways to avert these outcomes? Doesn’t this make more sense than relying on the demonstrably false assumption that drug interventions are effective in all cases without side effects? Doesn’t it make more sense to assume that social and nutrient support are a more effective method because they use our already existing and quite robust biochemistry?

But that’s not how science is done. And it’s not how science is reported to us.

Twenty years ago anthropologist Louis Liebenberg wrote a nice little book titled The Art of Tracking: The Origin of Science. In it he argued that hunter-gatherers used the same skills and processes as scientists do today. What differs between them is acculturation and context.

I think this is inspired. But I think it’s more a prescription about how science ought to be done than a description of how science is actually done.

Too often science consists of hypothesis testing done piecemeal and out of context. It’s a mode of thought that’s developed over the last 500 years—about 20 generations. Hunter-gatherer tracking, what our biology adapted to over tens of thousands of generations, is hypothesis testing from the perspective of the ecological whole and done very much in the context of a way of life.

The epigenetics of behavior is a very small part of the picture we need to understand in order alleviate the suffering that has drawn researchers’ interest. It’s like discovering how bullets kill people. That’s good to know, but it doesn’t prevent anyone from getting shot.

The weakness here is not in these researchers’ work or their motivation in pursuing it. The weakness is the context we as a culture have created for them. What we need to demand is science that alleviates suffering in the context of our natural history.