Inherited Learned Behavior

There is what we inherit from our parents and there is what we learn from our own experience. The two are distinct, right? Well, actually no they are not separate. This was further demonstrated by a Princeton study (Danger avoidance can be genetically encoded for four generations, biologists say):

“Moore and her colleagues investigated whether C. elegans can convey this learned avoidance behavior to their progeny. They found that when mother worms learned to avoid pathogenic P. aeruginosa, their progeny also knew to avoid the bacteria. The natural attraction of offspring to Pseudomonas was overridden even though they had never previously encountered the pathogen. Remarkably, this inherited aversive behavior lasted for four generations, but in the fifth generation the worms were once again attracted to Pseudomonas.”

This is not an entirely new understanding. Earlier research has found similar results in other species. The study that always fascinates me had to do with rodents. The scent of cherry blossoms was emitted in their cage and immediately following that the bottom of the cage was electrified. Unsurprisingly, the rodents jumped around trying to avoid the pain. The rodents learned to begin jumping merely at the presence of the scent, whether or not any electric shock followed. The interesting part is that their rodent descendants, even though never shocked, would also jump when they smelled cherry blossoms. And this lasted for multiple generations. A very specific learned behavior was passed on.

Of course, this isn’t limited to worms and rodents. Humans are harder to study, partly because of our longer lives. But researchers have been able to observe multiple living generations to discover patterns. I’m not sure if this exactly fits into learned behavior, except in how the body learns to respond to the environment. It’s similar enough. This other research found that the children and grandchildren of famine survivors had higher rates of obesity that had nothing to do wasn’t caused by genetics or diet. It is what is called epigenetics, how the genes get set for expression. The same genes can be switched on or off in numerous ways in relation to other genes.

I find that fascinating. It also makes for much complication. Almost no research ever controls for multigenerational confounding factors. Epigenetics has been largely a black box, until quite recently. To be certain that a particular behavior was directly related to specific genetics in a population, you would have to be able to follow that population for many generations. To fully control for confounders, that would require a study that lasted more than a century. It might turn out that much of what we call ‘culture’ might more correctly be explained as population-wide epigenetics.

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As a side note, this would have immense significance to dietary and nutritional research. Many of the dietary changes that have happened in modern society are well within the range of epigenetic involvement. And the epigenetic effects likely would be cumulative.

We have an ongoing and uncontrolled experiment going on. No one knows the long-term consequences of the modern industrial diet of refined carbohydrates, added sugars, highly processed vegetable oils, food additives, farm chemicals, microplastic, etc. It’s a mass experiment and the subjects never chose to participate.

Definitely, we have reasons to be concerned. Francis M. Pottenger Jr. studied the dietary impact on feline health. He fed some cats a raw food diet, others a cooked food diet, and a third group with a diet mixed of raw and cooked. The cats on the cooked food diet became sickly in the first generation and were entirely infertile after a number of generations.

This is not exactly similar to the human diet of industrial foods. But it points to how results play out across generations. The worst effects aren’t necessarily seen in the immediate generation(s). It’s future generations that have to deal with what those before them caused, as true for epigenetics as it is for national debt and environmental destruction.