https://www.theguard...-your-ancestors
This article claims that they trained mice to be aversive toward a food they normally like and that this training carried down two generations and the grandkids had the same aversion without learning it. I find it hard to believe.
The study made use of mice’s love of cherries. Typically, when a waft of sweet cherry scent reaches a mouse’s nose, a signal is sent to the nucleus accumbens, causing this pleasure zone to light up and motivate the mouse to scurry around in search of the treat. The scientists exposed a group of mice first to a cherry-like smell and then immediately to a mild electric shock. The mice quickly learned to freeze in anticipation every time they smelled cherries. They had pups, and their pups were left to lead happy lives without electric shocks, though with no access to cherries. The pups grew up and had offspring of their own.
At this point, the scientists took up the experiment again. Could the acquired association of a shock with the sweet smell possibly have been transmitted to the third generation? It had. The grandpups were highly fearful of and more sensitive to the smell of cherries. How had this happened? The team discovered that the DNA in the grandfather mouse’s sperm had changed shape. This in turn changed the way the neuronal circuit was laid down in his pups and their pups, rerouting some nerve cells from the nose away from the pleasure and reward circuits and connecting them to the amygdala, which is involved in fear. The gene for this olfactory receptor had been demethylated (chemically tagged), so that the circuits for detecting it were enhanced. Through a combination of these changes, the traumatic memories cascaded across generations to ensure the pups would acquire the hard-won wisdom that cherries might smell delicious, but were bad news.
The study’s authors wanted to rule out the possibility that learning by imitation might have played a part. So they took some of the mice’s descendants and fostered them out. They also took the sperm from the original traumatised mice, used IVF to conceive more pups and raised them away from their biological parents. The fostered pups and those that had been conceived via IVF still had increased sensitivity and different neural circuitry for the perception of that particular scent. Just to clinch things, pups of mice that had not experienced the traumatic linking of cherries with shocks did not show these changes even if they were fostered by parents who had.
