The sins of the fathers are truly visited on the sons, at least among mice. When male mice exercise, their children are less anxious. Although the relevance to humans has yet to be proven, there are good reasons to think lifestyle effects are passed on through the father's line as well as the mother's.

Professor Anthony Hannan has authored many papers revealing how exercise and stimulation can reduce and delay the effects of conditions, such as Huntington's Disease and schizophrenia, where these were previously not thought relevant. He has now taken this back a generation, testing whether exercise in mice can change the health outcomes of their offspring.

Drs Annabel Short and Terence Pang from Hannan's team at the Florey Institute, Australia gave mice (which love to run) exercise wheels for four weeks, while a comparison group, were denied access to exercise opportunities. Each group then got to mate with females kept in low-exercise conditions. The offspring were given mental and behavioral tests at several ages and the results were published in Translational Psychiatry.

“Our most striking findings were that the male offspring of running mice were better at suppressing bad memories as juveniles, and had lower anxiety levels as adults than male offspring of sedentary fathers, Hannan said in a statement. “In contrast, female offspring of fit fathers showed no differences to the female offspring of sedentary fathers.”

Anxiety can be measured in mice by how much time they will spend in the dark when placed in a cages with lit and shaded areas. For rodents at least, it seems fear really does lead to the dark side.

Hannan pointed out to IFLScience that although maternal influence on offspring is well-established, it is hard to distinguish effects transmitted during pregnancy and breastfeeding from those that occur through changes to the genome. “With males you can do these clear-cut experiments," he said.

Although he told IFLScience there is a lot of work that needs to be done, Hannan said the team think they have made a start on understanding the mechanism. Small pieces of RNA produced by non-coding DNA “may set off a cascade where they can affect the regulation of many other genes”, altering sperm so that it affects the offspring.

Hannan told IFLScience similar mechanisms have been observed in animals as distant from rodents as nematode worms, suggesting what is seen in mice is likely to be applicable in men, even if it may not apply in exactly the same way.

Despite the vastly greater difficulties of researching such problems in humans, Hannan said his team are “talking to colleagues” about how to do long term cohort studies on humans. This will, he acknowledged, take “a lot of funding and a lot of time.”