For the first time, scientists have discovered a mechanism in humans that could explain how your lifestyle choices may impact your children and grandchildren’s genes.

Mounting evidence suggests that environmental factors such as smoking, diet and stress, can leave their mark on the genes of your children and grandchildren. For example, girls born to Dutch women who were pregnant during a long famine at the end of the second world war had twice the usual risk of developing schizophrenia. Likewise, male mice that experience early life stress give rise to two generations of offspring that have increased depression and anxiety, despite being raised in a caring environment.

This has puzzled many geneticists, as genetic information contained in sperm and eggs is not supposed to be affected by the environment, a principle called the August Weismann barrier.

But we also know the activity of our own genes can be changed by our environment, through epigenetic mechanisms .