Could a fear of spiders, snakes (or even orcs) actually be an inherited defence mechanism laid down in a family’s genes by an ancestors’ frightening encounter with one of these terrifying beasts?

New research suggests that memories can be passed down through the generations as a result of chemical changes in DNA that allow offspring to inherit the experience of their ancestors. The research, carried out by Brian Dias and Kerry Ressler and published this week in the journal Nature Neuroscience may offer an insight into how phobias can develop.

Scientists have long assumed that memories and learned experiences built up during an individual’s lifetime must be passed on by teaching later generations or through social learning.

However, Dias and Ressler found that mice can pass on learned information about traumatic or stressful experiences to subsequent generations through their DNA.

They trained mice to fear the smell of cherry blossom using electric shocks before allowing them to breed. Their offspring also showed fearful responses to the odour of cherry blossom compared to a neutral odour, despite never having encountered either of these odours before.

The following generation of mice also showed the same behaviour and the effect continued even if the mice had been fathered through artificial insemination.

The researchers discovered structural changes in areas of the brain used to detect the odour in those mice that had been trained and also in their offspring. The DNA of these mice also carried chemical changes on the gene responsible for detecting the odour, suggesting that experiences had somehow been transferred from the brain into the genome, allowing them to be passed on to later generations.

Dias and Ressler now hope to explore whether similar effects can be seen in the genes of humans.