Memories may be passed down through generations in DNA in a process that may be the underlying cause of phobias. Memories can be passed down to later generations through genetic switches that allow offspring to inherit the experience of their ancestors, according to new research that may explain how phobias can develop.
Scientists have long assumed that memories and learned experiences built up during a lifetime must be passed on by teaching later generations or through personal experience. However, new research has shown that it is possible for some information to be inherited biologically through chemical changes that occur in DNA. Researchers at the Emory University School of Medicine, in Atlanta, found that mice can pass on learned information about traumatic or stressful experiences – in this case a fear of the smell of cherry blossom – to subsequent generations. The results may help to explain why people suffer from seemingly irrational phobias – it may be based on the inherited experiences of their ancestors.
So a fear of spiders may in fact be an inherited defense mechanism laid down in a families genes by an ancestors’ frightening encounter with an arachnid. In the study, which is published in the journal of Nature Neuroscience, the researchers trained mice to fear the smell of cherry blossom using electric shocks before allowing them to breed.
The offspring produced showed fearful responses to the odor of cherry blossom compared to a neutral odor, despite never having encountered them before. The following generation also showed the same behavior. This effect continued even if the mice had been fathered through artificial insemination. The researchers found the brains of the trained mice and their offspring showed structural changes in areas used to detect the odor. The DNA of the animals also carried chemical changes, known as epigenetic methylation, on the gene responsible for detecting the odor.
This suggests that experiences are somehow transferred from the brain into the genome, allowing them to be passed on to later generations. The researchers now hope to carry out further work to understand how the information comes to be stored on the DNA in the first place. They also want to explore whether similar effects can be seen in the genes of humans.