Inheritance of Fear

Do ancestors pass on their phobias and fears to their offspring? It is probable

Is it possible that some of our phobias might have been biologically inherited? According to a new study published in Nature Neuroscience, it is likely that individuals inherit experiences and fears of their ancestors through chemical changes that occur in their DNA.

The study, conducted by researchers from Emory School of Medicine in Atlanta, US, suggests that fear can be transmitted from a father, through his sperm, to his offspring. In the study, mice were trained in a laboratory to fear the smell of acetophenone, a chemical that smells like cherry blossom. This was done by giving small electric shocks to the male mice, while releasing the scent of the chemical in a chamber, thereby making the mice associate the scent with pain.

In later experiments, the researchers found that the offspring of the mice who had come to fear the smell of acetophenone, despite never having encountered the chemical in their lives, exhibited increased sensitivity when introduced to its smell. The offspring started shuddering markedly in the presence of the smell compared with the descendants of mice that had been conditioned to be afraid of a different smell or had undergone no such conditioning.

The third generation of the original mice who had been trained to fear the smell of acetophenone, had also inherited the fear of the chemical. Mice conceived through in vitro fertilisation with the sperm of males sensitised to acetophenone also showed the same fear. Other similar experiments with female mice showed that this fear can be transmitted through mothers as well.

It was also found that changes had also occurred in brain structures. The mice sensitised to acetophenone, as well as their descendants, had more neurons that produce a receptor protein known to detect the odour, compared with mice that had not been conditioned.

The study offers evidence that the environment can affect an individual’s genetics, which can in turn be passed on. One of the researchers, Dr Brian Dias, says, “This might be one mechanism [by which] descendants show imprints of their ancestor… There is absolutely no doubt that what happens to the sperm and egg will affect subsequent generations.”

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