A child can be born with her mother’s eyes, her grandfather’s chin, her aunt’s nose, but what about her father’s work-induced propensity for stress?
Nurture certainly plays a role. Children are incredibly sensitive to the way their parents interact with other people. They may pick up social cues from their parents. Or they may be neglected or abused by their parents, as was discovered in a study of parents who had survived the Holocaust and suffered from post-traumatic stress disorder.
But plenty of studies show that anxiety is heritable, meaning that trauma felt by a parent can create a biological imprint in offspring. There’s an evolutionary argument for it—if mom experiences tough times, she’ll pass down that information via subtle genetic changes so that her child is better prepared for the outside world. Some of these changes happen in the womb if the mother goes through a stressful or traumatic event during pregnancy, but what about trauma that occurs before fertilization?
Here’s Virginia Hughes, reporting for National Geographic.
Traumatic experiences can actually work themselves into the germ line. When a male mouse becomes afraid of a specific smell, this fear is somehow transmitted into his sperm, the study found. His pups will also be afraid of the odor, and will pass that fear down to their pups.
Hughes learned of the study, which has yet to be published, in a talk at the Society for Neuroscience annual meeting. There, two Emory University researchers, Brian Dias, Ph.D., and Kerry Ressler, M.D., Ph.D., presented their findings. Dias and Ressler taught mice to be afraid of a certain fragrance, acetophenone, by shocking them every time they caught a whiff. Over time, the mice experienced small changes in their brains and even a rearrangement of the neurons in their noses to cope with this new stress in the environment.
Then, 10 days after the “startle” response was fully ingrained, the researchers allowed one group of the mice to mate while the another was artificially inseminated. In both groups, the offspring were startled by the smell, even without the shock training. The epigenetic changes appeared to occur before fertilization.
These results haven’t been without controversy. After Hughes’s article was published, other scientists weighed in on Twitter. She put together an excellent summary of the virtual conversation.
It’s still unclear how changes in the brain could lead to changes in the sperm.