Now comes a potentially revolutionary new mice smell-aversion study, published Dec. 1 in Nature Neuroscience, to explain the link between ancestral trauma and mental health risk in downstream generations for the entire human race.
The research suggests that fearful memories in grandfathers and fathers can be passed to sons and grandsons, at least in mice.
It means that heritable neuropsychiatric disorders like schizophrenia may best be viewed through a multigenerational lens, much like the one that took me to Ireland to investigate a bulge in rates of insanty in our ancestral homeland that had mirrored, macrocosmically, what was going on in our family, microcosmically, back here in Boston.
In a just-published study led by Emory University’s Dr. Brian Dias, mice trained by foot shocks to fear a smell similar to cherry blossoms had two generations of offspring that feared the same odor, even though they’d never encountered it or met their ancestors.
It’ll take a lot more work for the guys in the white lab coats to get a firm fix on how imprinted memories of ancestral trauma might raise mental illness risks. But if the results can be replicated, and the genetic mechanism better understood, it would shed more light on the schizophrenia that has darkened our family tree for multiple generations (the motivation for my quest book, Stalking Irish Madness, a free digital version of which is available upon request at firstname.lastname@example.org).
Since environmental influences are hard to measure, the researchers looked at brain circuits that process smell. “We thought it would give us a molecular foothold into how trans-generational inheritance might occur,” Dias said.
When they next went looking inside the DNA of the sperm of the frightened mice, they saw that the bits responsible for sensitivity to the cherry blossom scent had been altered too.
The paper doesn’t describe the behavioral changes in the mice in vivid detail. It says that the offspring mice were “extremely sensitive” to cherry blossoms and would shun the scent.
The notion that mice inherit specific smell memories from their fathers and grandfathers seems, initially, like a potential game changer.
Some geneticists have deemed the Emory study revolutionary while others are still scratching their heads at the idea that a mere mouse that has never met his father and grandfather—or smelled the fearful odors they had to smell—would be born with the same bad memories.
Others are flocking to the study because what’s known as “Lamarckian” inheritance—a largely discredited theory, or so we thought, that claimed that learned behaviors could be passed down to subsequent generations—may be defunct no more.
It’s always fascinating when science defies itself. It’s well established that physical traits are passed down, but Mendelian genetics long ago supplanted the idea that acquired trait could be inherited.
Still, interest in Lamarckism has never died as studies in the field of epigenetics have raised the possibility of inheritance of behavioral traits acquired by the previous generation.
To use my own family history as a case study, we’ve long known that in-vitro malnourishment during famine mutates genes that doubles risk of schizophrenia.
We’ve also known that older fathers—a common feature of a century of continuous famine economy in Ireland—mutates genes in sperm cells that double risk of schizophrenia in offspring too.
Nothing too complex there. But if memory itself is heritable, then the whole field of public health may need a rewrite.
What of the smell of rotting potatoes? Or the whiff of English gunpowder? Do memories of ravages live on?
What of the memories of the bayonet of the Black and Tans, the Scottish thugs employed by the Crown to crush Irish rebels? Do war memories roll like marbles into subsequent generations?
Did the inferno of hatred that burned in Ireland transmit those memories?
Is our own mental health impervious to our father’s wars?
Or do these cruelties imprint genetic memories?
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Last reviewed: 6 Dec 2013