Your ancestors' lousy childhoods or excellent adventures might change your personality, bequeathing anxiety or resilience by altering the epigenetic expressions of genes in the brain.
By Dan Hurley|Tuesday, April 23, 2013
[This article originally appeared in print as "Trait vs. Fate"]
Darwin and Freud walk into a bar. Two alcoholic mice — a
mother and her son — sit on two bar stools, lapping gin from two
thimbles.
The mother mouse looks up and says, “Hey, geniuses, tell me how my son got into this sorry state.”
“Bad inheritance,” says Darwin.
“Bad mothering,” says Freud.
For over a hundred years, those two views — nature or
nurture, biology or psychology — offered opposing explanations for how
behaviors develop and persist, not only within a single individual but
across generations.
And then, in 1992, two young scientists following in
Freud’s and Darwin’s footsteps actually did walk into a bar. And by the
time they walked out, a few beers later, they had begun to forge a
revolutionary new synthesis of how life experiences could directly
affect your genes — and not only your own life experiences, but those of
your mother’s, grandmother’s and beyond.
The bar was in Madrid, where the Cajal
Institute, Spain’s oldest academic center for the study of neurobiology,
was holding an international meeting. Moshe Szyf, a molecular biologist
and geneticist at McGill University in Montreal, had never studied
psychology or neurology, but he had been talked into attending by a
colleague who thought his work might have some application. Likewise,
Michael Meaney, a McGill neurobiologist, had been talked into attending
by the same colleague, who thought Meaney’s research into animal models
of maternal neglect might benefit from Szyf’s perspective.
“I
can still visualize the place — it was a corner bar that specialized in
pizza,” Meaney says. “Moshe, being kosher, was interested in kosher
calories. Beer is kosher. Moshe can drink beer anywhere. And I’m Irish.
So it was perfect.”
The two engaged in animated conversation about a hot new
line of research in genetics. Since the 1970s, researchers had known
that the tightly wound spools of DNA inside each cell’s nucleus require
something extra to tell them exactly which genes to transcribe, whether
for a heart cell, a liver cell or a brain cell.
One such extra element is the methyl group, a common
structural component of organic molecules. The methyl group works like a
placeholder in a cookbook, attaching to the DNA within each cell to
select only those recipes — er, genes — necessary for that particular
cell’s proteins. Because methyl groups are attached to the genes,
residing beside but separate from the double-helix DNA code, the field
was dubbed epigenetics, from the prefix epi (Greek for over, outer, above).
Originally these epigenetic changes were believed to occur
only during fetal development. But pioneering studies showed that
molecular bric-a-brac could be added to DNA in adulthood, setting off a
cascade of cellular changes resulting in cancer. Sometimes methyl groups
attached to DNA thanks to changes in diet; other times, exposure to
certain chemicals appeared to be the cause. Szyf showed that correcting
epigenetic changes with drugs could cure certain cancers in animals.
Geneticists were especially surprised to find that
epigenetic change could be passed down from parent to child, one
generation after the next. A study from Randy Jirtle of Duke University
showed that when female mice are fed a diet rich in methyl groups, the
fur pigment of subsequent offspring is permanently altered. Without any
change to DNA at all, methyl groups could be added or subtracted, and
the changes were inherited much like a mutation in a gene.
Now,
at the bar in Madrid, Szyf and Meaney considered a hypothesis as
improbable as it was profound: If diet and chemicals can cause
epigenetic changes, could certain experiences — child neglect, drug
abuse or other severe stresses — also set off epigenetic changes to the
DNA inside the neurons of a person’s brain? That question turned out to
be the basis of a new field, behavioral epigenetics, now so vibrant it
has spawned dozens of studies and suggested profound new treatments to
heal the brain.
According to the new insights of behavioral epigenetics,
traumatic experiences in our past, or in our recent ancestors’ past,
leave molecular scars adhering to our DNA. Jews whose great-grandparents
were chased from their Russian shtetls; Chinese whose grandparents
lived through the ravages of the Cultural Revolution; young immigrants
from Africa whose parents survived massacres; adults of every ethnicity
who grew up with alcoholic or abusive parents — all carry with them more
than just memories.
Like silt deposited on the cogs of a finely tuned machine
after the seawater of a tsunami recedes, our experiences, and those of
our forebears, are never gone, even if they have been forgotten. They
become a part of us, a molecular residue holding fast to our genetic
scaffolding. The DNA remains the same, but psychological and behavioral
tendencies are inherited. You might have inherited not just your
grandmother’s knobby knees, but also her predisposition toward
depression caused by the neglect she suffered as a newborn.
Or not. If your grandmother was adopted by nurturing
parents, you might be enjoying the boost she received thanks to their
love and support. The mechanisms of behavioral epigenetics underlie not
only deficits and weaknesses but strengths and resiliencies, too. And
for those unlucky enough to descend from miserable or withholding
grandparents, emerging drug treatments could reset not just mood, but
the epigenetic changes themselves. Like grandmother’s vintage dress, you
could wear it or have it altered. The genome has long been known as the
blueprint of life, but the epigenome is life’s Etch A Sketch: Shake it
hard enough, and you can wipe clean the family curse.
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2 comments:
Fascinating. I remember Campbell in the first volume of his Masks of God series talked about 'innate release mechanisms'....i.e., an in-born behavioral given. A baby chick removed from its mother at birth, will automatically run for cover if a black silhouette of a hawk hovers overhead, etc...Campbell also mentioned the idea that some behaviors are genetic and have their own 'time-release' schedule, so to speak. While born with a behavioral tendency, it doesn't act out until a particular time, etc...makes me think of certain psychotic disorders that don't show up til young adulthood...just thinking aloud here...thanks for the stimulation!
And on top of all that, cells divide and are replaced, in some cases, as much as once a week. Which leads me to believe they might actually be talking to each other! Thank goodness they are not like people and are for the most part, very cooperative in nature!
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