This is an important item that properly updates us on the present
reality of scientific thought of the topic of inheritance. It has
been clear to me for a number of years that parents change the
genetic outcome of their offspring somehow other that natural
selection which has been the prevailing dogma. I speculated as to
means and all that.
At the same time, the field itself was coming to the same conclusion
and the name of Lamarck is even mentioned here quite honorably.
This now shows us experiments that confirm the hypothesis and the
necessary pathways are now been winkled out. It turns out that way
more information is transmitted on conception than the core DNA. It
is an astonishing idea and powerfully reinforces the core role of
fathers generally that has been challenged in the past two
generations.
It is worth a slow reflective reading and it is also sobering. Our
society has conducted an experiment over the past two generations
that needs to fully rethought and plausibly reformed.
Why Fathers Really
Matter
Paul Blow
By JUDITH
SHULEVITZ
MOTHERHOOD begins as a
tempestuously physical experience but quickly becomes a political
one. Once a woman’s pregnancy goes public, the storm
moves outside. Don’t pile on the pounds! Your child will be obese.
Don’t eat too little, or your baby will be born too small. For
heaven’s sake, don’t drink alcohol. Oh, please: you can sip some
wine now and again. And no matter how many contradictory things the
experts say, don’t panic. Stress hormones wreak havoc on a baby’s
budding nervous system.
All this advice rains
down on expectant mothers for the obvious reason that mothers carry
babies and create the environments in which they grow. What if it
turned out, though, that expectant fathers molded babies, too, and
not just by way of genes?
Biology is making it
clearer by the day that a man’s health and well-being have a
measurable impact on his future children’s health and happiness.
This is not because a strong, resilient man has a greater likelihood
of being a fabulous dad — or not only for that reason — or
because he’s probably got good genes. Whether a man’s genes are
good or bad (and whatever “good” and “bad” mean in this
context), his children’s bodies and minds will reflect lifestyle
choices he has made over the years, even if he made those choices
long before he ever imagined himself strapping on a Baby Bjorn.
Doctors have been
telling men for years that smoking, drinking and recreational drugs
can lower the quality of their sperm. What doctors should probably
add is that the health of unborn children can be affected by what and
how much men eat; the toxins they absorb; the traumas they endure;
their poverty or powerlessness; and their age at the time of
conception. In other words, what a man needs to know is that his life
experience leaves biological traces on his children. Even more
astonishingly, those children may pass those traces along to their
children.
Before I began reading
up on fathers and their influence on future generations, I had a
high-school-biology-level understanding of how a man passes his
traits on to his child. His sperm and the mother’s egg smash into
each other, his sperm tosses in one set of chromosomes, the egg
tosses in another, and a child’s genetic future is set for life.
Physical features: check. Character: check. Cognitive style: check.
But the pathways of inheritance, I’ve learned, are subtler and more
varied than that. Genes matter, and culture matters, and how fathers
behave matters, too.
Lately scientists have
become obsessed with a means of inheritance that isn’t genetic but
isn’t nongenetic either. It’s epigenetic. “Epi,” in
Greek, means “above” or “beyond.” Think of epigenetics as the
way our bodies modify their genetic makeup. Epigenetics describes how
genes are turned on or off, in part through compounds that hitch on
top of DNA — or else jump off it — determining whether it makes
the proteins that tell our bodies what to do.
In the past decade or
so, the study of epigenetics has become so popular it’s practically
a fad. Psychologists and sociologists particularly like it because
gene expression or suppression is to some degree dictated by the
environment and plays at least as large a role as genes do in the
development of a person’s temperament, body shape and
predisposition to disease. I’ve become obsessed with epigenetics
because it strikes me as both game-changing and terrifying. Our genes
can be switched on or off by three environmental factors, among other
things: what we ingest (food, drink, air, toxins); what we experience
(stress, trauma); and how long we live.
Epigenetics means that
our physical and mental tendencies were not set in stone during the
Pleistocene age, as evolutionary psychology sometimes seems
to claim. Rather, they’re shaped by the life we lead and the world
we live in right now. Epigenetics proves that we are the products of
history, public as well as private, in parts of us that are so
intimately ours that few people ever imagined that history could
reach them. (One person who did imagine it is the French 18th-century
naturalist Jean-Baptiste Lamarck, who believed that acquired traits
could be inherited. Twentieth-century Darwinian genetics dismissed
Lamarckism as laughable, but because of epigenetics, Lamarckism
is staging a comeback.)
The best-known example
of the power of nutrition to affect the genes of fathers
and sons comes from a corner of northern Sweden called Overkalix.
Until the 20th century, Overkalix was cut off from the rest of the
world, unreachable by road, train or even, in wintertime, boat,
because the frozen Baltic Sea could not be crossed. Thus, when there
were bad harvests in Overkalix, the children starved, and when there
were good harvests, they stuffed themselves.
More than a decade
ago, three Swedish researchers dug up records from Overkalix going
back to 1799 in order to correlate its children’s health data with
records of regional harvests and other documents showing when food
was and wasn’t available. What the researchers learned was
extremely odd. They found that when boys ate badly during the years
right before puberty, between the ages of 9 and 12, their sons,
as adults, had lower than normal rates of heart disease. When boys
ate all too well during that period, their grandsons had higher rates
of diabetes.
When the
study appeared in 2002, a British geneticist published an
essay speculating that how much a boy ate in prepuberty could
permanently reprogram the epigenetic switches that would govern the
manufacture of sperm a few years later. And then, in a process so
intricate that no one agrees yet how it happens but probably has
something to do with the germline (the reproductive cells that are
handed down to children, and to children’s children), those
reprogrammed switches are transferred to his sons and his sons’
sons.
A decade later, animal
studies confirm that a male mammal’s nutritional past has a
surprisingly strong effect on his offspring. Male rats that are
starved before they’re mated produce offspring with less blood
sugar and altered levels of corticosterone (which protects against
stress) and insulin-like growth factor 1 (which helps babies
develop).
Southeast Asian men
who chew betel nuts, a snack that contains a chemical affecting
metabolic functioning, are more likely to have children with weight
problems and heart disease. Animal studies have shown that the
effects of betel nut consumption by a male may extend to his
grandchildren.
Environmental toxins
leave even more florid traces on grandchildren and
great-grandchildren. Vinclozin, a fungicide that used to be sprayed
all over America (it’s less common now), is what’s known as an
endocrine disrupter; it blocks the production oftestosterone. Male
rats whose mothers receive a fat dose of vinclozin late in their
pregnancy are highly likely to be born with defective testicles and
reduced fertility. These problems seem to reappear in up to four
generations of male rats after the mother is poisoned.
THAT food and poison
change us is not all that surprising, even if it is surprising how
far down the change goes. What is unexpected are the psychological
dimensions of epigenetics. To learn more about these, I visited the
Mount Sinai Medical Center laboratory of Dr. Eric Nestler, a
psychiatrist who did a discomfiting study on male mice and what he
calls “social defeat.” His researchers put small normal field
mice in cages with big, nasty retired breeders, and let the big mice
attack the smaller mice for about five minutes a day. If a mean mouse
and a little mouse were pried apart by means of a screen, the
torturer would claw at the screen, trying to get at his victim. All
this subjected the field mouse to “a horrendous level of stress,”
Dr. Nestler told me. This process was repeated for 10 days, with a
different tormentor placed in each cage every day. By the time the
torture stopped, about two-thirds of the field mice exhibited
permanent and quantifiable symptoms of the mouse equivalents
of depression, anxiety and post-traumatic stress disorder.
The researchers then bred these unhappy mice with normal females.
When their pups grew up, they tended to overreact to social stress,
becoming so anxious and depressed that they wouldn’t even drink
sugar water. They avoided other mice as much as they could.
Dr. Nestler is not
sure exactly how the mouse fathers’ trauma communicates itself to
their offspring. It may be via sperm, or it may be through some more
complicated dance of nature and nurture that involves sperm but also
other factors. When instead of letting the “defeated” mice mate,
Dr. Nestler’s researchers killed them, harvested their sperm and
impregnated the female mice through artificial means, the offspring
were largely normal. Perhaps the sperm was harvested at the wrong
stage in the process, says Dr. Nestler. Or maybe the female mouse
picked up some signal when she had sex with the dysfunctional male
mouse, some telltale pheromone or squeak, that made her body withhold
nutrition and care from his pups. Females have been known to not
invest in the spawn of non-optimal males, an outcome that makes
perfect evolutionary sense — why waste resources on a loser?
When it comes to the
epigenetics of aging, however, there is little question that the
chemical insults and social setbacks of everyday life distill
themselves in sperm. A woman is born with all the eggs she’ll ever
carry. By the time a man turns 40, on the other hand, his gonad cells
will have divided 610 times to make spermatozoa. By the time he’s
in his 50s, that number goes up to 840. Each time those cells copy
themselves, mistakes may appear in the DNA chain. Some researchers
now think that a percentage of those mistakes reflects not just
random mutations but experience-based epigenetic markings that
insinuate themselves from sperm to fetus and influence brain
development. Another theory holds that aging gonad cells are more
error-prone because the parts of the DNA that should have spotted and
repaired any mistakes have been epigenetically tamped down. In any
case, we now know that the children of older fathers show more signs
ofschizophrenia, autism and bipolar disorder than
children of younger ones.
In a meta-analysis of
a population study of more than a million people published last year,
Christina Hultman of the Karolinska Institute of Sweden concluded
that children of men older than 50 were 2.2 times as likely to have
autism as children of 29-year-olds, even after the study had factored
out mothers’ ages and known risk factors for autism. By the time
the men passed 55, the risk doubled to 4.4 times that of
29-year-olds. Can the aging of the parent population explain the
apparent spike in autism cases? A study published last month in
Nature that used whole-genome sequencing on 78 Icelandic
families made the strongest case to date that as fathers age,
mutations in their sperm spike dramatically. Some of the mutations
found by the researchers in Reykjavik have been linked to autism and
schizophrenia in children.
In his Washington
Heights laboratory at the New York State Psychiatric Institute, Jay
Gingrich, a professor of psychobiology, compares the pups of young
male mice (3 months old or so) to those of old male mice (12 to 14
months old). The differences between the pups, he told me, weren’t
“earth-shattering” — they weighed about the same and there
weren’t big gaps in their early development. But discrepancies
appeared when the mice grew up. The adult offspring of the older
fathers had less adventuresome personalities; they also reacted to
loud noises in unusual ways that paralleled reactions evinced by
schizophrenics who heard similar sounds.
Still, Dr. Gingrich
said, “the differences were subtle” until he decided to pool the
data on their behavior and graph it on a bell curve. A “vast
majority” of the children of the older mice were “completely
normal,” he said, which meant their score fell under the
upside-down parabola of the curve. The real differences came at the
tails or skinny ends of the bell curve. There was about a sixfold
increase in likelihood that one of the “abnormal outliers,” mice
with cognitive or behavioral handicaps, “would come from an older
father.” Conversely, the super-high-performing mice were about six
times more likely to come from a younger father. “I’m an
inherently skeptical person,” Dr. Gingrich told me, but he was
impressed by these results.
One unanswered
question about autism and schizophrenia is how they crop up in
generation after generation; after all, wildly dysfunctional
individuals don’t usually flourish romantically. “I think we’re
going to have to consider that advanced paternal age, with its
epigenetic effects, may be a way of explaining the mysteries of
schizophrenia and autism, insofar as the rates of these disorders
have maintained themselves — and autism may be going up,” Dr.
Gingrich said. “From a cruel Darwinian perspective, it’s not
clear how much success these folks have at procreating, or how else
these genes maintain themselves in the population.”
When you’re an older
mother, you get used to the sidelong glances of sonogram technicians,
the extra battery of medical tests, the fear that your baby has Down
syndrome, the real or imagined hints from younger mothers that you’re
having children so late because you care more about professional
advancement than family. But as the research on paternal inheritance
piles up, the needle of doubt may swing at least partway to fathers.
“We’re living through a paradigm shift,” said Dolores
Malaspina, a professor ofpsychiatry at New York University who
has done pioneering work on older fathers and schizophrenia. Older
mothers no longer need to shoulder all the blame: “It’s the aging
man who damages the offspring.”
Aging, though, is only
one of the vicissitudes of life that assault a man’s reproductive
vitality. Think of epigenetics as having ushered in a new age of
sexual equality, in which both sexes have to worry about threats to
which women once felt uniquely exposed. Dr. Malaspina remembers that
before she went to medical school, she worked in a chemical plant
making radioactive drugs. The women who worked there came under
constant, invasive scrutiny, lest the toxic workplace contaminate
their eggs. But maybe, Dr. Malaspina points out, the plant managers
should have spared some concern for the men, whose germlines were
just as susceptible to poisoning as the women’s, and maybe even
more so. The well-being of the children used to be the sole
responsibility of their mothers. Now fathers have to be held
accountable, too. Having twice endured the self-scrutiny and
second-guessing that goes along with being pregnant, I wish them
luck.
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