EMBARK | THE BIG IDEA
SCIENCE HAS SHOWN THAT YOU
ARE NOT WHO YOU THINK
YOU ARE. THERE ARE BIOLOGICAL
GREMLINS DRIVING EVERY
ACTION AND PERSONALITY
TRAIT THAT YOU ASSUMED WERE
OF YOUR OWN VOLITION.
Technically, yes. But embedded
within your genome, there are
many potential versions of you.
The person you see in the mirror
is just one of them, fished out by
the unique things you’ve been
exposed to since conception. The
new science of epigenetics is the
study of how chemical changes
made to DNA, or proteins that
interact with DNA, can affect gene
activity. DNA can be modified by
environmental factors in ways that
can profoundly affect development
and behavior. Recently, it’s also
been shown that the microbes in
your body—aka your microbiome—
can be a significant environmental
factor that affects myriad behav-
iors, from overeating to depression.
In sum, we are our genes—but our
genes cannot be evaluated outside
the context of our environment.
Genes are the piano keys, but the
environment plays the song. —BSAre you really just
a pile of genes?actions are governed by hidden biological forces—
which is to say that we have little or no control over
our personal tastes. Our behaviors and preferences
are profoundly influenced by our genetic makeup,
by factors in our environment that affect our genes,
and by other genes forced into our systems by the
innumerable microbes that dwell inside us.
I realize that this sounds ridiculous. We’re taught
that we can be whatever we want to be, do whatever
we want to do. Intuitively, it feels like we pick and
choose the foods we like, who we give our heart to, or
which buttons we press in the voting booth. To sug-
gest that we are just meat robots under the influence
of unseen forces is crazy talk!
Several years ago I would have agreed. But after
being grilled at one too many cookouts as to why I
don’t like many of the vegetables that most people
find enjoyable, I felt like something was wrong with
me. I am green with envy watching people willingly
eat things like broccoli, because if someone tries to
pass it to me, my body recoils in horror. Why don’t
I relish broccoli?
I wasn’t choosing to hate these vegetables, so I set
out to learn what could explain my aversion. Luckily,
science was on the case. Researchers have found that
about 25 percent of people might hate broccoli for the
same reason I do. These people—my people—are
called supertasters. We have variations in genes that
build our taste bud receptors. One of those genes,
TAS2R38, recognizes bitter chemicals like thioureas,
which are plentiful in broccoli. My DNA gives me taste
bud receptors that register thiourea compounds as
revoltingly bitter. This may be DNA’s way of deterring
me from eating harmful plants. It’s clearly the reason
that, as television’s Seinfeld character said of his fren-
emy Newman, I wouldn’t eat broccoli if it were deep
fried in chocolate sauce.THIS EXPLANATION of why I hate broccoli is both
vindicating and disturbing. I am relieved that my
distaste for cruciferous vegetables is not my fault—I
did not get to go gene shopping before I was con-
ceived. But the relief soon turns to alarm as I wonder:
What other things that define who I am are beyond
my command? How much of me is really due to me?
How about my taste in women? Surely that must
be under my control. Let’s start with the basics: Why
am I attracted to women instead of men? This was
not a conscious decision that I made while sitting on18 NATIONAL GEOGRAPHIC