The science shows that human
nature is largely fixed, much to the chagrin of both left and right.
It’s
possible for humans to change. In recent centuries we’ve lived as
hunter-gatherers, as farmers, as factory workers, and as screen-absorbed
technology drones—among much else. Different cultures do things in radically
different ways even with the same technology. Specific individuals, too, change
over the course of their lives and act differently in different environments.
And
yet there are limits. Radical efforts at social engineering have resulted in
starvation and mass killings. While we don’t like to think about it, some
people seem naturally capable of things that others simply are not. As a
result, one of the biggest questions in politics is how greatly we can
reorganize and equalize society without bashing our heads into the limits of
nature.
t
Two
new books lay out the current science on human nature and human variation.
In The Ape That Understood the Universe, psychology professor Steve
Stewart-Williams explains the evolutionary roots that underlie many of our most
fundamental instincts and behaviors. And in Blueprint, behavioral
geneticist Robert Plomin lays out the wealth of evidence we have that
differences among individuals often boil down to differences in their DNA.
Together, they challenge major strains of liberal and conservative thought
alike.
♦♦♦
Stewart-Williams
begins with the very basics of evolution, paying special attention to the
“selfish gene” theory most famously articulated by Richard Dawkins.
Essentially, genes exist to replicate themselves, and those that do so most
efficiently are the ones that spread. They do this primarily by helping their
host—living things—survive, reproduce, and help their relatives reproduce, by
any means necessary. The life around us is the result of this process playing
out over millions of years, with changes introduced through random genetic
mutations and shaped by natural selection in each unique environment.
That’s
the part that annoys some conservatives. Here’s the part of Stewart-Williams’s
thinking that offends the Left: our brains, no less than our arms and our legs,
are the result of evolutionary processes. We are programmed with a suite of
instincts and urges that impel us to behave in ways that have been successful
for humans in the past. This includes not just the basic drives like hunger,
but also a lot of preferences and behavioral patterns that many would prefer to
see as mere outgrowths of culture, malleable as clothing styles. Perhaps most
controversially, it includes biological differences between the sexes.
Stewart-Williams’s
field, evolutionary psychology, has its share of critics—those who point out
that one can come up with an evolutionary “just-so story” to explain just about
anything humans do. But as Stewart-Williams shows, the essential findings of
evolutionary psychology have far stronger support than mere conjecture.
How
could we possibly know if a behavior is part of our very nature, instead of
springing from culture? One powerful indicator is whether it is a human
universal; if, in all the world, there is no society where something is
different, that suggests it may be hardwired. (This is especially true if it
persists despite cultural efforts against it.) Another is
whether our behaviors echo those found in other species facing similar
situations. And yet another is whether they have a clear connection to
evolutionary fitness—in other words, whether it’s the kind of thing that wouldevolve.
These
are the lenses through which Stewart-Williams looks at an astonishing variety
of human tendencies, carefully evaluating the theories and evidence as to how
they came about and sorting through the inevitable evolutionary riddles and
controversies—ranging from altruism to group selection to nepotism to sexual
attraction and jealousy. He also catalogues ways in which our evolved desires,
including our insatiable taste for sugar, can be an awkward and unfortunate fit
for the modern world.
And
of course, he spends some time on sex differences too, starting with a handy
list of 10 commonly found in nature and noting that many are found among humans
too. For instance, men are physically larger than women, have more interest in
casual sex, are more likely to “pay” for it (literally and figuratively), do
less child care, grow up more slowly, and don’t live as long. His thorough
exploration of these phenomena leaves little doubt that biology plays a role in
them.
But
all this focus on evolution doesn’t lead Stewart-Williams to neglect the power
of culture—quite the opposite, in fact. He notes that our sexual nature leaves
plenty of flexibility for different mating systems, from monogamy to polygamy
to casual flings. And the end of the book is dedicated to the concept of
“memes,” the ideas and practices that spread from person to person, from songs
to cooking techniques to scientific theories. These work similarly to genes in
a key way—if they don’t succeed in replicating themselves and spreading, they
die out—and yet their power reveals how much of the human experience is not hardwired,
but instead depends on what one’s fellow humans have been up to. And it turns
out that memes are the subject of a scientific literature considerably deeper
than one might expect.
This
is not a perfect book; in particular, some of the writing is a bit hokey,
including a lengthy exercise near the beginning in which we imagine aliens
coming to Earth to study the human species. But it’s worth getting over that.
Simply put, The Ape That Understood the Universe is a
thorough, readable, and indispensable guide to the human species and how it
operates.
♦♦♦
That’s
human nature, the basic configuration of our species as a whole. What about
human variation—the ways we differ from each other as individuals? Robert
Plomin is the guy to ask, as he’s a giant in the field of behavioral genetics.
He began his work in the 1970s, when the adoption- and twin-based studies that
form the field’s foundation were just taking off.
The
basic insights behind these studies are simple. Kids who are raised together
share much of their environment; they generally are raised by the same adults,
experience the same child care arrangements, enjoy the same material and health
benefits from the household’s income, go to the same schools, and so on.
Adopted siblings and twins, though, are unusual in how much of their genetic
material they have in common. While traditional siblings and fraternal twins
share about 50 percent of their genes, identical twins share virtually 100
percent and adopted siblings share none.
By
looking to see how much these siblings resemble each other, we can suss out the
relative contributions of genes, the “shared environment,” and other factors
(including random chance, parts of the environment that kids raised together
do not share, and simple measurement error). If adopted
siblings were just as similar as biological siblings, or if identical twins
were no more similar than fraternal twins, that would suggest that genes don’t
matter. But if adopted siblings were no more similar than strangers, or if
identical twins were exactly twice as similar as fraternal twins—mirroring the
fact that they share twice as much DNA—that would suggest that genes are the
only thing that make siblings alike.
When
it comes to psychological traits such as intelligence, personality, and
schizophrenia, the upshot is that the latter is closer to the truth: typically,
about half of the “variance” is explained by genes, while far less of it,
sometimes none, is explained by the shared environment. (The rest of it goes
into that catch-all third bin.) This implies that the things we put so much effort
into—parenting, schools, etc.—have relatively little impact, at least within
the normal range. (No one is saying that severe abuse or deprivation won’t
matter.) This has been known for decades, and formed the bedrock of Judith Rich
Harris’s 1998 classic The Nurture Assumption.
Also
long-established, if less widely discussed, is that even one’s environment is
actually partly genetic: we actively shape our surroundings in ways that suit
us. In one study, for instance, Plomin found that how much TV kids watch is
partly genetic. In others, researchers have found a genetic component to the
kinds of parenting that children receive. So research that, say, ties
TV-watching and parenting styles to academic outcomes may in part be measuring
kids’ genetics, not the effect of a bad family environment.
Over
the last couple of decades, Plomin and other researchers have started to shift
this research into the realm of DNA. The early results were not encouraging:
even though the twin and adoption studies said that psychological traits were
half-genetic or so, it was virtually impossible to find any genes that actually
made a difference. It turns out that these traits are controlled by thousands
of different genetic variants, each of which has only a minuscule effect. This
means you need a huge study, with thousands and thousands of participants, to
identify them statistically.
That’s
expensive, but it’s happening, and it’s showing results. Plomin and others are
finding boatloads of genes that affect important traits ranging from
educational attainment to depression, with each variant explaining, on average,
about 0.01 percent of the variance in the trait under study. And if you group a
bunch of these genes together you can calculate a “polygenic score” for an
individual—a number estimating his genetic endowment for that trait.
Since
these traits are about half-genetic, such a score could in theory explain half
the variance in them. So far, though, even the best ones top out around 10
percent. But that’s far from useless, so long as the scores are interpreted
with care: they’re not prophecies, but they do highlight risks, including for
mental illness. Someone with a bottom-tenth score for educational attainment,
for example, has a 32 percent chance of going to college, versus 70 percent for
someone in the top tenth. Plomin walks through some of his own polygenic
scores, which help to explain how he became an eminent scientist despite
growing up in a home with no books (he’s at the 94th percentile for educational
attainment) and why he has to work to control his weight (he’s also at the 94th
percentile for body mass index).
To
learn all this at the hands of a man who helped to jumpstart this field, and
who has pushed it forward into the modern era, ought to be a treat. To be blunt,
however, Blueprint is not nearly as good as it could or should
be. The writing gets just technical and clumsy enough that
members of the general public may often have a hard time following it. Those
better informed about the science, meanwhile, will learn little that’s new—and
may notice a number of troubling errors in Plomin’s descriptions of basic
statistical concepts, which I assume were the result of poor editing. (See
especially the butchering of p-values, regression to the mean, and confidence intervals.)
At
fewer than 200 pages (excluding the notes), it also doesn’t have room to
address some highly relevant topics. These include epigenetics, the process by
which genes are “expressed,” which some critics have presented as evidence of
the environment’s power (as environmental factors can turn genes on or off).
Also, a growing number of well-designed studies suggest that fairly normal
changes to a child’s social environment—say, going to preschool, receiving food
stamps, or moving to a different neighborhood—can have a sizable effect on his
outcomes years later, a finding hard to square with decades’ worth of
behavioral genetics claims that the “shared environment” is nearly toothless.
It would have been nice to see these angles addressed.
So,
this fascinating line of research still awaits a definitive explainer for the
average reader.
♦♦♦
These
two books are doubtlessly depressing to an extent. They suggest that in
important ways, humanity’s efforts to change itself are doomed to fail. We’re
simply not as malleable as we’d like. Neither the Left’s fantasies of extreme
social engineering nor the Right’s prized equal opportunity will give everyone
a fair shot at success.
But
there are encouraging signs as well. Stewart-Williams’s writing on memes shows the
power of ideas to change lives. And as Plomin notes, it’s not really clear why
we should find the power of DNA any more problematic than we’d find an
all-powerful environment.
One
fascinating study showed that when the USSR ended and Estonia became a freer
society, educational attainment and occupational status became more genetically
heritable—because people were newly able to follow their own desires and reach
their genetic potential. Would you rather be constrained by the situation you
grew up in, or by your own abilities?
Robert VerBruggen is a deputy managing editor of National
Review.
