If you’re worried that stupid people have more kids, don’t be (yet)
on
Get link
Facebook
X
Pinterest
Email
Other Apps
A tiny selection against education, but it's overwhelmed by cultural changes.
It’s a common perception that less-educated people have more children. The idea causes much hand-wringing and gnashing of teeth
over the possibility that human populations might become stupider over
the course of generations. But it’s actually pretty difficult to confirm
whether there really is a reproductive trend that would change the
genetic makeup of the human population overall.
Jonathan Beauchamp, a “genoeconomist” at
Harvard, is interested in questions at the intersection of genetics and
economics. He published a paper in PNAS
this week that provides some of the first evidence of evolution at the
genetic level in a reasonably contemporary human population. One of his
main findings is slight evolutionary selection for lower education—but
it’s really slight, just 1.5
months less of education per generation. Given that the last century has
seen vastly increased education across the globe, and around two years
extra per generation in the same time period as Beauchamp’s study, this
genetic selection is easily outweighed by cultural factors.
There are other important caveats to the
finding, most notably that Beauchamp only looks at a very small segment
of the global population: US citizens of European descent, born between
1931 and 1953. This means that we can’t generalize the results to, say,
China or Ghana, or even US citizens of non-European descent.
Based on this data, we also can’t say whether
people who have been of reproductive age at different times are subject
to similar forces. An evolutionary force that changes the course of our
species would need to be multi-generational, and this study doesn’t have
evidence of that. “The time span covered by Beauchamp is too short to
shed light on this question,” write Alexandre Courtiol, Felix C. Tropf,
and Melinda C. Mills in a PNAS commentary on Beauchamp’s project.
So why is it interesting? Well, it’s one of
the first forays into evolution in the contemporary human genome. There
has long been some muttering about whether humans are still evolving.
David Attenborough, for instance, has said that we’re not: “We stopped
natural selection as soon as we started being able to rear 95–99 percent
of our babies that are born,” he told Radio Times in an interview.
He was clearly wrong, though. Even if most
people survive into adulthood, evolution cares about one thing, and one
thing only: offspring. If people with certain genes have more children
than people with other genes, those genes proliferate, and that’s
evolution. Prior to the explosion in genetic data that’s currently
underway, however, we didn't have the data to say much about it.
Watching our genomes evolve
Previously, there have been studies exploring
how modern humans might be evolving, but those studies haven’t used
genetic data. They focused on a population, asking how many children
people in that population group have and whether certain characteristics
are related to having more or fewer children. Of course, it’s important
that the studies focus on characteristics where genetics play a role.
For instance, we know that genes (along with nutrition) play a role in
height, so if tall people have more children, we can assume that those
genes are becoming more common.
The problem with these studies is that they
don’t look at the genome itself. Evolution only happens when certain
genes are associated with having more children; in order to find
evidence of that evolution, it’s essential to go digging around in the
genome.
That’s what Beauchamp did, and he was one of the very first to do it, along with another group of researchers who published a paper
earlier this year. Their study looked at who people choose to marry and
reproduction across population groups. The data Beauchamp used
suggested that the effect on education was driven largely by people who
had no children at all, rather than by the difference between small and
large numbers of children.
It’s still a mystery what might be driving
this effect. There’s a huge amount we don’t understand about the links
between genes and people’s actual characteristics, note Courtiol, Tropf,
and Mills. People’s educational attainment does depend partly on
genetic traits, like intelligence and conscientiousness, but it’s still
unclear what exactly the genetic markers associated with education are
really doing when they help build and run a human. It’s possible they’re
influencing a number of different traits, and we don’t know which of
those results in people having more children.
The conclusion is tentative, but “the approach
is very interesting,” says Yair Field, a genetics researcher at
Stanford. “Given the growing availability of [data], this line of
research is likely to be followed and extended by further work in the
near future.”
“These studies mark a milestone in our
understanding of human evolution and natural selection in contemporary
populations,” write Courtiol, Tropf, and Mills. What would be ideal,
they say, is to have multi-generational studies that really allow us to
see whether certain genetic traits are becoming common in each
successive generation. This would be incredibly tricky—studies like
these need large amounts of nice, clean data, a better grasp of how
genes affect traits, and a good grasp on the role of culture. Still,
they write, “the question now shifts from whether or not natural
selection is present to an examination of its effects.”
Comments
Post a Comment