934 21 NOVEMBER 2014 • VOL 346 ISSUE 6212 sciencemag.org SCIENCE
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dark skin evolved into a sepia rainbow. It’s
a story Jablonski has told in countless radio
and TV interviews, two popular books, and
a TED talk viewed by nearly 700,000 people
online ( http://bit.ly/1tx8Jbs).
Although skin color is a poor way to clas-
sify humans, Jablonski says it does have real
implications for health. She argues that in
the modern era, as humans of various shades
have moved rapidly across hemispheres,
their skin has not had time to adapt to differ-
ent amounts of ultraviolet (UV) light. “You
have this lovely gradient of skin color—then,
people start moving around,” she says. “Of-
ten we’re unaware that we’re living in en-
vironments to which our skin is inherently
poorly adapted.”
Most white people know that if they live
near the equator, they risk skin cancer un-
less they use sunscreen. But Jablonski ar-
gues that other consequences of skin color
played crucial roles in its evolution. In the
tropics, she says, light-skinned people may
face a higher risk of having babies with
birth defects, because intense sunlight can
destroy folate in the blood. Meanwhile,
dark-skinned people who bundle up in
frigid northern winters or stay indoors all
day in the tropics risk vitamin D deficiency,
making them susceptible to rickets, infec-
tious diseases, heart disease, and other
health problems. “You can have a desk job
in Nairobi, or be a woman wearing the veil
in Yemen, or any number of fairly serious
scenarios where you don’t get enough vi-
tamin D,” Jablonski says. “This is an enor-
mous game changer for health.”
Some of Jablonski’s ideas remain un-
proven. Yet her work is injecting a shot of
evolutionary perspective into medicine and
influencing researchers to test how sunlight
affects health. Jablonski has “opened my eyes
to so many things I hadn’t thought about,”
says perinatal epidemiologist Lisa Bodnar of
the University of Pittsburgh in Pennsylvania.
Radiation epidemiologist Michael Kimlin of
the Queensland University of Technology in
Brisbane, Australia, agrees. “We have this
brand-new field in which people are sug-
gesting that when we put our bodies in the
sun, there are complex interactions,” he says.
“What Nina’s doing is not only contribut-
ing to evolutionary science … she’s creating
ripples in [biomedical] science and giving
people like me hypotheses to test.”
IF YOU HAD TOLD Jablonski when she was
a girl that she would travel the world giving lectures and be a sought-after speaker
on TV, she wouldn’t have believed it. Painfully shy, she grew up collecting butterflies
and fossils near her family’s farm, half a
mile from the nearest neighbor in western
New York. She flubbed her first organized
Shedding light on
SKIN COLOR
Nina Jablonski explores how it evolved—and what
happens when it does not match the environment
By Ann Gibbons
A few years ago, anthropologist Nina Jablonski faced off with comedian Stephen Colbert on his late-night alk show. He proclaimed that his kin was so white, he could hide in a snow bank. Was it really true, he
asked her, that his ancestors had dark skin?
Certainly, Jablonski said. If researchers
were to “dissect his DNA” they would find
evidence that he was descended from black
Africans. Colbert, in his conservative per-
sona, feigned shock: “Is it possible that I am
blacker than Barack Obama?”
In her 7 minutes on the show, Jablonski,
a biological anthropologist at Pennsylvania
State University (Penn State), University
Park, got her point across: “Skin color is
not about race,” she told Colbert. “It’s about
sun and how close our ancestors lived to the
equator.” As modern humans spread out of
Africa in the past 60,000 years, they adapted
to the varying natural light they encoun-
tered, from the twilight of northern winters
to the blazing sun of the equator, and their
