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Over the last half
century, extreme
droughts and heavy rain
have become increas-
ingly common in the
countries that hug the
Andes. The mountain
chain, which stretches
along the western coast
of South America, blocks
incoming moisture and
wind from ocean cur-
rents. This drenches the
land on the seaside and
leaves the inland regions
in long dry spells.
We know that climate
change may affect these
currents, and we want to
prepare for the shifts in
weather. Computer mod-
els can help predict future
events, but data about
past fluctuations can
make the models more
robust and accurate.
So in 2011, my team
started creating an atlas
of the region’s floods and
dry spells going back 600
years. We collected
weather station logs, his-
torical newspapers, and
additional archival docu-
ments, but there were
many gaps. So we went
to nature’s own data-
base: We analyzed the
rings of more than 13,000
trees from the Andes,
drilling tiny cylindrical
holes into the trunks and
extracting samples of
their cores. Each layer
represents one year, and
its size can tell us about
conditions at the time.
Wet seasons allow for
growth spurts that create
wider bands, whereas
dry stretches produce
much thinner ones.
The final map is both a
time capsule and a tool
to forecast and with-
stand future swings.MARIANO MORALES,ENVIRONMENTAL SCIENTIST AT
THE ARGENTINIAN INSTITUTE OF SNOW SCIENCE,
GLACIOLOGY, AND ENVIRONMENTAL SCIENCES
as told to Sandra Gutierrez G.listening to trees
as told to Claire Maldarelliin the family
About half a million years in the past, modern humans
split from Neanderthals, our closest relatives. But when
the two species saw each other again 60,000 years
ago in what is now the Middle East, they interbred.
Those romances left their mark. In 2010, before I
started in the field, anthropologists sequenced the
Neanderthal genome using samples from fossilized
bones and found that parts of its DNA still exist in
humans. We now believe that more than 50 percent of
our evolutionary cousin’s genes have survived the millen-
nia, and we’re currently trying to understand why these
prehistoric chromosomes have persisted for so long—
and if they provide us with any evolutionary benefit.
In 2020, my lab found that a gene variant that en-
codes for a specific receptor for progesterone (a
hormone crucial to ensure healthy pregnancies) comes
from Neanderthals. It is present in one-third of Euro-
pean women, and those who possess it tend to have
fewer miscarriages and give birth to more children.
We’ve also found that some of the ancient hominin’s
genetic material seems to trigger an overactive immune
response to the novel coronavirus, resulting in a more
severe case of COVID-19. This troublesome gene likely
stuck around because it helped our ancestors fight dis-
ease, but now that we’ve identified it, we hope to
understand it and open the doors to future treatments.
Of course, the bits of Neanderthal living in each of us
aren’t all the same. About 1 to 2 percent of each hu-
man’s genome is Neanderthal in origin, and genetic
tests like 23andMe can reveal your number. I’ve still
never taken one, though I think it’s cool to know there’s
a little bit of our past within us all.HUGO ZEBERG,RESEARCHER AT THE MAX PLANCK
INSTITUTE FOR EVOLUTIONARY ANTHROPOLOGYTALESFROM THEFIELD