F
or 10 years, geneticists have told the
story of how Neanderthals—or at least
their DNA sequences—live on in to-
day’s Europeans, Asians, and their de-
scendants. Not so in Africans, the story
goes, because modern humans and
our extinct cousins interbred only outside of
Africa. A new study overturns that notion,
revealing an unexpectedly large amount of
Neanderthal ancestry in modern popula-
tions across Africa. It suggests much of that
DNA came from Europeans migrating back
into Africa over the past 20,000 years.
“That gene flow with Neanderthals exists
in all modern humans, inside and outside of
Africa, is a novel and elegant
finding,” says anthropologist
Michael Petraglia of the Max
Planck Institute for the Sci-
ence of Human History. The
work, reported in this week’s
issue of Cell, could also help
clear up a mysterious dispar-
ity: why East Asians appear
to have more Neanderthal
ancestry than Europeans.
As members of Homo sa-
piens spread from Africa into
Eurasia some 70,000 years
ago, they met and mingled with Neander-
thals. Researchers knew that later back-
migrations of Europeans had introduced a
bit of Neanderthal DNA into African popu-
lations, but previous work suggested it was
a just a smidgen. In contrast, modern Euro-
peans and East Asians apparently inherited
about 2% of their DNA from Neanderthals.
Previous efforts simply assumed that Af-
ricans largely lacked Neanderthal DNA. To
get more reliable numbers, Princeton Uni-
versity evolutionary biologist Joshua Akey
compared the genome of a Neanderthal
from Russia’s Altai region in Siberia, se-
quenced in 2013, to 2504 modern genomes
uploaded to the 1000 Genomes Project, a
catalog of genomes from around the world
that includes five African subpopulations.
The researchers then calculated the prob-
ability that each stretch of DNA was inher-
ited from a Neanderthal ancestor.
The researchers found that African in-
dividuals on average had significantlymore Neanderthal DNA than previously
thought—about 17 megabases (Mb) worth,
or 0.3% of their genome. They also found
signs that a handful of Neanderthal genes
may have been selected for after they en-
tered Africans’ genomes, including genes
that boost immune function and protect
against ultraviolet radiation.
The results jibe with as-yet-unpublished
work by Sarah Tishkoff, an evolutionary ge-
neticist at the University of Pennsylvania.
She told Science she has also found higher-
than-expected levels of apparent Neander-
thal DNA in Africans.
The best fit model for where Africans
got all this Neanderthal DNA suggests
about half of it came when Europeans—
who had Neanderthal DNA
from previous matings—
migrated back to Africa in
the past 20,000 years. The
model suggests the rest of
the DNA shared by Africans
and the Altai Neanderthal
might not be Neanderthal
at all: Instead, it may be
DNA from early modern
humans that was simply re-
tained in both Africans and
Eurasians—and was picked
up by Neanderthals, per-
haps when moderns made a failed migra-
tion from Africa to the Middle East more
than 100,000 years ago.
Akey’s study might help explain another
“head scratcher,” says computer biologist
Kelley Harris of the University of Wash-
ington, Seattle. Studies had suggested
East Asians have 20% more Neanderthal
DNA than Europeans, she notes. “Europe
is where Neanderthal remains are found,
so why wouldn’t Europeans have more Ne-
anderthal ancestry than any other group?”
By suggesting that Europeans introduced
Neanderthal sequences into Africa, the new
study points to an explanation: Researchers
previously assumed that Neanderthal se-
quences shared by Europeans and Africans
were modern and subtracted them out. Af-
ter correcting for that bias, the new study
found similar amounts of Neanderthal DNA
in Europeans and Asians—51 and 55 Mb, re-
spectively. It’s a “convincing and elegant”
explanation, Harris says. jAncient Europeans took Neanderthal DNA back to Africa
HUMAN EVOLUTIONBy Michael PriceSCIENCE sciencemag.org 31 JANUARY 2020 • VOL 367 ISSUE 6477 497“Gene flow with
Neanderthals
exists in all modern
humans, inside and
outside of Africa ...”
Michael Petraglia,
Max Planck Institute for the
Science of Human Historymates, including many transgenic monkeys.
Poo hopes it will become an international
destination for primate neurobiology, akin
to CERN for the particle physics community.
“Scientifically it’s incredible,” Logothetis
says. “They have excellent groups work-
ing with CRISPR and genetic engineering.”
And, he adds, the acceptance of nonhuman
primate research by authorities and the
public in China is much higher than in Eu-
rope. They “know that no other brain (be-
sides that of humans themselves) can be a
true help in making progress.”
The move is another sign that China’s
investment in neuroscience research, es-
pecially involving primates, is paying off,
says Stefan Treue, director of the German
Primate Center. “China has made incredible
progress in an unbelievably short period of
time. That is the positive side of a political
system that is able to move very quickly.”
For nearly 2 decades Logothetis worked
primarily with macaques, sometimes im-
planting electrodes in their brains. In 2014,
a German TV program broadcast footage
from an undercover animal rights activist
showing one animal lame and vomiting and
another with blood on its head. Logothetis
and colleagues denied any wrongdoing and
said the video was misleading and staged.
But it triggered an investigation, includ-
ing a police raid on offices at the institute.
Logothetis received death threats. In 2015,
he said he would stop work with primates.
Initial legal investigations found no vio-
lation of animal regulations at his lab. But
in 2017, a Tübingen prosecutor charged that
Logothetis and two colleagues had violated
Germany’s animal protection laws by wait-
ing too long to euthanize ill monkeys. Max
Planck removed Logothetis from direct
oversight of animal research at the lab.
All charges against him and his colleagues
were later dropped and the society lifted
all restrictions on his leadership. During
the episode, major neuroscience organiza-
tions published open letters critical of Max
Planck’s handling of the situation.
Max Planck spokesperson Christina Beck
says Logothetis had already informed the
society of his move, but not the specific
timing. “It’s a pity that the vital discussion
about whether such research should be left
up only to China has been overshadowed by
the 2014 case,” she says.
Logothetis has been in negotiations with
Poo since at least 2018. All five group lead-
ers in his department plan to move with him,
he says, along with about half of the roughly
40 current lab members. Other international
researchers are considering ICPBR, he adds,
including several in Germany. j
With reporting by Dennis Normile in Shanghai.
Africans, too, carry Neanderthal
genetic legacy
Published by AAAS