Neanderthals are thought to have disappeared in Europe approximately 39,000-41,000 years ago but they have contributed 1-3% of the DNA of present-day people in Eurasia. Here we analyse DNA from a 37,000-42,000-year-old modern human from Peştera cu Oase, Romania. Although the specimen contains small amounts of human DNA, we use an enrichment strategy to isolate sites that are informative about its…
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LETTER
doi:10.1038/nature14558
An early modern human from Romania with a recent
Neanderthal ancestor
Qiaomei Fu
1,2,3
*
, Mateja Hajdinjak
3
*
, Oana Teodora Moldovan
4
, Silviu Constantin
5
, Swapan Mallick
2,6,7
, Pontus Skoglund
2
,
Nick Patterson
6
, Nadin Rohland
2
, Iosif Lazaridis
2
, Birgit Nickel
3
, Bence Viola
3,7,8
, Kay Pru
̈
fer
3
, Matthias Meyer
3
, Janet Kelso
3
,
David Reich
2,6,9
& Svante Pa
̈
a
̈
bo
3
Neanderthals are thought to have disappeared in Europe approxi-
mately 39,000–41,000 years ago but they have contributed 1–3% of
the DNA of present-day people in Eurasia
1
. Here we analyse DNA
from a 37,000–42,000-year-old
2
modern human from Pes
̧tera cu
Oase, Romania. Although the specimen contains small amounts of
human DNA, we use an enrichment strategy to isolate sites that are
informative about its relationship to Neanderthals and present-
day humans. We find that on the order of 6–9% of the genome of
the Oase individual is derived from Neanderthals, more than any
other modern human sequenced to date. Three chromosomal seg-
ments of Neanderthal ancestry are over 50 centimorgans in size,
indicating that this individual had a Neanderthal ancestor as
recently as four to six generations back. However, the Oase indi-
vidual does not share more alleles with later Europeans than with
East Asians, suggesting that the Oase population did not contrib-
ute substantially to later humans in Europe.
Between 45,000 and 35,000 years ago, anatomically modern
humans spread across Europe, while the Neanderthals, present since
before 300,000 years ago, disappeared. How this process occurred
has long been debated
1,3–5
. Comparisons between the Neanderthal
genome and the genomes of present-day humans have shown that
Neanderthals contributed approximately 1–3% of the genomes of all
people living today outside sub-Saharan Africa
6,7
suggesting that
human populations ancestral to all non-Africans mixed with
Neanderthals. The size of segments of Neanderthal ancestry in
present-day humans suggests that this occurred between 37,000
and 86,000 years ago
8
. However, where and how often this occurred
is not understood. For example, Neanderthals share more alleles
with East Asians and Native Americans than with Europeans, which
may reflect additional interbreeding in the ancestors of eastern non-
Africans
9–12
. Surprisingly, analyses of present-day genomes have not
yielded any evidence that Neanderthals mixed with modern humans
in Europe, despite the fact that Neanderthals were numerous
there and cultural interactions between the two groups have been
proposed
13,14
.
More direct insight into the interactions between modern and
archaic humans can be obtained by studying genomes from modern
humans who lived at a time when they could have met Neanderthals.
Recent analyses of genomes from a
,
43,000–47,000-year-old modern
human from western Siberia
15
and a
,
36,000–39,000-year-old mod-
ern human from eastern Europe
16
showed that Neanderthal gene flow
into modern humans occurred before these individuals lived. The
Siberian individual’s genome contained some segments of
Neanderthal ancestry as large as 6 million base pairs (bp), suggesting
that some Neanderthal gene flow could have occurred a few thousand
years before his death
15
.
We report genome-wide data from a modern human mandible,
Oase 1, found in 2002 in the Pes
̧tera cu Oase, Romania. The age of
this specimen has been estimated to be
,
37,000–42,000 years by direct
radiocarbon dating
2,17,18
. Oase 1 is therefore one of the earliest modern
humans in Europe. Its morphology is generally modern but some
aspects are consistent with Neanderthal ancestry
19–21
. Subsequent
excavations uncovered a cranium from another, probably contempor-
aneous individual, Oase 2, which also carries morphological traits that
could reflect admixture with Neanderthals
17,19
.
We prepared two DNA extracts from 25 mg and 10 mg of bone
powder removed from the inferior right ramus of Oase 1. We treated
an aliquot of each of these extracts with
Escherichia coli
uracil-DNA
glycosylase (UDG), an enzyme that removes uracils from the interior
parts of DNA molecules, but leaves a proportion of uracils at the ends
of the molecules unaffected. Uracil residues occur in DNA molecules
as a result of deamination of cytosine residues, and are particularly
prevalent at the ends of ancient DNA molecules
9,22
. Among the DNA
fragments sequenced from these two extracts, 0.18% and 0.06%,
respectively, could be mapped to the human reference genome. We
prepared three additional DNA libraries from the extract containing
0.18% human-like molecules, but omitted the UDG treatment to
increase the number of molecules in which terminal C-to-T substitu-
tions could be seen and used to identify putatively ancient fragments.
Because the fraction of endogenous DNA is so small, we used hybrid-
ization to DNA probes to isolate human DNA fragments from the
libraries
23
. Applying this strategy to the mitochondrial genome
allowed the mitochondrial (mt)DNA from the five libraries to be
sequenced to an average coverage of 803-fold (Supplementary Note 1).
At the 3
9
ends of the DNA fragments, cytosine residues appeared as
thymine residues relative to the human mtDNA reference in 21% of
fragments, reflecting appreciable levels of cytosine deamination. This
suggests that at least some of the human mtDNA is of ancient origin.
We determined mtDNA consensus sequences in two ways: using all
mtDNA fragments, and using only deaminated fragments that carry
C-to-T substitutions at either end relative to the consensus mtDNA
sequence based on these fragments, an approach known to enrich
for endogenous DNA
9,24–26
. The mtDNA sequence based on all frag-
ments clusters with present-day Europeans (Extended Data Fig. 1)
(Supplementary Note 1). In contrast, the mtDNA sequence based on
deaminated fragments is related to a large group of present-day
Eurasian mtDNAs (haplogroup N) but diverges from these before
they diverged from each other. This Oase 1 mtDNA carries a few
private mutations on the basis of which its age can be estimated to
be 36,330 years before present (14,520–56,450; 95% confidence inter-
val). Using six positions at which the mtDNA sequence differs from at
least 99% of 311 present-day humans, we estimate the contamination
*
These authors contributed equally to this work.
1
Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, IVPP, CAS, Beijing 100044, China.
2
Department of Genetics, Harvard Medical School, Boston, Massachusetts
02115, USA.
3
Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
4
‘‘Emil Racovi ̧
ta
̆’’ Institute of Speleology, Cluj Branch, 400006 Cluj,
Romania.
5
‘‘Emil Racovi ̧
ta
̆’’ Institute of Speleology, Department of Geospeleology and Paleontology, 010986 Bucharest 12, Romania.
6
Broad Institute of MIT and Harvard, Cambridge, Massachusetts
02142, USA.
7
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
8
Department of Anthropology, University of Toronto, Toronto, Ontario, M5S
2S2, Canada.
9
Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, 02115, USA.
00 MONTH 2015 | VOL 000 | NATURE | 1
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2015
Macmillan Publishers Limited. All rights reserved
Page 2
among all mtDNA fragments to be 67% (95% confidence interval
65–69%). When we restrict to mtDNA fragments that carry terminal
C-to-T substitutions, the contamination estimate is 4% (95% confid-
ence interval of 2–9%) (Supplementary Note 1).
To isolate nuclear DNA from Oase 1, we used three sets of oligo-
nucleotide probes that cover about two million sites that are single
nucleotide polymorphisms (SNPs) in present-day humans and cap-
tured DNA molecules from the five libraries. Of the SNPs targeted,
51% (
n
5
1,038,619) were covered by at least one DNA fragment, and
13% (
n
5
271,326) were covered by at least one fragment with a
terminal C-to-T substitution. To estimate nuclear DNA contamina-
tion, we tested whether Oase 1 DNA fragments with or without evid-
ence of deamination share more alleles with present-day Europeans or
with East Asians. We found that Europeans share significantly fewer
alleles with Oase 1 fragments that are deaminated than with Oase 1
fragments that are not, consistent with European contamination of
17–30% (Supplementary Note 1). On the basis of these findings and
those from mtDNA, we restricted all subsequent analyses to DNA
fragments that carry terminal C-to-T substitutions. After doing this,
we found that we captured targeted SNPs from the X and Y chromo-
somes at a similar rate, indicating that Oase 1 carried both an X and a
Y chromosome and thus that he was male. The Y chromosome alleles
belong to the F haplogroup, which is carried by most males in Eurasia
today (Supplementary Note 2).
To determine the relationship of the Oase 1 individual to present-
day populations, we first tested whether he shared more alleles with
particular present-day individuals from different populations using
D
-statistics, which provides a robust estimate of admixture almost
regardless of how SNPs for analysis are chosen
27
. We find that
Oase 1 shared more alleles with present-day East Asians and Native
Americans than with present-day Europeans, counter to what might
naively be expected for an ancient individual from Europe (Fig. 1)
(5.2
#
j
Z
j
#
6.4; Extended Data Table 1). However, it has been sug-
gested that Europeans after the introduction of agriculture derive a
part of their ancestry from a ‘basal Eurasian’ population that separated
from the initial settlers of Europe and Asia before they split from
each other
28
. Therefore, we replaced present-day Europeans with
Palaeolithic and Mesolithic European individuals in these analyses.
We then find that the Oase 1 individual shares equally many alleles
with these early Europeans as with present-day East Asians and Native
Americans (Fig. 1) (
j
Z
j
#
1.5 inExtended Data Table 1). Restricting this
analysis to transversion polymorphisms, which are not susceptible to
errors induced by cytosine deamination, does not influence this result
(Extended Data Table 2 and Supplementary Note 3). This suggests that
the Oase 1 individual belonged to a population that did not contribute
much, or not at all, to later Europeans. This contrasts, for example, with
the
,
36,000–39,000-year-old Kostenki 14 individual from western
Russia, who was more closely related to later Europeans than to East
Asians (1.9
#
j
Z
j
#
13.7; Extended Data Table 1)
16
.
To assess whether the ancestors of the Oase 1 individual mixed with
Neanderthals, we tested whether the Altai Neanderthal genome shares
more alleles with the Oase 1 genome than with sub-Saharan Africans.
We find this to be the case (
j
Z
j
5
7.7; Supplementary Note 4). We then
asked whether the amount of Neanderthal ancestry in the Oase 1
genome is similar to that in present-day non-Africans. Surprisingly,
the Neanderthal genome shares more alleles with the Oase 1 individual
than it does with any present-day people in Eurasia that we tested,
indicating that he carries more Neanderthal-like DNA than present-
day people (5.0
#
j
Z
j
#
8.2; Extended Data Table 3). We also observe
more Neanderthal-like alleles in the Oase 1 individual when we com-
pare him to four early modern humans: an 8,000-year-old individual
from Luxembourg, and three individuals from Russia who vary in age
between 24,000 and 45,000 years (3.6
#
j
Z
j
#
6.8; Extended Data
Table 3). Thus, the Oase 1 individual appears to have carried more
Neanderthal-like DNA than any other modern human analysed to
date. This observation cannot be explained by residual present-day
human contamination among the DNA fragments that carry terminal
C-to-T substitutions, because all modern humans studied to date carry
less Neanderthal ancestry than the Oase 1 genome, and thus contam-
ination would lower, rather than increase, the apparent Neanderthal
ancestry.
We estimated the proportion of Neanderthal DNA in the Oase 1
genome using three different statistics
7,29
(Supplementary Note 4).
Although the results differ, they all yield point estimates between
6.0% and 9.4% (Table 1). For one of the statistics, none of the 90%
confidence intervals for Neanderthal ancestry in the other modern
Z
-score
Asian and
Native American
Asian
Native
American
6
4
2
0
–2
–4
–6
European
Western Eurasians before a
g
riculture
Loschbour
Kostenki 14
Ust’-Ishim
Loschbour
Kostenki 14
Ust’-Ishim
Figure 1
|
Allele sharing between the Oase 1 individual and other genomes.
Each point indicates the extent to which the Oase 1 genome shares alleles with
one or other of a pair of genomes from different populations indicated above
and below (see Extended Data Table 1 for numbers).
Z
-scores with an absolute
value greater than 2 indicate an excess of allele sharing (grey).
Table 1
|
Estimated fraction of the Oase 1 genome that derives from Neanderthals
Statistic 1
f
4
(
Denisova
,
Altai
;
Mbuti
,
X
)
f
4
(
Denisova
,
Altai
;
Mbuti
,
Mezmaiskaya
)
Statistic 2
1
{
f
4
(
Mbuti
,
Chimp
;
X
,
Denisova
)
f
4
(
Mbuti
,
Chimp
;
Dinka
,
Denisova
)
Statistic 3
f
4
(
X
,
Mbuti
;
Denisova
,
Chimp
)
f
4
(
Altai
,
Mbuti
;
Denisova
,
Chimp
)
Sample
Proportion
s.e.m.
90% CI
Proportion
s.e.m.
90% CI
Proportion
s.e.m.
90% CI
Oase 1
8.1%
2.0%
4.8–11.3%
9.4%
1.1%
7.5–11.3%
6.0%
2.0%
2.8–9.3%
Ust’-Ishim
3.6%
0.9%
2.2–5.0%
5.5%
0.7%
4.3–6.6%
0.4%
1.2%
0.0–2.5%
Kostenki 14
3.8%
1.0%
2.1–5.5%
2.9%
0.8%
1.6–4.2%
1.7%
1.3%
0.0–3.9%
MA1
1.2%
1.1%
0.0–3.0%
3.5%
0.8%
2.2–4.8%
2.3%
1.3%
0.1–4.5%
Loschbour
1.3%
0.9%
0.0–2.8%
3.9%
0.7%
2.7–5.1%
0.5%
1.2%
0.0–2.6%
La Bran
̃
a
3.1%
1.0%
1.4–4.7%
1.9%
0.7%
0.7–3.1%
1.4%
1.2%
0.0–3.4%
Stuttgart
3.0%
0.9%
1.5–4.4%
2.5%
0.7%
1.3–3.7%
0.4%
1.2%
0.0–2.4%
Han
2.2%
0.9%
0.6–3.7%
2.2%
0.8%
1.0–3.5%
1.0%
1.2%
0.0–3.1%
Dai
2.6%
0.9%
1.1–4.0%
1.0%
0.8%
0.0–2.3%
0.7%
1.2%
0.0–2.6%
French
3.0%
0.9%
1.6–4.5%
3.0%
0.7%
1.8–4.2%
0.2%
1.2%
0.0–2.2%
CI, confidence interval; s.e.m., standard error of the mean; negative values are truncated to 0%.
2 | NATURE | VOL 000 | 00 MONTH 2015
RESEARCH
LETTER
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Page 3
human samples overlap with the confidence interval in Oase 1. When
we restrict analysis to transversion SNPs, the point estimates of
Neanderthal ancestry are even higher (range of 8.4% to 11.3%)
(Extended Data Table 4).
To study the spatial distribution of Neanderthal DNA across the
Oase 1 genome, we designed capture probes for around 1.7 million
nucleotide positions at which nearly all individuals in a sub-Saharan
African population carry one allele whereas Neanderthal genomes
carry a different allele. We used these probes to isolate DNA fragments
from the Oase 1 individual. A total of 78,055 sites were covered by
deaminated DNA fragments from the Oase 1 individual and were also
covered by DNA fragments sequenced from the
,
36,000–39,000-
year-old Kostenki 14 individual from western Russia
16
, the
,
43,000–47,000-year-old individual from Ust’-Ishim in Siberia
15
,
and three present-day human genomes from China, France and
Sudan (Supplementary Note 5). Because the Dinka from Sudan are
thought to have little or no Neanderthal ancestry
7
, we subtracted the
number of alleles that match the Neanderthals in the Dinka individual
(485) from the number in the other genomes to estimate the number of
alleles attributable to Neanderthal ancestry. The resulting numbers of
putative Neanderthal alleles are 3,746 in the Oase 1 individual, 1,586
and 1,121 in the Ust’-Ishim and Kostenki 14 individuals, respectively,
and 1,322 and 1,033 in the Chinese and the European individuals
(Extended Data Table 5). Thus, the Neanderthal contribution to the
Oase 1 genome appears to be between 2.3- and 3.6-fold larger than to
the other genomes analysed. Assuming that the Neanderthal contri-
bution to the European individual is 2% (ref. 7), this suggests that 7.3%
of the Oase 1 genome is of Neanderthal origin. When the numbers of
alleles matching the Neanderthal genome are compared per chrom-
osome (Extended Data Table 5), the highest numbers are always
observed for the Oase 1 genome, except in the case of chromosome
21, in which the Ust’-Ishim individual carries a large segment of likely
Neanderthal ancestry.
We plotted the positions of Neanderthal-like alleles across the
Oase 1 genome (Fig. 2). We detect three segments that are over
50 centimorgans (cM) in size, suggesting that the Neanderthal contri-
bution to the Oase 1 individual occurred so recently in his family tree
that chromosomal segments of Neanderthal origin had little time to
break up due to recombination. To estimate the date of the most recent
Neanderthal contribution to the Oase 1 genome, we studied the size
spans of seven segments of the genome that appeared to be recently
derived from Neanderthals. Their genetic lengths suggest that the
Oase 1 individual had a Neanderthal ancestor as a fourth-, fifth- or
sixth-degree relative (Supplementary Note 5). This would predict that an
average of 1.6% to 6.3% of the Oase 1 genome derived from this recent
Neanderthal ancestor. Visual inspection of the Oase 1 genome sug-
gests that in addition to these seven segments, other smaller segments
also carry Neanderthal-like alleles (Fig. 2). When we remove the seven
longest segments, the estimate of Neanderthal ancestry in Oase 1 drops
from 7.3% to 4.8%, which is still around twice the 2.0–2.9% estimated
for the French, Han, Kostenki and Ust’-Ishim individuals in this
remaining part of the genome. This additional Neanderthal ancestry
1
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
O
U
K
H
F
D
0
50
100
150
200
0
50
100
150
050100
050100
050
0
50
050
050
050100
100
150
0
50
100
150
050100
050100
050
0
50
100
150
200
250
0
050
050100
050100
050
050
0
0
50
50
100
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100
150
50
100
150
200
250
2
3
4
5
6
7
9
10
12
13
14
8
11
15
16
17
18
19
20
21
22
Figure 2
|
Spatial distribution of alleles matching Neanderthals in modern
humans.
Coloured vertical lines indicate alleles shared with Neanderthals and
no colour indicates alleles shared with the great majority of West Africans.
D, Dinka; F, French; H, Han; K, Kostenki 14; O, Oase 1; U, Ust’-Ishim. The
seven grey bars indicate segments of putative recent Neanderthal ancestry. This
analysis is based on 78,055 sites. Numbers refer to chromosomes.
00 MONTH 2015 | VOL 000 | NATURE | 3
LETTER
RESEARCH
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2015
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