More than 4,000 years ago, the Harappa culture thrived in the Indus
River Valley of what is now modern Pakistan and northwestern India,
where they built sophisticated cities, invented sewage systems that
predated ancient Rome's, and engaged in long-distance trade with
settlements in Mesopotamia. Yet by 1800 BCE, this advanced culture had
abandoned their cities, moving instead to smaller villages in the
Himalayan foothills.
A new study from the Woods Hole Oceanographic
Institution (WHOI) found evidence that climate change likely drove the
Harappans to resettle far away from the floodplains of the Indus.
Beginning in roughly 2500 BCE, a shift in temperatures and
weather patterns over the Indus valley caused summer monsoon rains to
gradually dry up, making agriculture difficult or impossible near
Harappan cities, says Liviu Giosan, a geologist at WHOI and lead author
on the paper that published Nov. 13, 2018, in the journal Climate of the Past.
"Although fickle summer monsoons made agriculture difficult along
the Indus, up in the foothills, moisture and rain would come more
regularly," Giosan says. "As winter storms from the Mediterranean hit
the Himalayas, they created rain on the Pakistan side, and fed little
streams there. Compared to the floods from monsoons that the Harappans
were used to seeing in the Indus, it would have been relatively little
water, but at least it would have been reliable."
Evidence for this shift in seasonal rainfall--and the Harapans'
switch from relying on Indus floods to rains near the Himalaya in order
to water crops--is difficult to find in soil samples. That's why Giosan
and his team focused on sediments from the ocean floor off Pakistan's
coast. After taking core samples at several sites in the Arabian Sea, he
and his group examined the shells of single-celled plankton called
foraminifera (or "forams") that they found in the sediments, helping
them understand which ones thrived in the summer, and which in winter.
Once he and the team identified the season based on the forams'
fossil remains, they were able to then focus on deeper clues to the
region's climate: paleo-DNA, fragments of ancient genetic material
preserved in the sediments.
"The seafloor near the mouth of the Indus is a very low-oxygen
environment, so whatever grows and dies in the water is very well
preserved in the sediment," says Giosan. "You can basically get
fragments of DNA of nearly anything that's lived there."
During winter monsoons, he notes, strong winds bring nutrients from
the deeper ocean to the surface, feeding a surge in plant and animal
life. Likewise, weaker winds other times of year provide fewer
nutrients, causing slightly less productivity in the waters offshore.
"The value of this approach is that it gives you a picture of the
past biodiversity that you'd miss by relying on skeletal remains or a
fossil record. And because we can sequence billions of DNA molecules in
parallel, it gives a very high-resolution picture of how the ecosystem
changed over time," adds William Orsi, paleontologist and geobiologist
at Ludwig Maximilian University of Munich, who collaborated with Giosan
on the work.
Sure enough, based on evidence from the DNA, the pair found that
winter monsoons seemed to become stronger--and summer monsoons
weaker--towards the later years of the Harappan civilization,
corresponding with the move from cities to villages.
"We don't know whether Harappan caravans moved toward the foothills
in a matter of months or this massive migration took place over
centuries. What we do know is that when it concluded, their urban way of
life ended," Giosan says.
The rains in the foothills seem to have been enough to hold the
rural Harapans over for the next millennium, but even those would
eventually dry up, likely contributing to their ultimate demise.
"We can't say that they disappeared entirely due to climate--at the
same time, the Indo-Aryan culture was arriving in the region with Iron
Age tools and horses and carts. But it's very likely that the winter
monsoon played a role," Giosan says.
The big surprise of the research, Giosan notes, is how far-flung the
roots of that climate change may have been. At the time, a "new ice
age" was settling in, forcing colder air down from the Arctic into the
Atlantic and northern Europe. That in turn pushed storms down into the
Mediterranean, leading to an upswing in winter monsoons over the Indus
valley.
"It's remarkable, and there's a powerful lesson for today," he
notes. "If you look at Syria and Africa, the migration out of those
areas has some roots in climate change. This is just the beginning--sea
level rise due to climate change can lead to huge migrations from low
lying regions like Bangladesh, or from hurricane-prone regions in the
southern U.S. Back then, the Harappans could cope with change by moving,
but today, you'll run into all sorts of borders. Political and social
convulsions can then follow."
UNM researchers part of discovery of ancient ancestry linking two continents
University of New Mexico
IMAGE: Excavation in progress at the rock shelter
site of Lapa do Santo in Brazil, where an individual dating to
approximately ~9,600 years ago was found.
view more
Credit: André Strauss
The first high quality ancient DNA data from Central and South
America--49 individuals some as old as 11,000 years--has revealed a
major and previously unknown exchanges between populations.
Unprecedented details about the ancestry of the people of Central
and South America have been uncovered in a new study in the journal Cell
by archaeologists and geneticists at The University of New Mexico,
Harvard Medical School, the Howard Hughes Medical Institute, the Max
Planck Institute for the Science of Human History, the University of
California Santa Cruz, the Pennsylvania State University, the University
of São Paulo, and other institutions in Brazil, Belize, Chile,
Argentina, Peru, the European Union and the U.S.
The researchers analyzed DNA data from precisely dated skeletons
found in excavations in Central and South America. Some of these people
were over 10,000 years old. Previously, the only genomes that had been
reported from this region and that provided sufficient quality data to
analyze were less than 1,000 years old.
After obtaining official permits to excavate, the researchers
conducted analysis on ancient human remains, and consulted with local
governmental agencies and indigenous organizations.
By comparing ancient and modern genomes from the Americas and other
parts of the globe, they were able to obtain qualitatively new insights
into the early history of Central and South America.
University of New Mexico Anthropology Professor Keith Prufer and his
colleagues from Pennsylvania State and Exeter University (UK)
contributed the Central American component of this unprecedented study
as part of an NSF and Alphawood Foundation funded project studying the
earliest humans to settle in the American tropics.
Prufer led excavations in Belize where the they recovered three of
the oldest skeletons from the region, all with well-preserved DNA.
This UNM project focuses on early human adaptations in remote
tropical rainforests in the Americas. The data from these excavations
are reshaping how researchers view Early Holocene relationships between
humans living in North, Central, and South America. Link between a Clovis culture-associated individual and the oldest Central and South Americans
"A key discovery was that a Clovis culture-associated individual
from North America dating to around 12,800 years ago shares distinctive
ancestry with the oldest Chilean, Brazilian and Belizean individuals,"
explains co-lead author Cosimo Posth of the Max Planck Institute for the
Science of Human History. "This supports the hypothesis that the
expansion of people who spread the Clovis culture in North America also
reached Central and South America."
These individuals from Chile, Brazil and Belize date to more than
9,000 years ago. However, younger individuals and present-day people in
South America do not share the Clovis culture-associated ancestry that
characterizes the oldest individuals. Says co-senior author David Reich
from Harvard Medical School and the Howard Hughes Medical Institute,
"This is our second key discovery: we have shown that there was a
continent-wide population replacement that began at least 9,000 years
ago."
According to Prufer, there are many remarkable aspects to this research finding.
"For the first time, we have archaeological and genetic evidence
linking some of the oldest humans in Central America to the earliest
known populations to arrive in the New World, and clear indications of
an early relationship between this region and South America," says
Prufer. "It is also a testament to the power of interdisciplinary
research involving archaeologists and geneticists and how it is
revolutionizing the study of ancient humans." The promise of ancient DNA research in the Americas
The researchers emphasize that their study gives only a glimpse of
the discoveries that may come through future work. To learn about the
initial movements of people into Central and South America, it would be
necessary to obtain ancient DNA from individuals dating to before 11,000
years ago.
Additionally, even for the period between 11,000 and 3,000 years ago
that is best covered in this study the picture is far from complete.
"We lacked ancient data from Amazonia, northern South America and
the Caribbean, and thus cannot determine how individuals in these
regions relate to the ones we analyzed," explains Reich. "Filling in
these gaps should be a priority for future work."
"We are excited about the potential of research in this area,"
states co-senior author Johannes Krause of the Max Planck Institute for
the Science of Human History. "With future, regionally focused studies
with large sample sizes, we could realize the potential of ancient DNA
to reveal how the human diversity of this region came to be the way it
is today."
Stone tools from the Middle Stone Age
in South Africa shows that different communities were connected over
long time periods over vast geographical areas.
University of the Witwatersrand
IMAGE: This is an overview of the Klipdrift Complex from sea.
view more
Credit: Magnus Haaland
The tools - mainly blades and backed knives from the Howiesons Poort -
were found in various layers in the Klipdrift Shelter, in the southern
Cape in South Africa. They were examined by a group of lithic experts,
who found distinct similarities to tools from sites in South Africa's
Western Cape, over 300km away, in particular with the Diepkloof Rock
Shelter site.
"While regional specificities in the tools from the various sites
exist, the similarities of Klipdrift Shelter with the site of Diepkloof
Rock Shelter are astonishing," says Dr Katja Douze, the corresponding
author of the study that was published in PLOS ONE on November
7. Douze is a researcher at the laboratory of Archaeology and
Populations in Africa at the University of Geneva, Switzerland. Douze
was a post-doctoral fellow at the Center of Excellence in Palaeosciences
at the Evolutionary Studies Institute, at University of the
Witwatersrand (Wits), at the time of the study. She led the analysis
together with Dr Anne Delagnes, Research Director at the French National
Center for Research (CNRS) and director of the laboratory PACEA, at the
University of Bordeaux, and with Dr Sarah Wurz, Associate professor at
the School of Geography, Archaeology and Environmental Sciences,
University of the Witwatersrand and also associated with the DST/NRF
SARChI Chair in The Origins of Modern Human Behaviour and the SapienCE -
Centre for Early Sapiens Behaviour (SFF CoE).
The team, under the leadership of Professor Christopher Henshilwood
from Wits University and the University of Bergen's SapienCE Centre for
Early Sapiens Behaviour, examined thousands of stone tools that were
excavated from seven layers that represent a time period of between 66
000 years ago and 59 000 years ago, to establish the differences in
stone tool design over time. They then also compared the stone tools to
various other sites in Howiesons Poort.
"The site of Klipdfrift Shelter is one of the few containing a long
archaeological sequence that provides data on cultural changes over time
during the Howiesons Poort," says Douze. "This makes it perfect to
study the change in culture over time."
However, what was even more exciting for the researchers was the
fact that for the first time they could show closely networked
interaction between distant communities through the way they designed
stone tools.
"There was an almost perfect match between the tools from the
Klipdrift and Diepkloof shelters," says Douze. "This shows us that there
was regular interaction between these two communities."
"This is the first time that we can draw such a parallel between
different sites based on robust sets of data, and show that there was
mobility between the two sites. This is unique for the Middle Stone
Age," says Douze.
The Middle Stone Age in Africa stretches from 350 000 years ago to
25 000 years ago and is a key period for understanding the development
of the first Homo sapiens, their behavioral changes through time and
their movements in-and-out of Africa.
Named after Howieson's Poort Shelter archeological site near
Grahamstown in South Africa, the Howiesons Poort is a specific
techno-culture within the Middle Stone Age that evolves in southern
Africa after 100 000 years ago at the Diepkloof Shelter, but between 66
000 - 59 000 years at most other Howiesons Poort sites. The
characteristics of the Howiesons Poort are strongly distinctive from
other Middle Stone Age industries as it is characterised by the
production of small blades and backed tools, used as hunting armatures
as much as for cutting flesh, while other MSA industries show flake,
large blade and point productions.
The tools found in the deeper layers of the Klipdrift Shelter that
represent the earlier phases of the Howiesons Poort were found to be
made from heat-treated silcrete, while those from later phases were made
from less homogeneous rocks such as quartz and quartzite. This change
happens together with changes in tool production strategies. "The
changes over time seems to reflect cultural changes, rather than
immediate alterations forced on the designers by changes in climate",
says Douze.
"Our preconceived idea of prehistoric groups is that they just
struggled to survive, but in fact they were very adaptable to
environmental circumstances. There seem to be no synchrony between
modification in design choices and environmental changes. However, the
aridification of the area over time might have led to a very gradual
change that led to the end of the Howiesons Poort."
The team also attempted to establish why and how the Howiesons Poort
ended, and to see whether it came to a sudden, or gradual end.
"The decline of the Howiesons Poort at Klipdrift Shelter shows a
gradual and complex pattern of changes, from which the first "symptoms"
can be observed much earlier than the final abandonment of typical
Howiesons Poort technology and toolkits," says Douze.
"This does not support a catastrophic scenario involving alarming
demographic drops or massive population replacements. The fact that a
similar pattern of gradual change has been described for at least three
other southern African Howiesons Poort sites (Rose Cottage Cave,
Diepkloof Rock Shelter and Klasies River main site), further ascertains
convergent evolutions in cultural trajectories rather than isolated
groups promptly reacting to locally determined pressures."
Study by 72 researchers from eight
countries concludes that the Lagoa Santa people are descendants of
Clovis culture migrants from North America; distinctly African features
attributed to Luzia were wrong
Fundação de Amparo à Pesquisa do Estado de São Paulo
IMAGE: Study by 72 researchers from eight
countries concludes that the Lagoa Santa people are descendants of
Clovis culture migrants from North America. Distinctly African features
attributed to Luzia were wrong
view more
Credit: André Strauss e Caroline Wilkinson
The history of the peopling of the Americas has just been
interpreted afresh. The largest and most comprehensive study ever
conducted on the basis of fossil DNA extracted from ancient human
remains found on the continent has confirmed the existence of a single
ancestral population for all Amerindian ethnic groups, past and present.
Over 17,000 years ago this original contingent crossed the Bering
Strait from Siberia to Alaska and began peopling the New World. Fossil
DNA shows an affinity between this migratory current and the populations
of Siberia and northern China. Contrary to the traditional theory it
had no link to Africa or Australasia.
The new study also reveals that once they had settled in North
America the descendants of this ancestral migratory flow diversified
into two lineages some 16,000 years ago.
The members of one lineage crossed the Isthmus of Panama and peopled South America in three distinct consecutive waves.
The first wave occurred between 15,000 and 11,000 years ago. The
second took place at most 9,000 years ago. There are fossil DNA records
from both migrations throughout South America. The third wave is much
more recent but its influence is limited as it occurred 4,200 years ago.
Its members settled in the Central Andes.
An article on the study has just been published in the journal Cell
a group of 72 researchers from eight countries, affiliated with the
University of São Paulo (USP) in Brazil, Harvard University in the
United States, and Max Planck Institute for the Science of Human History
in Germany, among others.
According to the researchers' findings, the lineage that made the
north-south journey between 16,000 and 15,000 years ago belonged to the
Clovis culture, named for a group of archeological sites excavated in
the western US and dating from 13,500-11,000 years ago.
The Clovis culture was so named when flint spearheads were found in
the 1930s at a dig in Clovis, New Mexico. Clovis sites have been
identified throughout the US and in Mexico and Central America. In North
America, the Clovis people hunted Pleistocene megafaunas such as giant
sloth and mammoth. With the decline of the megafauna and its extinction
11,000 years ago, the Clovis culture eventually disappeared. Long before
that, however, bands of hunter-gatherers had traveled south to explore
new hunting grounds. They ended up settling in Central America, as
evidenced by 9,400-year-old human fossil DNA found in Belize and
analyzed in the new study.
At a later date, perhaps while pursuing herds of mastodons, Clovis
hunter-gatherers crossed the Isthmus of Panama and spread into South
America, as evidenced by genetic records from burial sites in Brazil and
Chile revealed now. This genetic evidence corroborates well-known
archeological finds such as the Monte Verde site in southern Chile,
where humans butchered mastodons 14,800 years ago.
Among the many known Clovis sites, the only burial site associated
with Clovis tools is in Montana, where the remains of a baby boy
(Anzick-1) were found and dated to 12,600 years ago. DNA extracted from
these bones has links to DNA from skeletons of people who lived between
10,000 and 9,000 years ago in caves near Lagoa Santa, Minas Gerais
State, Brazil. In other words, the Lagoa Santa people were partial
descendants of Clovis migrants from North America.
"From the genetic standpoint, the Lagoa Santa people are descendants of the first Amerindians," said archeologist André Menezes Strauss,
who coordinated the Brazilian part of the study. Strauss is affiliated
with the University of São Paulo's Museum of Archeology and Ethnology
(MAE-USP).
"Surprisingly, the members of this first lineage of South Americans
left no identifiable descendants among today's Amerindians," he said.
"Some 9,000 years ago their DNA disappears completely from the fossil
samples and is replaced by DNA from the first migratory wave, prior to
the Clovis culture. All living Amerindians are descendants of this first
wave. We don't yet know why the genetic stock of the Lagoa Santa people
disappeared."
One possible reason for the disappearance of DNA from the second
migration is that it was diluted in the DNA of the Amerindians who are
descendants of the first wave and cannot be identified by existing
methods of genetic analysis.
According to Tábita Hünemeier,
a geneticist at the University of São Paulo's Bioscience Institute
(IB-USP) who took part in the research, "one of the main results of the
study was the identification of Luzia's people as genetically related to
the Clovis culture, which dismantles the idea of two biological
components and the possibility that there were two migrations to the
Americas, one with African traits and the other with Asian traits".
"Luzia's people must have resulted from a migratory wave originating
in Beringia," she said, referring to the now-submerged Bering land
bridge that joined Siberia to Alaska during the glaciations, when sea
levels were lower.
"The molecular data suggests population substitution in South
America since 9,000 years ago. Luzia's people disappeared and were
replaced by the Amerindians alive today, although both had a common
origin in Beringia," Hünemeier said. Brazilian contribution
The Brazilian researchers' contribution to the study was
fundamental. Among the 49 individuals from which fossil DNA was taken,
seven skeletons dated to between 10,100 and 9,100 years ago came from
Lapa do Santo, a rock shelter in Lagoa Santa.
The seven skeletons, alongside dozens of others, were found and
exhumed in successive archeological campaigns at the site, led initially
by Walter Alves Neves,
a physical anthropologist at IB-USP, and since 2011 by Strauss. The
archeological campaigns led by Neves between 2002 and 2008 were funded
by São Paulo Research Foundation - FAPESP.
Altogether the new study investigated fossil DNA from 49 individuals
found at 15 archeological sites in Argentina (two sites, 11 individuals
dated to between 8,900 and 6,600 years ago), Belize (one site, three
individuals dated to between 9,400 and 7,300 years ago), Brazil (four
sites, 15 individuals dated to between 10,100 and 1,000 years ago),
Chile (three sites, five individuals dated to between 11,100 and 540
years ago) and Peru (seven sites, 15 individuals dated to between 10,100
and 730 years ago).
The Brazilian skeletons come from the archeological sites Lapa do
Santo (seven individuals dated to about 9,600 years ago), Jabuticabeira
II in Santa Catarina State (a sambaqui or shell midden with five
individuals dated to about 2,000 years ago), as well as from two river
middens in the Ribeira Valley, São Paulo State: Laranjal (two
individuals dated to about 6,700 years ago), and Moraes (one individual
dated to about 5,800 years ago). Paulo Antônio Dantas de Blasis, an archeologist affiliated with MAE-USP, led the dig at Jabuticabeira II, which was also supported by FAPESP through a Thematic Project.
The digs at the river midden sites in São Paulo State were led by Levy Figuti, also an archeologist at MAE-USP, and were also supported by FAPESP.
"The Moraes skeleton (5,800 years old) and the Laranjal skeleton
(6,700 years old) are among the most ancient from the South and
Southeast of Brazil," Figuti said. "These locations are strategically
unique because they're between the highlands of the Atlantic plateau and
the coastal plain, contributing significantly to our understanding of
how the Southeast of Brazil was peopled."
These skeletons were found between 2000 and 2005. From the start,
they presented a complex mixture of coastal and inland cultural traits,
and the results of their analysis generally varied except in the case of
one skeleton diagnosed as Paleoindian (analysis of its DNA is not yet
complete).
"The study that's just been published represents a major step
forward in archeological research, exponentially increasing what we knew
until only a few years ago about the archaeogenetics of the peopling of
the Americas," Figuti said.
Hünemeier has also recently made a significant contribution to the
reconstruction of human history in South America using paleogenomics. Amerindian genetics
Not all the human remains found at some of the most ancient
archeological sites in Central and South America belonged to genetic
descendants of the Clovis culture. The inhabitants of several sites did
not have Clovis-associated DNA.
"This shows that besides its genetic contribution the second
migration wave to South America, which was Clovis-associated, may also
have brought with it technological principles that would be expressed in
the famous fishtail points that are found in many parts of South
America," Strauss said.
How many human migrations from Asia came to the Americas at the end
of the Ice Age more than 16,000 years ago was hitherto unknown. The
traditional theory, formulated in the 1980s by Neves and other
researchers, was that the first wave had African traits or traits
similar to those of the Australian Aboriginals.
The well-known forensic facial reconstruction of Luzia was performed
in accordance with this theory. Luzia is the name given to the fossil
skull of a woman who lived in the Lagoa Santa region 12,500 years ago
and is sometimes referred to as the "first Brazilian".
The bust of Luzia with African features was built on the basis of
the skull's morphology by British anatomical artist Richard Neave in the
1990s.
"However, skull shape isn't a reliable marker of ancestrality or
geographic origin. Genetics is the best basis for this type of
inference," Strauss explained.
"The genetic results of the new study show categorically that there
was no significant connection between the Lagoa Santa people and groups
from Africa or Australia. So the hypothesis that Luzia's people derived
from a migratory wave prior to the ancestors of today's Amerindians has
been disproved. On the contrary, the DNA shows that Luzia's people were
entirely Amerindian."
A new bust has replaced Luzia in the Brazilian scientific pantheon.
Caroline Wilkinson, a forensic anthropologist at Liverpool John Moores
University in the UK and a disciple of Neave, has produced a facial
reconstruction of one of the individuals exhumed at Lapa do Santo. The
reconstruction was based on a retrodeformed digital model of the skull.
"Accustomed as we are to the traditional facial reconstruction of
Luzia with strongly African features, this new facial reconstruction
reflects the physiognomy of the first inhabitants of Brazil far more
accurately, displaying the generalized and indistinct features from
which the great Amerindian diversity was established over thousands of
years," Strauss said.
The study published in Cell, he added, also presents the first genetic data on Brazilian coastal sambaquis.
"These monumental shell mounds were built some 2,000 years ago by
populous societies that lived on the coast of Brazil. Analysis of fossil
DNA from shell mound burials in Santa Catarina and São Paulo shows
these groups were genetically akin to the Amerindians alive today in the
South of Brazil, especially the Kaingang groups," he said.
According to Strauss, DNA extraction from fossils is technically
very challenging, especially if the material was found at a site with a
tropical climate. For almost two decades extreme fragmentation and
significant contamination prevented different research groups from
successfully extracting genetic material from the bones found at Lagoa
Santa.
This has now been done thanks to methodological advances developed
by the Max Planck Institute. As Strauss enthusiastically explained, much
more remains to be discovered.
"Construction of Brazil's first archaeogenetic laboratory is
scheduled to begin in 2019, thanks to a partnership between the
University of São Paulo's Museum of Archeology and Ethnology (MAE) and
its Bioscience Institute (IB) with funding from FAPESP. When it's ready,
it will give a new thrust to research on the peopling of South America
and Brazil," Strauss said.
"To some extent, this study not only changes what we know about how
the region was peopled but also changes considerably how we study human
skeletal remains," Figuti said.
Human remains were first found in Lagoa Santa in 1844, when Danish
naturalist Peter Wilhelm Lund (1801-1880) discovered some 30 skeletons
deep in a flooded cave. Almost all these fossils are now at the Natural
History Museum of Denmark in Copenhagen. A single skull has stayed in
Brazil. It was donated by Lund to the Brazilian History and Geography
Institute in Rio de Janeiro. Colonization by leaps and bounds
On the same day as the Cell article was published (November 8, 2018), a paper in the journal Science also reported new findings on fossil DNA from the first migrants to the Americas. André Strauss is one of the authors.
Among the 15 ancient skeletons from which genetic material was
taken, five belong to the Lund Collection in Copenhagen. They date from
between 10,400 and 9,800 years ago. They are the oldest in the sample,
alongside an individual from Nevada estimated to be 10,700 years old.
The sample comprised fossilized human remains from Alaska, Canada,
Brazil, Chile, and Argentina. The results of its molecular analysis
suggested the peopling of the Americas by the first human groups out of
Alaska did not come about merely through gradual occupation of territory
concomitantly with population growth.
According to the researchers responsible for the study, the
molecular data suggests that the first humans to invade Alaska or
neighboring Yukon, split into two groups. This happened between 17,500
and 14,600 years ago. One group colonized North and Central America, the
other South America.
The peopling of the Americas ensued by leaps and bounds, as small
bands of hunter-gatherers traveled far and wide to settle in new areas
until they reached Tierra del Fuego in a movement lasting one or at most
two millennia.
Among the 15 individuals whose DNA was analyzed, three of the Lagoa
Santa five were found to have some genetic material from Australasia, as
suggested by the theory proposed by Neves for the occupation of South
America. The researchers are unable to explain the origin of this
Australasian DNA or how it ended up in only a few of the Lagoa Santa
people.
"The fact that the genomic signature of Australasia has been present
for 10,400 years in Brazil but is absent in all the genomes tested to
date, which are as old or older, and found farther north, is a challenge
considering its presence in Lagoa Santa," they said.
Other fossils collected during the twentieth century include the
Luzia skull, found in the 1970s. Almost 100 skulls excavated by Neves
and Strauss in the past 15 years are now held at USP. A similar number
of fossils are held at the Pontifical Catholic University of Minas
Gerais (PUC-MG).
But the vast majority of these osteological and archeological
treasures, belonging to perhaps more than 100 individuals, were
deposited at the National Museum in Rio de Janeiro and were presumably
destroyed in the fire that raged through this historic building on
September 2, 2018.
The Luzia skull was on display at the National Museum alongside
Neave's facial reconstruction. Scientists feared it had been lost to the
fire but fortunately it was one of the first objects to be recovered
from the ruins. It had broken up but survived. The fire destroyed the
original facial reconstruction (of which there are several copies).
IMAGE: This visual abstract depicts the findings of Posth et al.,
who conducted a large-scale analysis of ancient genomes from Central
and South America yields insights into the peopling of the...
view more
Credit: Posth et al./Cell
An international research team has used genome-wide ancient DNA data
to revise Central and South American history. Their analysis of DNA
from 49 individuals spanning about 10,000 years in Belize, Brazil, the
Central Andes, and southern South America has concluded that the
majority of Central and South American ancestry arrived from at least
three different streams of people entering from North America, all
arising from one ancestral lineage of migrants who crossed the Bering
Strait some time before 15,000 years ago.
The evidence, presented November 8 in the journal Cell,
shows that within this one ancestral lineage, there were two previously
undocumented streams of gene flow from North to South America, one of
which was later displaced in a major population replacement that began
at least 9,000 years ago.
"Our work multiplied the number of ancient genomes available from
these areas by about 20, giving us a much more comprehensive picture of
indigenous history in the Americas," says co-senior author David Reich, a
geneticist at Harvard Medical School and the Howard Hughes Medical
Institute. "This broader dataset reveals a common origin of North,
Central, and South Americans as well as two previously unknown genetic
exchanges between North and South America."
"Nearly all Central and South Americans arose from a star-like
radiation of the first lineage into at least three branches," says
co-lead author Cosimo Posth, an archaeogeneticist from the Max Planck
Institute for the Science of Human History. "That means that nearly all
the ancestry of Central and South Americans came from the same source
population, albeit one that had already diversified prior to its spread
into South America. With DNA evidence largely based on present-day
people, those multiple gene flow events are undetectable, highlighting
the power of ancient DNA data."
The genome analysis also yielded new insights on the Clovis
culture-related people, who were mainly distributed across North America
from about 13,000 years ago. Archaeological evidence from Clovis sites
shows that the spread of Clovis artefacts did not expand throughout
South America. But when the researchers used genome-sequencing
technology to generate and compare genomes from a previously published
~13,000-year-old Clovis-related genome in Montana to the earliest
genomes analyzed from South and Central America dating to between ~9,000
and ~11,000 years ago, they noticed significant shared ancestry. That
suggested that the people who spread the Clovis culture also left a
major impact much father south through people producing
non-Clovis-specific stone tools.
"We weren't expecting to find a relation to people associated with
the Clovis culture in South America," says co-first author Nathan
Nakatsuka, a PhD student in Reich's lab at Harvard. "But it seems the
expansion of the Clovis-associated lineage extended to parts of Central
and South America."
The paper concludes that this Clovis-related lineage contributed
substantially to a group of 9,000-10,000-year-old individuals from Lagoa
Santa in Brazil, inconsistent with the hypothesis that the people from
this site derived from a separate migration from Asia. The authors also
detected the Clovis-related genetic affinity in an even older, almost
~11,000-year-old individual from Chile and a slightly younger, more than
~9,000-year-old individual from Belize.
Beginning around ~9,000 years ago with ancient samples in Peru,
however, the authors detected an almost complete disappearance of the
Clovis culture-associated ancestry in Central and South America,
documenting a remarkable population replacement. The large-scale
population replacement is a process that was not widely expected by
archaeologists," says Reich. "This is an exciting example of how ancient
DNA studies can reveal events in the past that were not confirmed and
thus can stimulate new work in archaeology."
The researchers also showed that after this major population
turnover, there was striking continuity compared to other parts of the
world like Eurasia and Africa. "There is remarkable continuity between
earlier and later skeletons with South Americans today," says Posth.
"For example, modern-day Quechua and Aymara from the Central Andes can
trace their ancestry back to the ancient people of the Cuncaicha site
from 9,000 years ago onwards. This is a longer-standing continuity than
you see in other continents."
The researchers recognize that there is much more work to do to fully flesh out the history of the Americas.
"We're very enthusiastic about the prospects for a much richer
understanding of American population history, but this is still a vast
region full of geographic and chronological holes," says Reich. "We'd
like to collect more genetic material from earlier and later sites and
from more countries, such as Colombia, Venezuela, and other parts of
Brazil. We also want to examine the evolution of genetic traits over
time."
Adaptations to the harsh environment spare Andean highlanders from complete devastation due to European contact
University of Chicago Medical Center
IMAGE: This is the location of ancient samples near Lake Titicaca, elevation 3812 meters, in what is now Peru and Bolivia.
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Credit: Authors of the study
A multi-center study of the genetic remains of people who settled
thousands of years ago in the Andes Mountains of South America reveals a
complex picture of human adaptation from early settlement, to a split
about 9,000 years ago between high and lowland populations, to the
devastating exposure to European disease in the 16th-century colonial
period.
Led by Anna Di Rienzo, PhD, and John Lindo, PhD, JD, from the
University of Chicago; Mark Aldenderfer, PhD, from the University of
California, Merced; and Ricardo Verdugo from the University of Chile,
the researchers used newly available samples of DNA from seven whole
genomes to study how ancient Andean people--including groups that
clustered around Lake Titicaca in Peru and Bolivia, 12,000 feet above
sea level--adapted to their environment over the centuries.
In the journal Science Advances, they compared their seven
historical genomes to 64 modern-day genomes from a current highland
Andean population, the agropastoral Aymara of Bolivia, and the lowland
hunter-gatherer Huilliche-Pehuenche in coastal Chile.
The goals were (1) to date the initial migration to the Andean
highlands, (2) to identify the genetic adaptations to the high-altitude
environment that allowed that settlement, (3) to estimate the impact of
the European contact starting in the 1530s that caused the near
annihilation of many lowland communities of South America.
"We have very ancient samples from the high Andes," said Di Rienzo.
"Those early settlers have the closest affinity to the people who now
live in that area. This is a harsh, cold, resource-poor environment,
with low oxygen levels, but people there adapted to that habitat and the
agrarian lifestyle."
The study, "The Genetic prehistory of the Andean highlands 7,000
years BP through European contact," uncovered several unexpected
features.
The researchers found that highland Andeans experienced much smaller
than expected population declines following contact with European
explorers who first came to South America in the 1530s. In the lowlands,
demographic modeling and historical records infer that up to 90 percent
of residents may have been wiped-out after the arrival of Europeans.
But the people living in the upper Andes had only a 27-percent
population reduction.
Even though the highlanders lived in altitudes above 8,000 feet,
which meant reduced oxygen, frequent frigid temperatures and intense
ultra-violet radiation, they did not develop the responses to hypoxia
seen in natives of other high-altitude settings, such as Tibet.
The Andeans may have adapted to high altitude hypoxia "in a
different way, via cardiovascular modifications," the researchers
suggest. They found evidence of alterations in a gene called DST, which
is associated with the formation of cardiac muscle. Andean highlanders
tend to have enlarged right ventricles. This may have improved oxygen
intake, enhancing blood flow to the lungs.
But the strongest adaptation signal the researchers found was in a
gene called MGAM (maltase-glucoamylase) an intestinal enzyme. It plays
an important role in the digestion of starchy foods such as potatoes--a
food native to the Andes. A recent study suggests that the potato may
have been domesticated in the region at least 5,000 years ago. Positive
selection on the MGAM gene, the authors note, "may represent an adaptive
response to greater reliance upon starchy domesticates."
The early presence of this variant in Andean peoples suggests "a
significant shift in diet from one that was likely more meat based to
one more plant based," said UC Merced's Aldenderfer, an anthropologist.
"The timing of the appearance of the variant is quite consistent with
what we know of the paleo-ethno-botanical record in the highlands."
Although Andean settlers consumed a high-starch diet after they
started to farm, their genomes did not develop additional copies of the
starch related amylase gene, commonly seen in European farming
populations.
A comparison of the ancient genomes with their living descendants
also revealed selection for immune-related genes soon after the arrival
of Europeans, suggesting that Andeans who survived may have had an
advantage with regard to the newly introduced European pathogens.
"Contact with Europeans had a devastating impact on South American
populations, such as the introduction of disease, war, and social
disruption," explained Lindo. "By focusing on the period before that, we
were able to distinguish environmental adaptations from adaptations
that stemmed from historical events."
"In our paper," said Aldenderfer, "there was none of this
prioritization of genes at the expense of archaeological data. We worked
back and forth, genetics and archeology, to create a narrative
consistent with all of the data at hand."
Research on a newly rediscovered 9,000-year-old child's tooth has
reshaped our understanding of Alaska's ancient people, their genetic
background and their diets.
The tooth is only the third known remnant of a population of early
migrants known as Ancient Beringians. Combined with previous University
of Alaska Fairbanks research, the find indicates that Ancient Beringians
remained in Alaska for thousands of years after first migrating across
the Bering Land Bridge that connected eastern Asia and Alaska.
Investigation of the tooth, conducted by researchers at UAF and the
National Park Service in Alaska, was part of a larger paper published
Nov. 8 in the journal Science. That research included genetic
analysis of 15 diverse bone samples from sites across North and South
America, revealing a broad picture of how the Americas were populated by
its earliest peoples.
The Alaska tooth had been largely forgotten since it was excavated in
1949 by Danish archaeologists from the Trail Creek Caves site on
Alaska's Seward Peninsula. For almost 70 years it remained in storage in
Copenhagen, Denmark, until it was found in 2016 by Jeff Rasic, a
Fairbanks-based NPS archaeologist who was conducting new analyses of
this old collection.
Radiocarbon dating determined the tooth, which belonged to a
1½-year-old child, is by far the oldest human specimen in the North
American Arctic -- more than twice as old as the next oldest remains.
Genomic testing connected the tooth to the Ancient Beringian lineage.
The first traces of that population were discovered in 2013 by a team
led by UAF professor Ben Potter at a site in Alaska's Interior.
"This one small tooth is a treasure trove of information about
Alaska's early populations, not only their genetic affinities but also
their movements, interactions with other people and diet," said Rasic.
When looked at together, those two sites -- separated by about 400
miles and 2,500 years -- show that Ancient Beringians were present
across the vast expanse of Alaska for millennia.
"This new find confirms our predictions that Ancient Beringians are
directly linked with the cultural group known as the Denali Complex,
which was widespread in Alaska and the Yukon Territory from 12,500 to
about 6000 years ago," said Potter, who wasn't involved in the Science
paper.
Researchers worked with tribal officials from the Seward Peninsula village of Deering to coordinate efforts to study the tooth.
Analysis at UAF's Alaska Stable Isotope Facility also revealed
surprising details about the lives of the child and, by proxy, the
mother who fed the child. By studying chemical signatures preserved in
the tooth, ASIF Director Matthew Wooller was able to analyze their diet.
"The child's food sources were entirely terrestrial, a sharp contrast
with other sites that indicate inclusion of anadromous fish and marine
resources." said Wooller, who also works at UAF's College of Fisheries
and Ocean Science, and Water and Environmental Research Center.
That land-based diet is a surprise -- during the time the child lived
on the Seward Peninsula, sea levels had risen to nearly modern levels.
Those rising waters had cut off the Bering Land Bridge and surrounded
most of the peninsula, making marine resources accessible.
Further isotope results and modeling, which were conducted by Rasic,
Wooller and Clement Bataille from the University of Ottawa, also
determined the family resided in the region surrounding the caves, and
were not migrants from elsewhere in Alaska or Siberia.
"The combination of isotope signatures found in the tooth is pretty
specific to the interior Seward Peninsula, making a local origin for the
family very probable," Bataille said.
