Millet: The missing link in prehistoric humans' transition from hunter-gatherer to farmer

New research shows a cereal familiar today as birdseed was carried across Eurasia by ancient shepherds and herders laying the foundation, in combination with the new crops they encountered, of 'multi-crop' agriculture and the rise of settled societies. Archaeologists say 'forgotten' millet has a role to play in modern crop diversity and today's food security debate.

The domestication of the small-seeded cereal millet in North China around 10,000 years ago created the perfect crop to bridge the gap between nomadic hunter-gathering and organised agriculture in Neolithic Eurasia, and may offer solutions to modern food security, according to new research.

Now a forgotten crop in the West, this hardy grain - familiar in the west today as birdseed - was ideal for ancient shepherds and herders, who carried it right across Eurasia, where it was mixed with crops such as wheat and barley. This gave rise to 'multi-cropping', which in turn sowed the seeds of complex urban societies, say archaeologists.

A team from the UK, USA and China has traced the spread of the domesticated grain from North China and Inner Mongolia into Europe through a "hilly corridor" along the foothills of Eurasia. Millet favours uphill locations, doesn't require much water, and has a short growing season: it can be harvested 45 days after planting, compared with 100 days for rice, allowing a very mobile form of cultivation.

Nomadic tribes were able to combine growing crops of millet with hunting and foraging as they travelled across the continent between 2500 and 1600 BC. Millet was eventually mixed with other crops in emerging populations to create 'multi-crop' diversity, which extended growing seasons and provided our ancient ancestors with food security.

The need to manage different crops in different locations, and the water resources required, depended upon elaborate social contracts and the rise of more settled, stratified communities and eventually complex 'urban' human societies.

Researchers say we need to learn from the earliest farmers when thinking about feeding today's populations, and millet may have a role to play in protecting against modern crop failure and famine.

"Today millet is in decline and attracts relatively little scientific attention, but it was once among the most expansive cereals in geographical terms. We have been able to follow millet moving in deep history, from where it originated in China and spread across Europe and India," said Professor Martin Jones from the University of Cambridge's Department of Archaeology and Anthropology, who is presenting the research findings today at the Shanghai Archaeological Forum.

"These findings have transformed our understanding of early agriculture and society. It has previously been assumed that early agriculture was focused in river valleys where there is plentiful access to water. However, millet remains show that the first agriculture was instead centred higher up on the foothills - allowing this first pathway for 'exotic' eastern grains to be carried west."

The researchers carried out radiocarbon dating and isotope analysis on charred millet grains recovered from archaeological sites across China and Inner Mongolia, as well as genetic analysis of modern millet varieties, to reveal the process of domestication that occurred over thousands of years in northern China and produced the ancestor of all broomcorn millet worldwide.

"We can see that millet in northern China was one of the earliest centres of crop domestication, occurring over the same timescale as rice domestication in south China and barley and wheat in west China," explained Jones.

"Domestication is hugely significant in the development of early agriculture - humans select plants with seeds that don't fall off naturally and can be harvested, so over several thousand years this creates plants that are dependent on farmers to reproduce," he said.

"This also means that the genetic make-up of these crops changes in response to changes in their environment - in the case of millet, we can see that certain genes were 'switched off' as they were taken by farmers far from their place of origin."

As the network of farmers, shepherds and herders crystallised across the Eurasian corridor, they shared crops and cultivation techniques with other farmers, and this, Jones explains, is where the crucial idea of 'multi-cropping' emerged.

"The first pioneer farmers wanted to farm upstream in order to have more control over their water source and be less dependent on seasonal weather variations or potential neighbours upstream," he said. "But when 'exotic' crops appear in addition to the staple crop of the region, then you start to get different crops growing in different areas and at different times of year. This is a huge advantage in terms of shoring up communities against possible crop failures and extending the growing season to produce more food or even surplus.

"However, it also introduces a more pressing need for cooperation, and the beginnings of a stratified society. With some people growing crops upstream and some farming downstream, you need a system of water management, and you can't have water management and seasonal crop rotation without an elaborate social contract."

Towards the end of the second and first millennia BC larger human settlements, underpinned by multi-crop agriculture, began to develop. The earliest examples of text, such as the Sumerian clay tablets from Mesopotamia, and oracle bones from China, allude to multi-crop agriculture and seasonal rotation.

But the significance of millet is not just in transforming our understanding of our prehistoric past. Jones believes that millet and other small-seeded crops may have an important role to play in ensuring future food security.

"The focus for looking at food security today is on the high-yield crops, rice, maize and wheat, which fuel 50% of the human food chain. However, these are only three of 50 types of cereal, the majority of which are small-grained cereals or "millets". It may be time to consider whether millets have a role to play in a diverse response to crop failure and famine," said Jones.

"We need to understand more about millet and how it may be part of the solution to global food security - we may have a lot still to learn from our Neolithic predecessors."

Archaeologists discover location of historic battle fought by Caesar on Dutch soil

This is an overview of human skeletal remains from the Late Iron Age, dredged up in Kessel.
CREDIT
Vrije Universiteit Amsterdam

At a press conference held on Friday Dec. 11, 2015 in the Allard Pierson Museum in Amsterdam, archaeologist Nico Roymans from the Vrije Universiteit Amsterdam announced a discovery that is truly unique for Dutch archaeology: the location where the Roman general and statesman Julius Caesar massacred two Germanic tribes in the year 55 BC. The location of this battle, which Caesar wrote about in detail in Book IV of his De Bello Gallico, was unknown to date. It is the earliest known battle on Dutch soil. The conclusions are based on a combination of historical, archaeological, and geochemical data.

Skeletal remains, swords and spearheads

It is the first time that the presence of Caesar and his troops in Dutch territory has been explicitly proven. The finds from this battle include large numbers of skeletal remains, swords, spearheads, and a helmet. The two Germanic tribes, the Tencteri and the Usipetes, originated in the area east of the Rhine and had explicitly appealed to Caesar for asylum. Caesar rejected this request for asylum and ordered his troops to destroy the tribes by violent means. Nowadays, we would label such action genocide.

During the press conference, Roymans described in detail the discoveries made in Kessel (North Brabant) and their historical significance. He also showed weapons and skeletal remains from this battle.

Archaeologists unearth new evidence of Roman, medieval Leicester

Archaeologists from University of Leicester Archaeological Services (ULAS) have unearthed new evidence of Roman and medieval Leicester after recently completing the excavation of two areas at the former Southgates Bus Depot, on the corner of Southgates and Peacock Lane in the centre of Leicester.

Archaeologists, led by John Thomas and Mathew Morris of ULAS, have been investigating a series of medieval and post-medieval backyards dating from the 12th century through to the 16th century. These are likely to be associated with densely packed houses and shops which would have once fronted onto the important medieval street of Southgates.

Evidence recorded includes stone-lined pits (possibly storage pits or cisterns), rubbish pits, latrines, wells, boundary walls and a possible late 15th or 16th century cellar. Such activity, and the evidence carefully collected and recorded from it, will give important new insights into the lifestyles and industry of the people living along one of Leicester's principle medieval streets.

John Thomas said: "Having the chance to excavate in this part of Leicester is fantastic. Because of the historic nature of the modern city centre, archaeologists rarely get the opportunity to explore this part of the city. These excavations will provide important new insights into the character of the settlement and the inhabitants living in the southern half of the Roman and medieval town."

The project is funded by property developer Viridis and the University team has been working closely with them and their contractors WinVic to complete the archaeological investigation before construction of new student apartments begins.

The site lies at the heart of Leicester's historic core, close to significant Roman and medieval sites such as the Roman forum and the Jewry Wall Roman public baths as well as the site of Grey Friars, the medieval Franciscan friary where the remains of King Richard III (d.1485) were discovered by University archaeologists in 2012.

Once the medieval archaeology was painstakingly recorded and removed, evidence of Leicester's Roman past was slowly revealed. The junction of two Roman streets has been identified. These have thick, cambered gravel surfaces with drainage gullies dug to either side. A number of large stone and timber buildings, and boundary walls, dating from the 2nd century through to the 4th century have been identified running along the sides of the streets.

In some areas the Roman archaeology has been badly disturbed by later activity but elsewhere Roman remains are very well preserved with intact floors and rare fragments of wall still surviving above floor level. The broken remains of a mosaic pavement has been found in one building, whilst pieces of painted wall plaster still survived on the walls in another.

This evidence will allow the archaeologists to reconstruct what these buildings might have looked like. A wide array of artefacts have been recovered during the excavation, including coins, fine table ware, a copper spoon, game counters, a number of bone hair pins and other pieces of jewellery. This suggests that Roman activity in the area was predominately domestic in nature with some industrial activity going on in the vicinity in the later Roman period.

Mathew Morris added: "This part of Roman Leicester is very poorly understood because there has been little previous archaeological investigation in the vicinity. One of the Roman streets found on the site has never been seen before in Leicester and isn't on any of our plans of the Roman city. This is a significant find and raises exciting new questions about the layout of the early Roman town and how it evolved through the Roman period. It also means that the excavations are exploring three different insulae or blocks within the Roman street system. So far, there appears to be contrasting types of occupation in the different areas and this will give terrific new insights into life in Leicester during the Roman period."

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Impression of King Hezekiah’s Royal Seal Discovered in Ophel Excavations South of Temple Mount in Jerusalem

The Ophel excavations at the foot of the southern wall of the Temple Mount, conducted by the Hebrew University of Jerusalem’s Institute of Archaeology under the direction of Dr. Eilat Mazar, have unearthed an impression of the royal seal of King Hezekiah (727–698 BCE).

A seal impression of King Hezekiah unearthed in the Ophel excavations at the foot of the southern wall of the Temple Mount, conducted by the Hebrew University of Jerusalem’s Institute of Archaeology under the direction of Dr. Eilat Mazar.

(Courtesy of Dr. Eilat Mazar; Photo by Ouria Tadmor)

Measuring 9.7 X 8.6 mm, the oval impression was imprinted on a 3 mm thick soft bulla (piece of inscribed clay) measuring 13 X 12 mm. Around the impression is the depression left by the frame of the ring in which the seal was set.

The impression bears an inscription in ancient Hebrew script:

“לחזקיהו [בן] אחז מלך יהדה”
“Belonging to Hezekiah [son of] Ahaz king of Judah”

and a two-winged sun, with wings turned downward, flanked by two ankh symbols symbolizing life.

The bulla originally sealed a document written on a papyrus rolled and tied with thin cords, which left their mark on the reverse of the bulla. This bulla came to light, together with many pottery sherds and other finds such as figurines and seals, in Area A of the excavations (2009 season), supervised by Hagai Cohen-Klonymus.

The bulla was discovered in a refuse dump dated to the time of King Hezekiah or shortly after, and originated in the Royal Building that stood next to it and appears to have been used to store foodstuffs. This building, one of a series of structures that also included a gatehouse and towers, was constructed in the second half of the 10th century BCE (the time of King Solomon) as part of the fortifications of the Ophel — the new governmental quarter that was built in the area that connects the City of David with the Temple Mount.

The bulla was found together with 33 additional bullae imprinted from other seals, some bearing Hebrew names, their reverse showing marks of coarse fabric and thick cords that probably sealed sacks containing foodstuffs.

The Ophel excavations at the foot of the southern wall of the Temple Mount in Jerusalem, conducted by the Hebrew University of Jerusalem’s Institute of Archaeology under the direction of Dr. Eilat Mazar.

Dr. Eilat Mazar said: “Although seal impressions bearing King Hezekiah’s name have already been known from the antiquities market since the middle of the 1990s, some with a winged scarab (dung beetle) symbol and others with a winged sun, this is the first time that a seal impression of an Israelite or Judean king has ever come to light in a scientific archaeological excavation.”

A third-generation archaeologist working at the Hebrew University’s Institute of Archaeology, Dr. Mazar directs excavations on the City of David’s summit and in the Ophel to the south of the Temple Mount’s southern wall. Among her many archaeological finds over the years, in 2013 she revealed to the world an ancient golden treasure discovered at the Ophel (see http://new.huji.ac.il/en/article/18251).


The renewed Ophel excavations (2009-2013), and the processing of the finds as well as the preservation and preparation of the excavated area for tourists by the Israel Antiquities Authority were made possible through funding provided by Daniel Mintz and Meredith Berkman (New York).The excavation site is situated within the Ophel Archaeological Park, which is part of the National Park Around the Walls of Jerusalem under the auspices of the Israel Nature and Parks Authority.

The seal impression was found during the wet-sifting of earth layers from the excavation in the Emek-Zurim wet-sifting facility, directed by Dr. Gabriel Barkai and Zachi Dvira, under the auspices of the Nature and Parks Authority and the Ir David Foundation. The bulla was discovered by Efrat Greenwald, a member of the Ophel expedition, who supervised the wet-sifting of the excavation material. Reut Ben-Aryeh, who prepared the Hebrew bullae from the Ophel excavations for publication, was the first to identify it as a seal impression of King Hezekiah. Students and alumni of Herbert W. Armstrong College from Edmond, Oklahoma participated in the excavation.

King Hezekiah is described favorably in the Bible (II Kings, Isaiah, II Chronicles) as well as in the chronicles of the Assyrian kings— Sargon II and his son Sennacherib—who ruled during his time. Hezekiah is depicted as both a resourceful and daring king, who centralized power in his hands. Although he was an Assyrian vassal, he successfully maintained the independent standing of the Judean Kingdom and its capital Jerusalem, which he enhanced economically, religiously, and diplomatically.

The Bible relates of Hezekiah that “there was none like him among all the kings of Judah after him, nor among those before him” (II Kings 18:5).

The symbols on the seal impression from the Ophel suggest that they were made late in his life, when both the Royal administrative authority and the King’s personal symbols changed from the winged scarab (dung beetle)—the symbol of power and rule that had been familiar throughout the Ancient Near East, to that of the winged sun—a motif that proclaimed God’s protection, which gave the regime its legitimacy and power, also widespread throughout the Ancient Near East and used by the Assyrian Kings.

This change most likely reflected both the Assyrian influence and Hezekiah’s desire to emphasize his political sovereignty, and Hezekiah’s own profound awareness of the powerful patronage given his reign by the God of Israel. While the changed Royal administrative symbol imprinted on the King’s jars used the motif of a sun with wings extended to the sides, Hezekiah’s personal changed symbol had a sun with sheltering wings turned down and a life-symbol at the end of each wing. This special addition of the symbol of life may support the assumption that the change on the King’s personal seal was made after Hezekiah had recovered from the life-threatening illness of shehin (II Kings 20:1-8), when the life-symbol became especially significant for him (ca. 704 BCE).

The discovery of King Hezekiah’s Royal Seal impression in the Ophel excavations vividly brings to life the Biblical narratives about King Hezekiah and the activity conducted during his lifetime in Jerusalem’s Royal Quarter.

The full research about King Hezekiah’s bulla is included in the first volume of the Ophel Excavations 2009–2013 Final Reports, published today with the support of the David Berg Foundation.

Seeds Discovered in Excavations Indicate Prehistoric Man Living in the Southern Near East 10,000 Years Age

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A joint study by researchers of the Weizmann Institute and the Israel Antiquities Authority, which examined fava seeds exposed in archaeological excavations in recent years at Neolithic sites in the Galilee, sheds light on the nutritional habits of the people that lived in the area 10,000 years ago. Seeds found at the prehistoric sites show that the inhabitants’ diet at the time consisted mainly of fava beans, as well as lentils, various types of peas and chickpeas.

The study was conducted by archaeobotanist Valentina Caracuta, of the Weizmann Institute, together with Dr. Elisabetta Boaretto and Dr. Lior Regev, and in cooperation with archaeologists Dr. Kobi Vardi, Dr. Yitzhak Paz, Dr. Hamoudi Khalaily, Dr. Ianir Milevski and Dr. Omri Barzilai of the Israel Antiquities Authority.

The multitude of fava seeds found at the Neolithic sites excavated in the Galilee during the past few years indicates the preference placed on growing fava beans. The dating of the seeds, which was done at the Kimmel Center in the Weizmann Institute, indicated a range of dates between 9,890–10,160 YBP. These well-preserved seeds were found in excavations, inside storage pits (granaries) after they had been husked. The seeds’ dimensions are a uniform size–a datum showing they were methodically cultivated, and were harvested at the same period of time, when the legumes had ripened. According to the researchers, keeping the seeds in storage pits is also reflective of long-term agricultural planning, whereby the stored seeds were intended not only for food, but also to ensure future crops in the coming years.

The researchers added, “The identification of the places where plant species that are today an integral part of our diet were first domesticated is of great significance to research. Despite the importance of cereals in nutrition that continues to this day, it seems that in the region we examined (west of the Jordan River), it was the legumes, full of flavor and protein, which were actually the first species to be domesticated. A phenomenon known as the agricultural revolution took place throughout the region at this time: different species of animals and plants were domesticated across the Levant, and it is now clear that the area that is today the Galilee was the main producer of legumes in prehistoric times. This is a process that lasted thousands of years, during which certain characteristics of wild species changed, and domesticated plant species were created. To this day, most of the chickpeas grown in the country are cultivated in the Galilee region”.

According to the archaeologists, the accurate dating of the fava seeds, utilizing advanced techniques, led to the conclusion that they found the world’s oldest domesticated fava seeds, dating to 10,125–10,200 YBP.

New clues emerge about the earliest known Americans

Stone tools, cooked animal and plant remains and fire pits found at the Monte Verde site in southern Chile provide greater interdisciplinary evidence that the earliest known Americans--a nomadic people adapted to a cold, ice-age environment--were established deep in South America more than 15,000 years ago. The research, led by Tom Dillehay, Rebecca Webb Wilson University Distinguished Professor of Anthropology, appears in the Nov. 18 issue of PLOS ONE. 

A very small faceted basalt wedge. Basalt is a local material. This tool, also found at MVI, was made 15,000-16,000 years ago. It would have been used for woodworking.

CREDIT

(Courtesy Tom Dillehay)

In 2013, at the request of Chile's National Council of Monuments, Dillehay and an international team of archaeologists, geologists and botanists performed an archaeological and geological survey of Monte Verde to better define the depth and breadth of the site, which is protected by the Chilean government. 

It's familiar ground for Dillehay, who has worked there since 1977, and it's there that Dillehay found evidence that fundamentally contributed to a new understanding of how and when humans first arrived in the Americas. 

Until about 40 years ago, the prevailing understanding was that the Americas first began to be populated 13,000 years ago by big-game hunters from Asia who used a distinctive type of fluted stone projectile point called Clovis points. Dillehay's work at Monte Verde, however, has yielded a wide variety of scientific evidence of a small human settlement using a different stone tool technology that predated the Clovis people by about 1,500 years at a site called MVII. He also uncovered possible, though not conclusive, evidence of a much earlier human presence at a nearby site called MVI. Subsequent excavations at sites in both North and South America have also yielded evidence supporting this earlier human migration through the Americas. 

On this visit, Dillehay's team explored key areas around MVI and MVII. Though it was not intended to be a comprehensive reexamination of the site, their findings did yield new insights. "We began to find what appeared to be small features--little heating pits, cooking pits associated with burned and unburned bone, and some stone tools scattered very widely across an area about 500 meters long by about 30 or 40 meters wide," said Dillehay. 

The stone tools discovered by the team were similar to what Dillehay had previously found at Monte Verde. Many were simple unifacial tools--meaning they were worked on only one side of the stone, to create a sharp edge--though some of the younger tools and projectile points indicate bifacial technologies. "One of the curious things about it that is that unlike what we found before, a significant percentage, about 34 percent, were from non-local materials. Most of them probably come from the coast but some of them probably come from the Andes and maybe even the other side of the Andes," said Dillehay. Prior research had revealed evidence of Andean plants in the area, providing further support for a highly mobile population. 

Stones, bones, plants and fires

The team recovered a total of 39 stone objects and 12 small fire pits associated with bones and some edible plant remains, including nuts and grasses. The bones tended to be small fragments, broken and scorched, indicating that the animals had been cooked. They often came from very large animals, like prehistoric llamas or mastodons, as well as smaller creatures like prehistoric deer and horses. The Monte Verde site was unlikely to have been able to support the kind of vegetation that those animals needed to eat, so they were likely killed and butchered elsewhere. The objects were radiocarbon dated and most were found to range in age from more than 14,000 to almost 19,000 years old. 

The wide scattering suggests that the people who created these features were nomadic hunter-gatherers who might have camped for only a night or two before moving on. "Where they're going, we don't know, and where they're coming from, we don't know, but this would have been a passageway from the coast to the foothills of the Andes," Dillehay said. Dillehay believes that they may have come through Monte Verde because the terrain was more walkable than the surrounding bogs and wetlands, and because it provided access to stone to make tools.

Rain, ice, soil and ash

A key goal during this visit was to better understand the geological and environmental context of the site. At the end of the last ice age, Monte Verde was a sandur plain--a runoff area situated about six kilometers away from a glacier, crisscrossed by a network of shallow streams and brooks fed by rain washing off the glacier, as well as melting snow. It was also a time marked by volcanic activity and a gradually warming climate, as the last glaciers began to retreat.

"It appears that these people were there in the summer months," Dillehay said. "Each one of these [burned] features and the bones and stones associated with them is embedded in thin, oxidized tephra"--a type of geological layer formed by airborne ash particles from nearby volcanoes that only form in rainy, warmer temperatures. But though the glaciers had begun to retreat by 19,000 to 17,000 years ago, it was still an extremely challenging environment, Dillehay said. "We're looking at people living in some really cold, harsh areas, even in the summer months." Only later, around 15,000 years ago, did the climate warm enough to support the kind of longer-term settlement found at MVII. 

New questions

Put together, these findings support the paradigm shift toward an earlier peopling of the Americas, although questions inevitably remain about how the hemisphere was settled. It also underscores the importance of long-term interdisciplinary research. "We now realize that the geology and the climate and the archaeology are much more complex than we ever calculated," said Dillehay.

'Fourth strand' of European ancestry originated with hunter-gatherers isolated by Ice Age

  

IMAGE: DNA WAS EXTRACTED FROM THE MOLAR TEETH OF THIS SKELETON, DATING FROM ALMOST 10,000 YEARS AGO AND FOUND IN THE KOTIAS KLDE ROCKSHELTER IN WESTERN GEORGIA.

CREDIT: EPPIE JONES

The first sequencing of ancient genomes extracted from human remains that date back to the Late Upper Palaeolithic period over 13,000 years ago has revealed a previously unknown "fourth strand" of ancient European ancestry. 

This new lineage stems from populations of hunter-gatherers that split from western hunter-gatherers shortly after the 'out of Africa' expansion some 45,000 years ago and went on to settle in the Caucasus region, where southern Russia meets Georgia today. 

Here these hunter-gatherers largely remained for millennia, becoming increasingly isolated as the Ice Age culminated in the last 'Glacial Maximum' some 25,000 years ago, which they weathered in the relative shelter of the Caucasus mountains until eventual thawing allowed movement and brought them into contact with other populations, likely from further east. 

This led to a genetic mixture that resulted in the Yamnaya culture: horse-borne Steppe herders that swept into Western Europe around 5,000 years ago, arguably heralding the start of the Bronze Age and bringing with them metallurgy and animal herding skills, along with the Caucasus hunter-gatherer strand of ancestral DNA - now present in almost all populations from the European continent. 

The research was conducted by an international team led by scientists from Cambridge University, Trinity College Dublin and University College Dublin. The findings are published today in the journal Nature Communications. 

"The question of where the Yamnaya come from has been something of a mystery up to now," said one of the lead senior authors Dr Andrea Manica, from Cambridge's Department of Zoology. 

"We can now answer that as we've found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation. This Caucasus pocket is the fourth major strand of ancient European ancestry, one that we were unaware of until now," he said 

Professor Daniel Bradley, leader of the Trinity team, said: "This is a major new piece in the human ancestry jigsaw, the influence of which is now present within almost all populations from the European continent and many beyond." 

Previously, ancient Eurasian genomes had revealed three ancestral populations that contributed to contemporary Europeans in varying degrees, says Manica. 

Following the 'out of Africa' expansion, some hunter-gatherer populations migrated north-west, eventually colonising much of Europe from Spain to Hungary, while other populations settled around the eastern Mediterranean and Levant, where they would develop agriculture around 10,000 years ago. These early farmers then expanded into and colonised Europe. 

Finally, at the start of the Bronze Age around 5,000 years ago, there was a wave of migration from central Eurasia into Western Europe - the Yamnaya. 

However, the sequencing of ancient DNA recovered from two separate burials in Western Georgia - one over 13,000 years old, the other almost 10,000 years old - has enabled scientists to reveal that the Yamnaya owed half their ancestry to previously unknown and genetically distinct hunter-gatherer sources: the fourth strand.

By reading the DNA, the researchers were able to show that the lineage of this fourth Caucasus hunter-gatherer strand diverged from the western hunter-gatherers just after the expansion of anatomically modern humans into Europe from Africa. 

The Caucasus hunter-gatherer genome showed a continued mixture with the ancestors of the early farmers in the Levant area, which Manica says makes sense given the relative proximity. This ends, however, around 25,000 years ago - just before the time of the last glacial maximum, or peak Ice Age. 

At this point, Caucasus hunter-gatherer populations shrink as the genes homogenise, a sign of breeding between those with increasingly similar DNA. This doesn't change for thousands of years as these populations remain in apparent isolation in the shelter of the mountains - possibly cut off from other major ancestral populations for as long as 15,000 years - until migrations began again as the Glacial Maximum recedes, and the Yamnaya culture ultimately emerges. 

"We knew that the Yamnaya had this big genetic component that we couldn't place, and we can now see it was this ancient lineage hiding in the Caucasus during the last Ice Age," said Manica. 

While the Caucasus hunter-gatherer ancestry would eventually be carried west by the Yamnaya, the researchers found it also had a significant influence further east. A similar population must have migrated into South Asia at some point, says Eppie Jones, a PhD student from Trinity College who is the first author of the paper. 

"India is a complete mix of Asian and European genetic components. The Caucasus hunter-gatherer ancestry is the best match we've found for the European genetic component found right across modern Indian populations," Jones said. Researchers say this strand of ancestry may have flowed into the region with the bringers of Indo-Aryan languages. 

The widespread nature of the Caucasus hunter-gatherer ancestry following its long isolation makes sense geographically, says Professor Ron Pinhasi, a lead senior author from University College Dublin. "The Caucasus region sits almost at a crossroads of the Eurasian landmass, with arguably the most sensible migration routes both west and east in the vicinity."

He added: "The sequencing of genomes from this key region will have a major impact on the fields of palaeogeneomics and human evolution in Eurasia, as it bridges a major geographic gap in our knowledge."

David Lordkipanidze, Director of the Georgian National Museum and co-author of the paper, said: "This is the first sequence from Georgia - I am sure soon we will get more palaeogenetic information from our rich collections of fossils."