There are over 50,000 people in North America who define themselves as Hutterites, though you probably have never met one. One of the main branches of the Anabaptists, Hutterites live in self-sustaining communities throughout the rural northwestern United States and Canada.

Like their sister branches, the Amish and the Mennonites, the history and culture of the Hutterites have long fascinated scholars. But there have been few forays into the genetics of this unique community — until now. In the October 21 issue of the European Journal of Human Genetics, geneticist Irene Pichler and an international team of experts set out to unravel the genetic history of the Hutterites.

The history of the Hutterites goes back over 500 years, to a stretch of land in northernmost Italy called Tyrol. It was here that a small group of people, led by local hatmaker Jakob Hutter, formed a religious community centered on absolute pacificism and communal living. The Hutterites, as they came to be known, were part of the Radical Reformation, which rejected the teachings of both the Roman Catholic Church and the more moderate Protestant movement.

Due in no small part to their adherence to pacificism, the Hutterites soon became victims of persecution and expulsion. They moved several times to new settlements in central and eastern Europe. Their numbers dwindled significantly. By 1755, only 67 Hutterites were living in Transylvania.

By 1874, the Hutterites had had enough, and over 1,200 departed Europe for the rich farmland of western North America. They settled in present-day South Dakota, setting up several colonies. Today they are living much as they were upon their arrival in both the United States and Canada.

The Hutterites’ distinct and well-documented history over the past several centuries could make for an equally unique genetic history. Would traces of their history be etched in their genes? This is exactly what Pichler and her team sought to find out.

Pichler’s team focused on two segments of the human genome: the mitochondrial DNA and the Y chromosome. Because mitochondrial DNA (mtDNA) is passed down along the mother’s line, and the Y chromosome is passed down along the father’s line, the team could use both to paint a detailed picture of the Hutterites’ genetic history. The research team also analyzed DNA from several Central European groups for comparison, as central Europe is the Hutterites’ ancestral home.

Pichler proposed that the same constant reductions in population size that continually plagued the Hutterites, must also show up in their DNA. And that is exactly what happened. Among all the Hutterite DNA samples analyzed, the authors found only 11 distinct types of mtDNA (called haplogroups), and only 10 distinct Y-chromosome haplogroups. In other words, the Hutterites’ ancestral maternal and paternal lines trace back to just 21 individuals. This is an extremely small number of founders, and is further evidence that the large drops in Hutterite population size over the centuries are found in their genes.

Pichler and her team further discovered that the haplogroups among the Hutterites are vastly different from those found among central Europeans. For example, 30 percent of Hutterites belonged to a single haplogroup called X2c1 — which is virtually absent in Europe. This shows that even while the Hutterites lived in Europe, their genetics were vastly different from their non-Hutterite neighbors.

Centuries of isolation from the rest of Europe, followed by their massive migration to a new continent and continued isolation, have clearly defined the Hutterite people. And this study has revealed the history and genetics of this community as one of the most unique in North America.

Photo courtesy of Wikimedia Commons.

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The Near East – a swath of land that encompasses the Arabian Peninsula, the Levant, and everywhere in between – has been populated by humans longer than anywhere else in the world save Africa. It is where agriculture was born and spread into Eurasia. It is where the ancient civilizations of Mesopotamia and Egypt evolved and flourished. And it is where a particular paternal haplogroup, J1e, arose about 10,000 years ago.

Paternal haplogroups define a person’s all-male ancestry (i.e. the origins of your father’s father’s father, etc.), and are passed down from father to son via the Y chromosome. Haplogroup J1e has long interested experts because it seems to have expanded and flourished in the harsh deserts of Arabia. Today it is quite common among Bedouin nomads from Saudi Arabia, United Arab Emirates, and Oman, as well as in men from Turkey, Ethiopia, and the Levant.

In 2008, scientists at Stanford University proposed that the presence of J1e throughout the Near East could be tied to the nomadic hunter-herders who have dotted the region for thousands of years. In the October 14 issue of the European Journal of Human Genetics, these same scientists – including 23andMe consultants Roy King and Peter Underhill and 23andMe scientist Brenna Henn – test this theory with a little help from the field of linguistics.

The authors analyzed the DNA of more than 500 men from nearly 40 locations throughout the Near East. While many of these men belonged to haplogroup J1e, there were small genetic variations within J1e based on exactly where these men lived. For example, J1e samples from Turkey were slightly different from those in Oman.

When the authors examined differences among the ancient peoples of the Near East, they discovered that the languages spoken in different parts of the region were quite distinct. Until the Arabic swept across the Near East more than 1,000 years ago, there were dozens of languages spoken in the region: Aramaic in Syria, Babylonian in Iraq, and Canaanite from Lebanon to Jordan. The majority of these tongues are now extinct, but all belong to the same Semitic language family, to which Hebrew and Arabic also belong.

The authors reasoned that the history of these ancient languages may be tied to that of the people who spoke them. The history of these ancient people could be deciphered further by examining their genetic ancestry via paternal haplogroup J1e.

The researchers’ combined analysis of the J1e types and the ancient Semitic languages revealed some startling results. The authors found that J1e arose in Anatolia (present-day Turkey), expanding southward toward Arabia 10,000 years ago.

Limited archaeological evidence supports such an expansion, when hunter-gatherer groups, using bow-and-arrow technology and with the help of domesticated dogs, headed south into the heart of the Near East. Soon after they began expanding, the hunter-gatherers took up herding, domesticating animals like cattle and goats.

The linguistic evidence lends additional support. The common ancestor of all Semitic languages, called proto-Semitic, originated about 7,500 years ago, just as J1e was expanding. More importantly, the spread of proto-Semitic coincides with the spread of hunter-herders across the Near East.

So what does all this mean? The expansion of haplogroup J1e is closely tied to the expansion of the Semitic languages. And they are both linked to the expansion of hunter-herders, who journeyed from Anatolia southward into Arabia thousands of years ago. We now know just a little bit more about the ancient history of this fascinating region.

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Through the millennia wave after wave of migrants – often in the form of invading armies – have descended upon the British Isles.

The first people to arrive after the Ice Age were hunter-gatherers who followed their prey north from southern Europe about 12,000 years ago. The Celts came from central Europe about 3,000 years ago. Then came the Romans, followed by the Anglo-Saxons, Vikings and finally the Normans in 1066 AD.

With each successive invasion, the previous people were either absorbed by the invaders, or retreated to the isolated corners of the Isles. Often called the “Celtic Fringe,” these regions have been studied as a window into the ancient history of the British Isles. Some scholars even propose that the present-day people of the fringe could be direct descendants of the earliest humans to arrive on the Isles after the Ice Age.

But despite exhaustive research into the history and genetics of the Celtic Fringe, its prehistory remains mysterious, forcing scientists to think outside the box. In the September 30 issue of the Proceedings of the Royal Society B: Biological Sciences, biologist Jeremy Searle and his research team did just that, devising an unconventional method to study the prehistoric peopling of the British Isles.

They could have examined the DNA of the Celts themselves. But that’s already been tried, so Searle and his colleagues turned their research underfoot.

Earlier analysis found similar genetic patterns in populations of both common shrews and humans inhabiting the Celtic Fringe. Using those results as a benchmark, Searle and his team expanded the genetic analysis to the pygmy shrew as well as two species of voles.

Searle reasoned that if these shrews and voles had similar immigration patterns to early humans, perhaps those patterns would show up in their DNA. Specifically, he believes that “this study can help us understand why humans in the British Isles form a Celtic Fringe.”

Interestingly, Searle and his colleagues’ analysis revealed a division in DNA types for the shrews and voles similar to that separating the people of the Celtic Fringe and the rest of the British population. Further analysis revealed that the DNA types for the mammals living in the Celtic Fringe were quite old. So old, in fact, that Searle and his team propose that the arrival of these mammals traces all the way back to the post-Ice Age arrival of humans 12,000 years ago.

If the mammals living in the Celtic Fringe date back 12,000 years, the people living there could as well.

There is one problem with this hypothesis. The Celts themselves only arrived from mainland Europe 3,000 years ago, not 12,000 years ago. Conventional wisdom states that the Celtic Fringe only evolved after the Celts were pushed back following the invasion of the Romans and Anglo-Saxons.

How does Searle explain this discrepancy? He and his team argue that the Celtic Fringe is not actually Celtic in origin. Rather, its presence predates the arrival of the Celts and their arrival only ‘reinforced’ a pre-existing division that was already there.

In that case, it would have been the Celts themselves whose arrival pushed earlier inhabitants to the isolated corners of the British Isles. Subsequent migrations would have pushed the Celts into these same corners, which is why the language and culture of these regions are inherently Celtic. And that would also explain why the languages, culture, and history of the pre-Celtic people of Britain have mostly been lost to time.

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For as long as humans have lived in complex communities, cities and civilizations, they have divided and classified their societies. Those divisions have been based on age, gender, appearance or – in many cases – occupation. In many traditional societies artisans would share the same social status; as would soldiers, priests and workers in any number of other occupations.

In antiquity, the status of a family rarely changed. If you were a farmer, your sons would be farmers, and so on. While today social status barriers are crumbling in many societies, in others they remain largely unchanged.

India’s complex social stratification, known as the caste system, has been one of the traditional cornerstones of society. Though urban Indians are shedding the caste labels of their parents and grandparents, many rural Indians – who make up 72% of the entire population – hold steadfast to the system. In small villages and towns, the Brahmin caste – consisting of scholars and priests – is still revered as one of the highest social strata. And members of the Dalit caste – formerly known as “Untouchables” – are still viewed as unclean and remain separated from others.

The rigidity of the system still present in rural India has made many wonder exactly how long castes have existed. Historical records are unclear, as early Hindu scriptures like the Bhagavad Gita are somewhat ambiguous when it comes to the topic. Some historians even propose that the caste system as we know it today is largely a construct of the English Colonial Era, arguing that the development of such a system could have been deemed necessary to instill order.

Genetic analysis has also proven inconclusive, as analysis of small segments of the human genome has yielded different results. But a new study by geneticist David Reich and colleagues, published in the September 24 issue of Nature, takes a new approach to understanding the genetic history of India.

The core difference between Reich’s genetic analysis and previous studies is in the sheer amount of genetic material analyzed. Reich’s team examined more than 550,000 points across all segments of the human genome. In doing so, they hoped to obtain a more complete picture of Indian genetic history.

The research team analyzed the DNA of 132 individuals from India and neighboring regions, dividing them into 25 distinct groups based on geography, caste and language. They calculated how genetically ‘closed’ each of these groups were. In the caste system it is rare to marry someone from another class, making caste societies very closed, or ‘endogamous.’ If this endogamy continues over many generations, it will leave a behind a genetic signature for scientists to discover.

Reich and his team found such a signature, indicating a long history of endogamy in several of the groups. In fact, the research team calculated that the DNA of six of the groups can be traced back to just a few individuals who lived anywhere from 30 to more than 100 generations ago. Assuming a generation time of 25 years, that establishes the existence of the caste system in the range of 750 to more than 2,500 years ago — long before the British colonial era.

In a second analysis, Reich and his team examined how ancient migrations could have influenced the formation of castes. First the researchers divided the Indian groups into language families: Indo-European and Dravidian. Dravidian tongues, like Tamil and Malayalam, are mainly spoken in southern India and are believed to be a remnant of languages spoken by some of the earliest inhabitants of the region. Indo-European languages, like Punjabi and Urdu, are more common in the north. They are believed to have arrived with a migration of farmers from southwestern Asia or the Near East about 9,000 years ago.

Reich and his colleagues then compared the genetics of each of the Dravidian and Indo-European groups to a sample of European DNA. The team reasoned that, if Indo-European groups were really descended from the farmers, they would show more genetic similarity to the Europeans than the Dravidians.

Not surprisingly, the authors’ hypothesis held true. The Indo-European speakers, like the Kashmiri Pandit and Vaish, were more genetically similar to Europeans. And because the majority of the upper castes speak Indo-European languages, while the lower ones tend to be Dravidian speakers, there could be a relationship between the arrival of Indo-European people and the formation of caste structure. Further evidence that an ancient caste system has permeated through India for thousands of years.

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Take a look at the second installment of 23andMe’s Human Prehistory 101 series.  23andMe’s creative team (led by chief illustrator Ariana Killoran) recently released “Out of (Eastern) Africa.”  With this new installment, we pick up where the previous video left off, when humans were starting to take their first tentative steps beyond the shores of Africa and into the unknown.

We begin this second episode around 60,000 years ago, when early human groups were exploring Africa for food and other resources. Just a few thousand years later, a few people journeyed even farther, heading east into the Arabian Peninsula, Asia, Europe and beyond. The common theme here? Things were changing for our human ancestors, who had previously stayed relatively confined to their homeland but now they were on the move. Around the time they first set foot in Asia, humans in Africa began creating sophisticated stone tools and art the likes of which had never been seen before.

As humans ventured into uncharted territory, they may have encountered other species who bore some resemblance to themselves.  In Asia, they may have run into Homo erectus, a distant relative that had journeyed into Asia from Africa almost 2 million years earlier.  In Europe humans likely came across the Neanderthals, another related species that had been braving the cold northern latitudes of Europe and western Asia for hundreds of thousands of years.

Our story continues as we see where various human populations settled over the next several thousand years, and gives us a peek at the difficulties that awaited them as the harsh Ice Age approached. Subsequent episodes will document how our human ancestors survived the harsh Ice Age conditions and how the innovation of agriculture and development of language laid the groundwork for the genetic diversity we see today.  Enjoy this latest installment and stay tuned for future episodes of Human Prehistory 101!

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About 10,000 years ago, the prehistoric hunter-gatherers of Europe began meeting some new neighbors.

These farmers spread gradually at first, expanding from the Near East through Anatolia and the Balkans. Then agriculture exploded, reaching present-day Britain within a few thousand years. The farmers settled into houses, which soon evolved into villages, towns and eventually cities.

The archaeological record tells us that much. But what it doesn’t reveal is how agriculture spread. Did it spread like a fad, as hunter-gatherer groups saw what their neighbors were doing and imitated their ways? Or was it more of an invasion, with subsequent generations of farmers advancing across the continent and overwhelming indigenous hunter-gatherer populations as they went?

Some genetic studies suggest the former. But in the September 3 issue of Science, the first study to directly compare ancient DNA (aDNA) from prehistoric burials of hunter-gatherers to that their agricultural neighbors suggests migrants spread farming through Europe.

The research team, led by Barbara Bramanti of Mainz University, sequenced the mitochondrial DNA (mtDNA) of just under 50 individuals unearthed from various prehistoric burial sites across central and eastern Europe. Half the individuals came from hunter-gatherer societies, and the other half from communities based around farming. As a comparison, they also sequenced the mtDNA of nearly 500 modern Europeans from the same parts of Europe.

The authors’ first task was to compare the hunter-gatherer mtDNA to that of the farmers. Upon doing so, they found both groups to be so different from each other that there is no way the two could be closely related. There was absolutely no overlap in the kinds of mtDNA lineages – known as haplogroups – between the hunter-gatherers and the farmers. This stark difference suggests the earliest farmers were not related to the hunter-gatherers, and most likely came to the region by migration.

And how do these two groups compare to the modern-day Europeans? The hunter-gatherers had little in common with modern people. Haplogroup U, the most common lineage among the hunter-gatherers, is one of the least common haplogroups among modern Europeans.

But the authors also found little to connect the farmers to modern Europeans. Other studies have pointed to a substantial genetic component from the Near East among Europeans, but the authors found many genetic differences between the two groups.

Based on these results, the authors have proposed an alternative theory. The unexplained component to the genetic make-up of modern Europeans may be explained by later migrations that post-date the skeletal remains examined here. It could have been a later expansion of farmers from the Near East, or perhaps an influx of hunter-gatherers from the west. The exact details remain unclear, but the authors are confident that, with additional DNA analysis, they can hope to unravel the increasingly complex story of the peopling of Europe.

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There are many examples around the world of two distinct ethnic groups living side by side.

Sometimes these groups co-exist peacefully. Other times they do not.

Often two groups’ differences – along with circumstantial factors – lead to tension between them and sometimes violence. The Hutus and Tutsis of Rwanda, the Sunnis and Shiites of Iraq, and the Croats and Serbs of former Yugoslavia all illustrate how cultural distinctions – like language and religion – can contribute to tensions and conflict around the globe.

But do these cultural and ethnic distinctions translate to biological distinctions as well? Exactly how biologically distinct are two ethnic groups living side by side? Anthropologist Evelyn Heyer and an international team of researchers set out to answer these and many other questions by studying the adjacent – and culturally very different – Tajik and Turkic speakers along the Silk Road of Central Asia. Their results are published in this week’s BMC Genetics.

The authors focused on the Tajik and Turkic speakers because those groups offered a unique perspective on how two groups living in such close proximity can be so different from each other.

The Turks are largely nomadic herders. They speak Indo-Iranian languages like Azerbaijani, Turkish, and Altay. Their society is organized into clans, or “descent groups,” whose membership is passed down from father to children.

The Tajiks are, conversely, agriculturalists. They speak various dialects of the the Tajik, or Tajik Persian, language that may have arrived with Muslim invaders 1,000 years ago. Their society is largely patrilocal – meaning that when couples marry they put up residence near the husband’s family; and first cousin marriages are encouraged.

The two societies are supposedly closed, and members of both groups are said to rarely leave their clan or village. This cultural isolation made them perfect candidates for Heyer and her team to study.

So the researchers collected both maternally inherited mitochondrial DNA and paternally inherited Y chromosome DNA from more than 1,000 individuals spanning 24 Turkic and Tajik populations.

What they found was that these two ethnic groups weren’t so different after all.

Genetically, the Tajiks and the Turks were virtually indistinguishable. The authors found the overall level of genetic diversity between the two groups to be less than 1% overall — so small that there was a greater amount of diversity within each group than between the two.

Their analysis also shed some light on the origins of these these two ethnic groups. The modern-day people of Central Asia maintain their own origin stories that are unique to their particular group. In part, it is these unique origin stories that distinguish them from one another. But Heyer’s analysis proves that these groups actually share the same roots; they are simply a hodgepodge of the clans, tribes, and villages that have called Central Asia their home for thousands of years. Over many generations they banded together to form larger groups until they consolidated into just two major divisions: the Tajiks and the Turks.

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Ten millennia ago, there were about six million people on Earth. Today, there are six billion.

This thousandfold increase in the global population is often thought to be linked to the invention of farming and the domestication of animals about 13,000 years ago in the Near East. Growing crops and raising live animals requires a larger work force than hunting or gathering, so as agriculture took hold, families grew in size. These families grew into villages, villages grew into towns and cities, which eventually consolidated into the vast civilizations in ancient Mesopotamia, Egypt, and elsewhere.

Was this surge during the early days of agriculture the ONLY time in the history of our species that the worldwide population size of humans experienced a substantial boost? The traditional answer was yes. Early human hunter-gatherer populations were relatively stable, their overall size not changing much from generation to generation. Stone-age humans had a limited number of gazelles to hunt, berries to pick and eggs to snatch. Those ecological limitations suggest that pre-agricultural communities would have grown only modestly, even when the hunting was good.

But a new DNA analysis published in the July 29 issue of PLoS One suggests that the world’s human population grew dramatically even long before the development of farming.

Earlier analyses of mitochondrial DNA (mtDNA) have suggested that there were bursts of population growth much further back in time, but those studies have been unable to pinpoint a specific time span.

Geneticist Michael Hammer and his colleagues looked at nuclear DNA from four African populations: the San hunter-gatherers of the Kalahari Desert, the Biaka Pygmies of the Central African Republic, the Mandenka of Senegal and the Yorubans of Nigeria. Nuclear DNA is useful here because it is more sensitive to population size changes than mtDNA.

The authors found genetic evidence for a surge in human population size about 40,000 to 50,000 years ago. This period, just after humans first set foot outside Africa, is of great interest to archaeologists because it coincides with a dramatic increase in the sophistication of human behavior. People began crafting tools from bone, burying their dead and fashioning clothing to keep themselves warm in cool climates. They developed complex hunting techniques, and created great works of art in the form of cave paintings and jewelery.

The archaeological record also shows that during this time, humans began hunting more dangerous prey and more easily exploiting small game like rabbits and birds. They traveled farther than they had before, perhaps due to the growth of long-distance trade routes – the first of their kind. Jared Diamond, author of The Third Chimpanzee, calls this period “The Great Leap Forward,” when humans burst forth culturally – finally separating themselves from their evolutionary cousins.

The exact cause for these changes in human behavior may never be known. Some believe a simple genetic mutation or that the evolution of language could have sparked such a dramatic change. But what we do know now, thanks to this new genetic research, is that like the invention of agriculture this explosion of innovation was accompanied by population growth.

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In 1974, scientists digging in the dry lake bed of Lake Mungo in southeastern Australia uncovered the skeleton of a man preserved in the deep layers of sand and clay. Dating techniques eventually revealed that this individual died about 40,000 years ago.

Scientists and the popular press dubbed the individual “Mungo Man.” Why did he make such a splash?  Not only because he was – and remains – one of the oldest and most complete skeletons of the earliest Australians, but because his appearance shattered the previously held notion that humans had first set foot in Australia less than 10,000 years ago. It was so far from where humans arose in Africa, and so remote.  So of course humans arrived there so much later than everywhere else, many experts reasoned. With the discovery of Mungo Man, this idea lost support, and scientists now concede that Australia was settled much earlier than many other parts of the world, including the Americas and parts of Europe.

While this discovery initially answered many questions regarding the peopling of Australia, it left many more unanswered — especially how people could have reached an island continent so soon after humans first expanded beyond Africa about 60,000 years ago.

The thinking is that after leaving Africa, one or more groups of humans journeyed from their homeland in East Africa into Arabia via the Red Sea. Over the next several thousand years, their descendants continued along the coasts of Arabia and India, eventually heading south into present-day Indonesia and finally to Australia, which was joined with the island of New Guinea at the time.

There has been some archaeological and genetic evidence of such a migration, but most of it has been indirect or circumstantial. Some scientists remain unconvinced because researchers have not been able to show a direct link between modern Australian Aborigines and modern people living along the coastal route from Africa. But now, in a new study led by the Anthropological Survey of India, geneticists believe they’ve found the first concrete evidence of such a link. Their results are reported in the July 21 issue of BMC Evolutionary Biology.

The team, led by Satish Kumar, reasoned that if the hypothesis of an ancient migration along the Indian Ocean coast toward Australia was accurate, there would be evidence in the DNA of modern people living along that path. So they compared the DNA of modern Australian Aborigines to that of tribes from India, such as the Baiga of central India and the Birhor of eastern India. These groups are often called “relic populations” because they are believed to share many cultural, linguistic, physical and genetic features with the region’s ancient inhabitants.

Experts have long noticed that the Baiga, Birhor and other relic populations share physical similarities with native Australians. Kumar and his team reasoned that there could be DNA similarities too.

Kumar led the extraction and analysis of mitochondrial DNA (mtDNA) from nearly 1,000 individuals from Indian relic populations. For comparison, they used Australian Aboriginal DNA data that had already been analyzed and published by colleagues. After comparing the two groups, they came to a startling conclusion: two specific genetic mutations on the mtDNA of the Indian and aboriginal samples matched perfectly. Not only that, but these particular mutations do not exist elsewhere in the world; they are shared exclusively between a few isolated tribes in India and native Australians.

Kumar and his colleagues concluded the two groups must share a common ancestry. To lend further credence to their theory, they calculated the date when the ancestors of the Indian tribes and Aborigines must have split.

Their calculations produced a date of 55,000 years ago, a time when early humans in India were probably hunting wildlife and gathering plant foods. Some of their descendants eventually formed tribes like the Baiga and Birhor; others moved eastward, traversing southeastern Asian and then using maritime technology to cross nearly 60 miles of open ocean between Indonesia and New Guinea.

After arriving in Australia, they moved into the heart of the Australian Outback. A few thousand years later, a direct descendant of these ancient explorers was laid to rest along the shores of Lake Mungo.

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The Neanderthals have always held a special place in the field of anthropology.  The skeletal remains of our short, stocky evolutionary relatives have been found everywhere from Spain to Iraq.

Their physical likeness to our own species, and the possibility that humans and Neanderthals may have interacted, has long fascinated experts and enthusiastic novices alike.  But simply studying their skeletal remains and artifacts seemed to leave more questions than answers.

More than 10 years ago an international team of scientists became the first to extract and analyze ancient DNA (aDNA) from a Neanderthal skeleton. By examining the mitochondrial DNA (mtDNA) — which is more abundant in our cells than our nuclear DNA and therefore more likely to preserve — they found that there were enough genetic differences between this Neanderthal and modern humans to classify the two as separate species.

Since this initial foray into Neanderthal genetics there have been attempts to improve aDNA analysis, with the goal of filling in the gaps that traditional anthropological techniques had been unable to.  Earlier this year, scientists at the Max Planck Institute for Evolutionary Anthropology became the first to sequence the entire Neanderthal mitochondrial genome – no easy feat. Now scientists have taken aDNA analysis to the next level by developing a novel technique to extract it more easily, yielding the most comprehensive and accurate results to date.  Along the way, they have uncovered some intriguing clues to the possible fate of the Neanderthals. Their results are reported in the July 17 issue of Science.

This new study, also led by Max Planck Institute scientists, centers around a novel method for finding and extracting that elusive aDNA from Neanderthal remains. The study took advantage of a new kind of aDNA extraction process, called Primer Extension Capture (PEC). This technique has many advantages over the others, primarily because it allows the aDNA to be completely isolated from all the other molecular junk  that can accumulate over time. This yields highly accurate results with much less effort. So instead of simply using this technique on one Neanderthal individual, they analyzed five.

The remains they chose had been excavated from a variety of locations, from Croatia to Germany to Spain and Russia.  Most of the remains were between 35,000 and 40,000 years old, which is very close to when Neanderthals were believed to have disappeared from most of their range.  They also examined Neanderthal remains from Russia that dated to between 60,000 and 70,000 years old.

After successfully extracting and analyzing the DNA of these remains, the researchers came to a few startling conclusions.  First, the level of genetic diversity among the samples was exceedingly low.  In fact, the amount of genetic diversity of the Neanderthal samples was less than one-third the diversity we see in modern humans today. For example, two of the samples — one from Croatia and the other from Germany — had identical mtDNA genomes. For two individuals living nearly 1,000 miles apart, this is quite unusual; unless there wasn’t much variation in mtDNA in the first place.

The authors of this report think this genetic homogeneity means that there were far fewer Neanderthals living in Europe and western Asia than they’d previously thought. Based on their analysis of the five individuals, the they estimated that the total population size of Neanderthals in Europe 35,000 years ago may have had as few as 3,500 females (because mtDNA is passed down maternally, it cannot be used to estimate male population size).

The authors believe there are two possible explanations for this small population size.  The first is that, over the 400,000 year history of Neanderthals, their population may have always been small.  After all, for much of their existence they survived harsh ice age conditions, so low population size may have been necessary for survival.

But the authors offer an alternate explanation as well. They think this small population size is the result of long-term population decline, perhaps beginning about 40,000 years ago and continuing until Neanderthals were wiped out. To test their hypothesis, the researchers re-analyzed the Neanderthal mtDNA genomes and found that their protein-encoding genes had evolved much more quickly than those of humans or chimpanzees since the three species split, millions of years ago.

This high rate of evolution, the authors argue, was not present in the older Russian Neanderthal sample.  This fact implies a pattern of decline in population size, not a population that had been small from the start. These results support their idea that the Neanderthal numbers were on the decline.  Without direct evidence, they can only speculate as to the cause of of their decline, but the scientists believe it may be tied to the arrival of humans in Europe and western Asia about 40,000 years ago.

Today most experts believe the Neanderthals were being out-competed by the incoming humans, who had superior technology and language skills.  Over time, the Neanderthals were forced to move to more isolated regions in the mountains of France and Spain.  By 30,000 years ago, only a few traces remained.  Soon after, they were gone.  This study reveals some compelling evidence that humans were in fact responsible – whether directly or indirectly – for the demise of the Neanderthals.

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