Thursday, March 15, 2018

Modern humans interbred with Denisovans twice in history

This graphical abstract shows two waves of Denisovan ancestry have shaped present-day humans. 
Credit: Browning et al./Cell
Modern humans co-existed and interbred not only with Neanderthals, but also with another species of archaic humans, the mysterious Denisovans. While developing a new genome-analysis method for comparing whole genomes between modern human and Denisovan populations, researchers unexpectedly discovered two distinct episodes of Denisovan genetic intermixing, or admixing, between the two. This suggests a more diverse genetic history than previously thought between the Denisovans and modern humans.

In a paper published in Cell on March 15, scientists at the University of Washington in Seattle determined that the genomes of two groups of modern humans with Denisovan ancestry--individuals from Oceania and individuals from East Asia--are uniquely different, indicating that there were two separate episodes of Denisovan admixture.

"What was known already was that Oceanian individuals, notably Papuan individuals, have significant amounts of Denisovan ancestry," says senior author Sharon Browning, a research professor of biostatistics, University of Washington School of Public Health. The genomes of modern Papuan individuals contain approximately 5% Denisovan ancestry."

Researchers also knew Denisovan ancestry is present to a lesser degree throughout Asia. The assumption was that the ancestry in Asia was achieved through migration, coming from Oceanian populations. "But in this new work with East Asians, we find a second set of Denisovan ancestry that we do not find in the South Asians and Papuans," she says. "This Denisovan ancestry in East Asians seems to be something they acquired themselves."

After studying more than 5,600 whole-genome sequences from individuals from Europe, Asia, America, and Oceania and comparing them to the Denisovan genome, Browning and colleagues determined that the Denisovan genome is more closely related to the modern East Asian population than to modern Papuans. "We analyzed all of the genomes searching for sections of DNA that looked like they came from Denisovans," says Browning, whose team relied on genomic information from the UK10K project, the 1000 Genomes Project, and the Simons Genome Diversity Project.

"When we compared pieces of DNA from the Papuans against the Denisovan genome, many sequences were similar enough to declare a match, but some of the DNA sequences in the East Asians, notably Han Chinese, Chinese Dai, and Japanese, were a much closer match with the Denisovan," she says.

What is known about Denisovan ancestry comes from a single set of archaic human fossils found in the Altai mountains in Siberia. That individual's genome was published in 2010, and other researchers quickly identified segments of Denisovan ancestry in several modern-day populations, most significantly with individuals from Oceania but also in East and South Asians.

"The assumption is that admixing with Denisovans occurred fairly quickly after humans moved out of Africa, around 50,000 years ago, but we do not know where in terms of location," Browning says. She theorizes that perhaps the ancestors of Oceanians admixed with a southern group of Denisovans while the ancestors of East Asians admixed with a northern group.

Going forward, the researchers plan on studying more Asian populations and others throughout the world, including Native Americans and Africans. "We want to look throughout the world to see if we can find evidence of interbreeding with other archaic humans," says Browning. "There are signs that intermixing with archaic humans was occurring in Africa, but given the warmer climate no one has yet found African archaic human fossils with sufficient DNA for sequencing."

Genomic ancestry of Stone Age North Africans from Morocco discovered

An international team of researchers, led by Johannes Krause and Choongwon Jeong from the Max Planck Institute for the Science of Human History (Jena, Germany), and Abdeljalil Bouzouggar from the Institut National des Sciences de l'Archéologie et du Patrimoine (Rabat, Morocco) and including scientists from the Mohammed V University in Rabat, the Natural History Museum in London, University of Oxford, Université Mohammed Premier in Oujda and the Max Planck Institute for Evolutionary Anthropology in Leipzig, have sequenced DNA from individuals from Morocco dating to approximately 15,000 years ago, as published in Science.

This is the oldest nuclear DNA from Africa ever successfully analyzed. The individuals, dating to the Late Stone Age, had a genetic heritage that was in part similar to Near Eastern populations and in part related to sub-Saharan African populations.

North Africa is an important area in the history of the evolution of our species. The geography of North Africa also makes it an interesting area for studying how humans expanded out of Africa. It is part of the African continent, but the Sahara desert presents a substantial barrier to travel to and from southern regions. Similarly, it is part of the Mediterranean region, but in the past the sea could have presented a barrier to interaction with others as well. "A better understanding of the history of North Africa is critical to understanding the history of our species," explains co-author Saaïd Amzazi of Mohammed V University in Rabat, Morocco.

In order to address this, the team looked at a burial site in Grotte des Pigeons, near Taforalt in Morocco, associated with the Later Stone Age Iberomaurusian culture. The Iberomaurusians are believed to be the first in the area to produce finer stone tools known as microliths. "Grotte des Pigeons is a crucial site to understanding the human history of north-western Africa, since modern humans frequently inhabited this cave intensively during prolonged periods throughout the Middle and Later Stone Age," explains co-author Louise Humphrey of the Natural History Museum in London. "Around 15,000 years ago there is evidence for more intensive use of the site and the Iberomaurusians started to bury their dead at the back of the cave."

15,000-year-old nuclear DNA is the oldest recovered in Africa
The researchers analyzed DNA from nine individuals from Taforalt using advanced sequencing and analytical methods. They were able to recover mitochondrial data from seven of the individuals and genome-wide nuclear data from five of the individuals. Because of the age of the samples, at approximately 15,000 years old, and the poor preservation characteristic of the area, this is an unprecedented achievement. "This is the first and the oldest Pleistocene DNA of our species recovered in Africa," explains co-senior author Abdeljalil Bouzouggar.

"Due to challenging conditions for DNA preservation, relatively few ancient genomes have been recovered from Africa and none of them so far predate the introduction of agriculture in North Africa," explains first author Marieke van de Loosdrecht of the Max Planck Institute for the Science of Human History. "Successful genome reconstruction was possible by using specialized laboratory methods to retrieve highly degraded DNA, and relatively new analysis methods to characterize the genetic profiles of these individuals."

The researchers found two major components to the genetic heritage of the individuals. About two-thirds of their heritage is related to contemporaneous populations from the Levant and about one-third is most similar to modern sub-Saharan Africans, in particular West Africans.

As early as the Stone Age, human populations had links that stretched across continents
The high proportion of Near Eastern ancestry shows that the connection between North Africa and the Near East began much earlier than many previously thought. Although the connections between these regions have been shown in previous studies for more recent time periods, it was not generally believed that humans were interacting across these distances during the Stone Age. "Our analysis shows that North Africa and the Near East, even at this early time, were part of one region without much of a genetic barrier," explains co-senior author Choongwon Jeong.

Although the Sahara did present a physical barrier, there was also clearly interaction happening at this time. The strong connection between the Taforalt individuals and sub-Saharan populations shows that interactions across this vast desert were occurring much earlier than was previously thought. In fact, the proportion of sub-Saharan ancestry of the Taforalt individuals, one-third, is a higher percentage than found in modern populations in Morocco and many other North African populations.

Sub-Saharan heritage from a previously unknown ancient population
Though the scientists found clear markers linking the heritage in question to sub-Saharan Africa, no previously identified population has the precise combination of genetic markers that the Taforalt individuals had. While some aspects match modern Hadza hunter-gatherers from East Africa and others match modern West Africans, neither of these groups has the same combination of characteristics as the Taforalt individuals. Consequently, the researchers cannot be sure exactly where this heritage comes from. One possibility is that this heritage may come from a population that no longer exists. However, this question would need further investigation.

"Clearly, human populations were interacting much more with groups from other, more distant areas than was previously assumed," states co-senior author Johannes Krause, director of the Department of Archaeogenetics at the Max Planck Institute for the Science of Human History. "This illustrates the ability of ancient genetics to add to our understanding of human history." Further studies in this region could help to clarify more about when and how these different populations interacted and where they came from.

New evidence of early human innovation, pushing back evolutionary timeline

An international collaboration, including the Natural History Museum of Utah at the University of Utah, have discovered that early humans in eastern Africa had--by about 320,000 years ago--begun trading with distant groups, using color pigments and manufacturing more sophisticated tools than those of the Early Stone Age. These newly discovered activities approximately date to the oldest known fossil record of Homo sapiens and occur tens of thousands of years earlier than previous evidence from eastern Africa. These behaviors, which are characteristic of humans who lived during the Middle Stone Age, replaced technologies and ways of life that had been in place for hundreds of thousands of years.

Evidence for these milestones in humans' evolutionary past comes from the Olorgesailie Basin in southern Kenya, which holds an archeological record of early human life spanning more than a million years. The new discoveries, reported in three studies published March 15 in the journal Science, indicate that these behaviors emerged during a period of tremendous environmental variability in the region. As earthquakes remodeled the landscape and climate fluctuated between wet and dry conditions, technological innovation, social exchange networks and early symbolic communication would have helped early humans survive and obtain the resources they needed despite unpredictable conditions, the scientists say.

"These behavioral innovations may very well represent a response to rapid changes in the environment," said Tyler Faith, curator of archaeology at the Natural History Museum of Utah, assistant professor of anthropology at the U, and coauthor of one of the three studies. "Such a response would have helped human populations endure climatic and environmental shifts that likely contributed to the demise of many other species in the region."

To better understand how climactic instability might have influenced the ecosystems in which the early humans at Olorgesailie lived, the research team integrated data from a variety of sources to assess and reconstruct the ancient environment. Faith and collaborators analyzed large mammal fossils from the archaeological sites. The bones told a story of massive turnover in the region--most species previously common in the Olorgesailie Basin had disappeared, and were replaced by others previously unknown in the basin. Some of the new ones are familiar species found in eastern Africa today, though others--including a massive zebra--are now extinct.

The team also saw evidence of dramatic range shifts, with some animals--such as the springbok, an antelope known today only from southern Africa--appearing in the basin. The faunal evidence, together with additional geological and paleoenvironmental indicators from Olorgesailie, show that the new adaptive behaviors that define earliest Homo sapiens were associated with large-scale changes in climates, faunas, and landscapes.

Rick Potts, director of the National Museum of Natural History's Human Origins Program, is the lead author on one of the three Science publications that describe the adaptive challenges that early humans faced during this phase of evolution, to which Faith contributed. Alison Brooks, professor of anthropology at George Washington University's Center for the Advanced Study of Human Paleobiology and an associate of the museum's Human Origins Program, is lead author on the paper that focuses on the evidence of early resource exchange and use of coloring materials in the Olorgesailie Basin. A third paper, by Alan Deino at the Berkeley Geochronology Center and colleagues, details the chronology of the Middle Stone Age discoveries.

The first evidence of human life in the Olorgesailie Basin comes from about 1.2 million years ago. For hundreds of the thousands of years, people living there made and used large stone-cutting tools called handaxes. Beginning in 2002, the Human Origins Program team discovered a variety of smaller, more carefully shaped tools in the basin. Isotopic dating by Deino and collaborators revealed that the tools were surprisingly old--made between 320,000and 305,000 years ago. These tools were carefully crafted and more specialized than the large, all-purpose handaxes. While the handaxes of the earlier era were manufactured using local stones, the Smithsonian team found small stone points made of non-local obsidian at their Middle Stone Age sites.

The team also found larger, unshaped pieces of the sharp-edged volcanic stone at Olorgesailie, which has no obsidian source of its own. The diverse chemical composition of the artifacts matches that of a wide range of obsidian sources in multiple directions 15 to 55 miles away, suggesting exchange networks were in place to move the valuable stone across the ancient landscape.

The team also discovered black and red rocks--manganese and ocher--at the sites, along with evidence that the rocks had been processed for use as coloring material. "We don't know what the coloring was used on, but coloring is often taken by archeologists as the root of complex symbolic communication," Potts said. "Just as color is used today in clothing or flags to express identity, these pigments may have helped people communicate membership in alliances and maintain ties with distant groups."

Tuesday, March 13, 2018

Genetic prehistory of Iberia differs from central and northern Europe

In a multidisciplinary study published in PNAS, an international team of researchers combined archaeological, genetic and stable isotope data to encapsulate 4000 years of Iberian biomolecular prehistory.

The team analyzed human remains of 13 individuals from the north and south of Spain, including the rich archaeological site of El Portalón, which forms part of the well-known site of Atapuerca in Burgos and in itself harbors 4 millennia of Iberian prehistory. The study also involved important sites like Cueva de los Murciélagos in Andalusia, from which the genome of a 7 245 year-old Neolithic farmer was sequenced making it the oldest sequenced genome in southern Iberia representing the Neolithic Almagra Pottery Culture - the early agriculturalists of southern Spain.

Prehistoric migrations have played an important role in shaping the genetic makeup of European populations. After the last glacial maximum about 20 000 years ago, Europe was inhabited by hunter-gatherer groups and two major migrations during the last 10 000 years had massive impacts on lifestyle and gene pool of European populations.

First, groups originally coming from the Middle East and Anatolia introduced farming practices to Europe during the Neolithic. Less than 5 000 years ago, herder groups from the Pontic-Caspian steppe spread over the European continent. As both of these movements originated in the east, the most western parts of the continent were last to be reached by these migrations. While archaeogenetic studies have shown that both of these migrations have replaced more than half of the gene pool in Central and Northern Europe, much less is known about the influence of these events in Iberian populations, particularly in the most southern areas such as Andalusia.

Two independent migrations spread farming practices across Europe
The first farmers mainly reached Iberia following a coastal route through the northern Mediterranean Sea. The new study demonstrates that Neolithic Iberians show genetic differences to the migrant farmers that settled in Central and Northern Europe. "This suggests that all early farmers in Iberia trace most of their ancestry to the first Neolithic people that migrated into the peninsula and that later contributions from their central European counterparts were only minor", says archaeogeneticist Cristina Valdiosera from La Trobe University in Australia, one of the lead authors of the study.

These Mediterranean route migrants show a strong genetic connection with the modern-day inhabitants of the Mediterranean island of Sardinia. "We can probably consider modern Sardinians relatively direct descendants of the people who spread farming practices across the Mediterranean region around 8 000 years ago", adds Mattias Jakobsson, population geneticist at Uppsala University, Sweden and one of the senior authors of the study.

First wave of eastern migration involved small number of individuals
Despite potential other entrances into Iberia, such as North Africa or mainland Europe, the researchers did not find substantial regional differences within Iberia. Uppsala University's Torsten Günther, population geneticist and one of the lead authors of this study, says: "While geographic differences seem minor, we do see some differences over time due to interaction and genetic exchange between groups."

The first Iberian farmers show remarkably low levels of genetic diversity, indicating that the first wave of eastern migration to establish itself on the peninsula was relatively small. Following this initial period of low diversity, the newly arrived populations grew in size and mixed with the local hunter-gatherers, rapidly increasing genetic diversity during later periods.

Low genetic impact of later/Bronze Age migrations in Iberia While recent studies have demonstrated that a massive migration of Pontic-Caspian steppe herders during the Late Neolithic/Bronze Age transition is responsible for a major population turnover in central and northern Europe, the authors report in this study that the genetic influence of this migration on contemporary southwestern Europeans, namely the prehistoric Iberians, was only minor. This confirms that the genetic history of Iberia was unique as it has mostly been influenced by the main prehistoric migration associated with the introduction of farming practices - the Neolithic Revolution.

Homogenous diet in Iberian farmers
The authors also investigated the diet of these Neolithic farmers throughout almost 4000 years corroborating that despite the significant biological interaction between culturally different groups the farming culture predominated from the very beginning and continued over time. Molecular archaeologist Colin Smith from La Trobe University, one of the senior authors, explains: "Interestingly, while we do see a substantial genetic influx of hunter-gatherer ancestry into farmers over time, the diet of these early farmers does not change. Their terrestrial diet is characteristic of farming cultures and persist temporally and geographically across the millennia".

The study illustrates the power of interdisciplinary research to understand the full complexity of European prehistory. "Overall, these results emphasize the differences between the westernmost populations and their central European counterparts and highlight the need for detailed regional studies to reveal the full complexity of prehistoric migrations", Dr. Valdiosera concludes.

Modern humans flourished through ancient supervolcano eruption 74,000 years ago

Imagine a year in Africa that summer never arrives. The sky takes on a gray hue during the day and glows red at night. Flowers do not bloom. Trees die in the winter. Large mammals like antelope become thin, starve and provide little fat to the predators (carnivores and human hunters) that depend on them. Then, this same disheartening cycle repeats itself, year after year. This is a picture of life on earth after the eruption of the super-volcano, Mount Toba in Indonesia, about 74,000 years ago. In a paper published this week in Nature, scientists show that early modern humans on the coast of South Africa thrived through this event.

An eruption a hundred times smaller than Mount Toba - that of Mount Tambora, also in Indonesia, in 1815 - is thought to have been responsible for a year without summer in 1816. The impact on the human population was dire - crop failures in Eurasia and North America, famine and mass migrations. The effect of Mount Toba, a super-volcano that dwarfs even the massive Yellowstone eruptions of the deeper past, would have had a much larger, and longer-felt, impact on people around the globe.

The scale of the ash-fall alone attests to the magnitude of the environmental disaster. Huge quantities of aerosols injected high into the atmosphere would have severely diminished sunlight - with estimates ranging from a 25 to 90 percent reduction in light. Under these conditions, plant die-off is predictable, and there is evidence of significant drying, wildfires and plant community change in East Africa just after the Toba eruption.

If Mount Tambora created such devastation over a full year - and Tambora was a hiccup compared to Toba - we can imagine a worldwide catastrophe with the Toba eruption, an event lasting several years and pushing life to the brink of extinctions.

In Indonesia, the source of the destruction would have been evident to terrified witnesses - just before they died. However, as a family of hunter-gatherers in Africa 74,000 years ago, you would have had no clue as to the reason for the sudden and devastating change in the weather. Famine sets in and the very young and old die. Your social groups are devastated, and your society is on the brink of collapse.

The effect of the Toba eruption would have certainly impacted some ecosystems more than others, possibly creating areas - called refugia - in which some human groups did better than others throughout the event. Whether or not your group lived in such a refuge would have largely depended on the type of resources available. Coastal resources, like shellfish, are highly nutritious and less susceptible to the eruption than the plants and animals of inland areas.

When the column of fire, smoke and debris blasted out the top of Mount Toba, it spewed rock, gas and tiny microscopic pieces (cryptotephra) of glass that, under a microscope, have a characteristic hook shape produced when the glass fractures across a bubble. Pumped into the atmosphere, these invisible fragments spread across the world.

Panagiotis (Takis) Karkanas, director of the Malcolm H. Wiener Laboratory for Archaeological Science, American School of Classical Studies, Greece, saw a single shard of this explosion under a microscope in a slice of archaeological sediment encased in resin.

"It was one shard particle out of millions of other mineral particles that I was investigating. But it was there, and it couldn't be anything else," says Karkanas.

The shard came from an archaeological site in a rockshelter called Pinnacle Point 5-6, on the south coast of South Africa near the town of Mossel Bay. The sediments dated to about 74,000 years ago.

"Takis and I had discussed the potential of finding the Toba shards in the sediments of our archaeological site, and with his eagle eye, he found one," explains Curtis W. Marean, project director of the Pinnacle Point excavations. Marean is the associate director of the Institute of Human Origins at Arizona State University and honorary professor at the Centre for Coastal Palaeoscience at Nelson Mandela University, South Africa.

Marean showed the shard image to Eugene Smith, a volcanologist with the University of Nevada at Las Vegas, and Smith confirmed it was a volcanic shard.

"The Pinnacle Point study brought me back to the study of glass shards from my master's thesis 40 years earlier," says Smith.

Early in the study, the team brought in expert cryptotephra scientist Christine Lane who trained graduate student Amber Ciravolo in the needed techniques. Racheal Johnsen later joined Ciravalo as lab manager and developed new techniques.

From scratch, with National Science Foundation support, they developed the Cryptotephra Laboratory for Archaeological and Geological Research, which is now involved in projects not only in Africa, but in Italy, Nevada and Utah.

Encased in that shard of volcanic glass is a distinct chemical signature, a fingerprint that scientists can use to trace to the killer eruption. In their paper in Nature, the team describes finding these shards in two archaeological sites in coastal South Africa, tracing those shards to Toba through chemical fingerprinting and documenting a continuous human occupation across the volcanic event.

"Many previous studies have tried to test the hypothesis that Toba devastated human populations," Marean notes. "But they have failed because they have been unable to present definitive evidence linking a human occupation to the exact moment of the event."

Most studies have looked at whether or not Toba caused environmental change. It did, but such studies lack the archaeological data needed to show how Toba affected humans.

The Pinnacle Point team has been at the forefront of development and application of highly advanced archaeological techniques. They measure everything on site to millimetric accuracy with a "total station," a laser-measurement device integrated to handheld computers for precise and error-free recording.

Naomi Cleghorn with the University of Texas at Arlington, recorded the Pinnacle Point samples as they were removed.

Cleghorn explains, "We collected a long column of samples - digging out a small amount of sediment from the wall of our previous excavation. Each time we collected a sample, we shot its position with the total station. We could then precisely compare the position of the sample to our excavated cultural remains - the trash ancient humans left at the site. We could also compare our cryptotephra sample position with that of samples taken for dating and environmental analyses."

In addition to understanding how Toba affected humans in this region, the study has other important implications for archaeological dating techniques. Archaeological dates at these age ranges are imprecise - 10 percent (or 1000s of years) error is typical. Toba ash-fall, however, was a very quick event that has been precisely dated. The time of shard deposition was likely about two weeks in duration - instantaneous in geological terms.

"We found the shards at two sites," explains Marean. "The Pinnacle Point rockshelter (where people lived, ate, worked and slept) and an open air site about 10 kilometers away called Vleesbaai. This latter site is where a group of people, possibly members of the same group as those at Pinnacle Point, sat in a small circle and made stone tools. Finding the shards at both sites allows us to link these two records at almost the same moment in time."

Not only that, but the shard location allows the scientists to provide an independent test of the age of the site estimated by other techniques. People lived at the Pinnacle Point 5-6 site from 90,000 to 50,000 years ago. Zenobia Jacobs with the University of Wollongong, Australia, used optically stimulated luminescence (OSL) to date 90 samples and develop a model of the age of all the layers. OSL dates the last time individual sand grains were exposed to light.

"There has been some debate over the accuracy of OSL dating, but Jacobs' age model dated the layers where we found the Toba shards to about 74,000 years ago - right on the money," says Marean. This lends very strong support to Jacobs' cutting-edge approach to OSL dating, which she has applied to sites across southern Africa and the world.

"OSL dating is the workhorse method for construction of timelines for a large part of our own history. Testing whether the clock ticks at the correct rate is important. So getting this degree of confirmation is pleasing," says Jacobs.

In the 1990s, scientists began arguing that this eruption of Mount Toba, the most powerful in the last two million years, caused a long-lived volcanic winter that may have devastated the ecosystems of the world and caused widespread population crashes, perhaps even a near-extinction event in our own lineage, a so-called bottleneck.

This study shows that along the food-rich coastline of southern Africa, people thrived through this mega-eruption, perhaps because of the uniquely rich food regime on this coastline. Now other research teams can take the new and advanced methods developed in this study and apply them to their sites elsewhere in Africa so researchers can see if this was the only population that made it through these devastating times.

New insights into the origin of elongated heads in early medieval Germany


This is an artificially deformed female skull from Altenerding, an Earyl Medieavel site in Bavaria. Skull deformations like this were formerly attributed to the Huns. However, the new palaeogenomic study shows that while this individual carries Central Asian genetic components, in all likelihood she migrated from the Black Sea region to Bavaria along with other women around 500 AD.

Credit: State Collection for Anthropology and Palaeoanatomy Munich
The transition from Late Antiquity to the Middle Ages in Europe is marked by two key events in European history, i.e., the fall of the Western Roman Empire and the migration into this Empire by various barbarian tribes such as the Goths, Alemanni, Franks, and Lombards. This resulted in a profound cultural and socioeconomic transformation throughout the continent, and many settlements from this epoch would subsequently develop into the villages and towns we still know today.

An international team led by anthropologist Dr. Michaela Harbeck from the Bavarian State Collection for Anthropology and Palaeoanatomy (SAPM) and population geneticist Professor Joachim Burger of Johannes Gutenberg University Mainz (JGU) has now performed the first genomic analysis of populations that lived on the former territory of the Roman Empire in Bavaria, Germany, from around 500 AD and provided the first direct look at the complex population dynamics of what has popularly been known as the Migration Period, or "Völkerwanderung" in German.

In an interdisciplinary study funded by the Volkswagen Foundation, the international research team analyzed the ancient genomes of almost 40 early medieval people from southern Germany. While most of the ancient Bavarians looked genetically like Central and Northern Europeans, one group of individuals had a very different and diverse genetic profile. Members of this group were particularly notable in that they were women whose skulls had been artificially deformed at birth. Such enigmatic deformations give the skull a characteristic tower shape and have been found in past populations from across the world and from different periods of time.

"Parents wrapped their children's heads with bandages for a few months after birth in order to achieve the desired head shape," explained Dr. Michaela Harbeck. "It is difficult to answer why they carried out this elaborate process, but it was probably used to emulate a certain ideal of beauty or perhaps to indicate a group affiliation."

So far, scholars have only speculated about origins of the practice in medieval Europe. "The presence of these elongated skulls in parts of eastern Europe is most commonly attributed to the nomadic Huns, led by Atilla, during their invasion of the Roman Empire from Asia, but the appearance of these skulls in western Europe is more mysterious, as this was very much the fringes of their territory," said Dr. Krishna Veeramah, first author of the study.

By analyzing DNA obtained from these elongated skulls, Professor Joachim Burger's team revealed that these women likely migrated to early Bavarian settlements from eastern Europe. "Although there is evidence that there was some genetic contribution from Central Asia, the genomic analysis points to the fact that women with deformed skulls in this region are genetically most similar to today's south eastern Europeans, and that the Huns likely played only a minor role in directly transmitting this tradition to Bavaria," Burger noted. Besides their deformed skulls, these women also tended to have darker hair and eye color than the other Bavarians they were buried and probably lived with, who primarily had fair hair and blue eyes.

But the migration of females to Bavaria did not only involve those possessing elongated skulls. Only a little later, two women can be identified who most closely resemble modern Greeks and Turks. In contrast, there was no evidence of men with drastically different genetic profiles. "Most of these foreign women are found with grave goods that look unremarkable compared to the rest of the buried population," added Veeramah. "These cases of female migration would have been invisible from the material culture alone."

"This is an example of long-range female mobility that bridges larger cultural spaces and may have been a way for distant groups to form new strategic alliances during this time of great political upheaval in the absence of a previous Roman hegemony," stated Burger. "We must expect that many more unprecedented population-dynamic phenomena have contributed to the genesis of our early cities and villages."

"Interestingly, though our results are preliminary, there are no major traces of genetic ancestry in these early inhabitants of Bavaria that might have come from soldiers of the Roman army," said Harbeck. "We need to keep investigating on an even broader basis how much Celtic and Roman ancestry is in these early Bavarians."

Compassion helped Neanderthals to survive

They have an unwarranted image as brutish and uncaring, but new research has revealed just how knowledgeable and effective Neanderthal healthcare was.

The study, by the University of York, reveals that Neanderthal healthcare was uncalculated and highly effective - challenging our notions that they were brutish compared to modern humans.

The researchers argue that the care provided was widespread and should be seen as a "compassionate and knowledgeable response to injury and illness."

It is well known that Neanderthals sometimes provided care for the injured, but new analysis by the team at York suggest they were genuinely caring of their peers, regardless of the level of illness or injury, rather than helping others out of self-interest.

Lead author, Dr Penny Spikins, senior lecturer in the Archaeology of Human Origin at the University of York, said: "Our findings suggest Neanderthals didn't think in terms of whether others might repay their efforts, they just responded to their feelings about seeing their loved ones suffering."

Most of the individuals archaeologists know about had a severe injury of some kind, with detailed pathologies highlighting a range of debilitating conditions and injuries.

In some cases the injuries occurred long before death and would have required monitoring, massage, fever management and hygiene care, the study suggests.

Analysis of a male aged around 25-40 at time of death revealed a catalogue of poor heath, including a degenerative disease of the spine and shoulders.

His condition would have sapped his strength over the final 12 months of life and severely restricted his ability to contribute to the group.

Yet, the authors of the study argue he remained part of the group as his articulated remains were subsequently carefully buried.

Dr Spikins added: "We argue that the social significance of the broader pattern of healthcare has been overlooked and interpretations of a limited or calculated response to healthcare have been influenced by preconceptions of Neanderthals as being 'different' and even brutish. However, a detailed consideration of the evidence in its social and cultural context reveals a different picture.

"The very similarity of Neanderthal healthcare to that of later periods has important implications. We argue that organised, knowledgeable and caring healthcare is not unique to our species but rather has a long evolutionary history."

The study was partially supported by the John Templeton Foundation and published in the journal World Archaeology.