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November 2014
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Mission to discover hundreds of black holes could unlock secrets of the Universe

Researchers have made a breakthrough in helping scientists discover hundreds of black holes throughout the universe. When two detectors are switched on in the US next year, scientists hope to pick up the faint ripples of black hole collisions millions of years ago, known as gravitational waves. Black holes cannot be seen, but scientists hope the revamped detectors — which act like giant microphones — will find remnants of black hole collisions.
This is an illustration of a three-dimensional simulation of merging black holes. The simulation provides the foundation to explore the universe in an entirely new way, through the detection of gravitational waves. Credit: Henze, NASA

This is an illustration of a three-dimensional simulation of merging black holes. The simulation provides the foundation to explore the universe in an entirely new way, through the detection of gravitational waves.
Credit: Henze, NASA

When two detectors are switched on in the US next year, the Cardiff team hope their research will help scientists pick up the faint ripples of black hole collisions millions of years ago, known as gravitational waves.

Black holes cannot be seen, but scientists hope the revamped detectors — which act like giant microphones — will find remnants of black hole collisions.

Led by Dr Mark Hannam from the School of Physics and Astronomy, the researchers have built a theoretical model which aims to predict all potential gravitational-wave signals that might be found by the detectors.

The Cardiff researchers hope it will act as a ‘spotters’ guide’ to help scientists working with the giant LIGO detectors recognise the right waveforms and reveal the secrets of how black holes orbit into each other and collide.

Dr Hannam said: “The rapid spinning of black holes will cause the orbits to wobble, just like the last wobbles of a spinning top before it falls over. These wobbles can make the black holes trace out wild paths around each other, leading to extremely complicated gravitational-wave signals. Our model aims to predict this behaviour and help scientists find the signals in the detector data.”

The Cardiff team, which includes postdoctoral researchers, PhD students, and collaborators from universities in Europe and the United States, will work with scientists across the world as they attempt to unravel the origins of the Universe.

Dr Hannam added: “Sometimes the orbits of these spinning black holes look completely tangled up, like a ball of string. But if you imagine whirling around with the black holes, then it all looks much clearer, and we can write down equations to describe what is happening. It’s like watching a kid on a high-speed spinning amusement park ride, apparently waving their hands around. From the side lines, it’s impossible to tell what they’re doing. But if you sit next to them, they might be sitting perfectly still, just giving you the thumbs up.”

The new model has been programmed into the computer codes that LIGO scientists all over the world are preparing to use to search for black-hole mergers when the detectors switch on. But there is still more work to do.

“So far we’ve only included these precession effects while the black holes spiral towards each other,” said Dr Hannam. “We still need to work our exactly what the spins do when the black holes collide.”

For that they need to perform large computer simulations to solve Einstein’s equations for the moments before and after the collision. They’ll need to produce many simulations to capture enough combinations of black-hole masses and spin directions to understand the overall behaviour of these complicated systems.

Dr Hannam is optimistic. “For years we were stumped on how to untangle the black-hole motion. Now that we’ve solved that, we know what to do next.”

Reference: Mark Hannam, Patricia Schmidt, Alejandro Bohé, Leïla Haegel, Sascha Husa, Frank Ohme, Geraint Pratten, Michael Pürrer. Simple Model of Complete Precessing Black-Hole-Binary Gravitational Waveforms. Physical Review Letters, 2014; 113 (15) DOI: 10.1103/PhysRevLett.113.151101

Advancing new tools to fill in the microbial tree of life

Scientists suggest why the time is right to apply genomic technologies to discover new life on Earth. ‘Nature has been tinkering with life for at least three billion years and we now have a new set of ways to look for novel forms of life that have so far eluded discovery.’
DOE Joint Genome Institute researchers are illuminating new branches of the tree of life by characterizing novel microbes sourced from extreme, inhospitable and isolated environments, which they expect to be preferred niches for early life, potentially sheltered from more modern microbial competitors. Credit: Berkeley Lab-Zosia Rostomian

DOE Joint Genome Institute researchers are illuminating new branches of the tree of life by characterizing novel microbes sourced from extreme, inhospitable and isolated environments, which they expect to be preferred niches for early life, potentially sheltered from more modern microbial competitors.
Credit: Berkeley Lab-Zosia Rostomian

 “We are poised, armed with a new toolkit of powerful genomic technologies to generate and mine the increasingly large datasets to discover new life that may be strikingly different from those that we catalogued thus far,” said Rubin. “Nature has been tinkering with life for at least three billion years and we now have a new set of ways to look for novel life that have so far eluded discovery.”

“Massive-scale metagenomic sequencing of environmental DNA and RNA samples should, in principle, generate sequence data from any entity for which nucleic acids can be extracted,” Rubin noted. “Analysis of these data to identify outliers to previously defined life represents a powerful means to explore the unknown.”

In addition, Rubin pointed to the advent of single-cell sequencing with microfluidic and cell sorting approaches, focused specifically on cells that lack genes that match previously identified ones, as another approach in the search for completely novel organisms.

“We also need to choose particularly suitable environmental niches so that we are not just looking, ‘under the street lamp’ — at environments that we have already previously studied.”

Rubin suggested targets for the discovery of novel life including extreme, inhospitable and isolated environments that are expected to be preferred niches for early life, potentially sheltered from more modern microbial competitors. This would include low oxygen subsurface sites with environmental conditions predating the Great Oxidation Event that occurred about 2.3 billion years ago when the atmosphere went from very low to high oxygen concentrations. Support for the idea that isolated low-oxygen environments may be preferred niches for early life comes from observations that anaerobic niches deep within Earth’s crust tend to harbor ancient branches within the domains of life.

There is no lack of opportunities for exploring the planet’s microbial diversity, Rubin said. “Students contemplating careers may be well served to join the legions of 21st Century cartographers, who, like the DOE JGI user community, are interpreting the coordinates generated by the tools of genomics and other advanced omics to map the metabolic potential of the planet.”

Among the thousands of environmental sequencing targets that make up the DOE JGI’s compendium of genome projects, some mirror the challenges that the Ancient Mariner encountered along the ship’s voyage: “driven by storms to the cold Country towards the South Pole; to the tropical Latitude of the Great Pacific Ocean; and of the strange things that befell.”

Exploring the “undiscovered” classification is expected to be a boon for enriching the public data portals, Rubin said. He also noted that lurking among these difficult ones may well be the discovery of a “fourth domain” of life, to which a reasonable mariner, ancient or contemporary, may proclaim, “full speed ahead.”

Reference: T. Woyke, E. M. Rubin. Searching for new branches on the tree of life.Science, 2014; 346 (6210): 698 DOI: 10.1126/science.1258871

Landmark study on the evolution of insects

An international team of more than 100 researchers has published the first modern roadmap of insect evolution. Understanding how insects are related uncovers their true ecological, economic, and medical importance, and, until now, has been largely unknown. The unprecedented results reconstruct the insect ‘tree of life’ and answer longstanding questions about the origins and evolution of insects.
 The California Academy of Sciences houses a ten-million-specimen Entomology collection -- one of the largest in North America. The study results published in this week's issue of Science tell Academy researchers more than ever before about the evolution of insects. Scientists now believe insects originated at the same time as the earliest terrestrial plants, about 480 million years ago. Credit: Copyright Andrew McCormick for the California Academy of Sciences


The California Academy of Sciences houses a ten-million-specimen Entomology collection — one of the largest in North America. The study results published in this week’s issue of Science tell Academy researchers more than ever before about the evolution of insects. Scientists now believe insects originated at the same time as the earliest terrestrial plants, about 480 million years ago.
Credit: Copyright Andrew McCormick for the California Academy of Sciences

The results, published by scientists from the 1KITE project (1,000 Insect Transcriptome Evolution,http://www.1kite.org), are essential to understanding the millions of living insect species that shape our terrestrial living space and both support and threaten our natural resources.

“When you imagine a giant map of the evolution of life on Earth, insects are by far the largest part of the picture,” says Trautwein, the Academy curator who contributed to the fly-related portion of the study. “We have not had a very clear picture of how insects evolved–from the origins of metamorphosis to which insects were first to fly. New sequencing technology allowed us to compare huge amounts of genetic data, and for the first time ever, we can fill these knowledge gaps. Science is taking us closer to solving the mysteries of the evolution of life than ever before.”

Using a dataset consisting of 144 carefully chosen species, 1KITE scientists present reliable estimates on the dates of origin and relationships of all major insect groups based on the enormous molecular dataset they collected. They show that insects originated at the same time as the earliest terrestrial plants about 480 million years ago. Their analyses suggests that insects and plants shaped the earliest terrestrial ecosystems together, with insects developing wings to fly 400 million years ago, long before any other animal could do so, and at nearly the same time that land plants first grew substantially upwards to form forests.

“Phylogeny forms the foundation for telling us the who?, what?, when?, and why? of life,” says Dr. Karl Kjer, Professor from Rutgers University. “Many previously intractable questions are now resolved, while many of the “revolutions” brought about by previous analyses of smaller molecular datasets have contained errors that are now being corrected.”

Reference: B. Misof, S. Liu, K. Meusemann, R. S. Peters, A. Donath, C. Mayer, P. B. Frandsen, J. Ware, T. Flouri, R. G. Beutel, O. Niehuis, M. Petersen, F. Izquierdo-Carrasco, T. Wappler, J. Rust, A. J. Aberer, U. Aspock, H. Aspock, D. Bartel, A. Blanke, S. Berger, A. Bohm, T. R. Buckley, B. Calcott, J. Chen, F. Friedrich, M. Fukui, M. Fujita, C. Greve, P. Grobe, S. Gu, Y. Huang, L. S. Jermiin, A. Y. Kawahara, L. Krogmann, M. Kubiak, R. Lanfear, H. Letsch, Y. Li, Z. Li, J. Li, H. Lu, R. Machida, Y. Mashimo, P. Kapli, D. D. McKenna, G. Meng, Y. Nakagaki, J. L. Navarrete-Heredia, M. Ott, Y. Ou, G. Pass, L. Podsiadlowski, H. Pohl, B. M. von Reumont, K. Schutte, K. Sekiya, S. Shimizu, A. Slipinski, A. Stamatakis, W. Song, X. Su, N. U. Szucsich, M. Tan, X. Tan, M. Tang, J. Tang, G. Timelthaler, S. Tomizuka, M. Trautwein, X. Tong, T. Uchifune, M. G. Walzl, B. M. Wiegmann, J. Wilbrandt, B. Wipfler, T. K. F. Wong, Q. Wu, G. Wu, Y. Xie, S. Yang, Q. Yang, D. K. Yeates, K. Yoshizawa, Q. Zhang, R. Zhang, W. Zhang, Y. Zhang, J. Zhao, C. Zhou, L. Zhou, T. Ziesmann, S. Zou, Y. Li, X. Xu, Y. Zhang, H. Yang, J. Wang, J. Wang, K. M. Kjer, X. Zhou. Phylogenomics resolves the timing and pattern of insect evolution. Science, 2014; 346 (6210): 763 DOI: 10.1126/science.1257570

“The Answer is Blowing in the Intergalactic Wind”

Astronomers have provided the first direct evidence that an intergalactic ‘wind’ is stripping galaxies of star-forming gas as they fall into clusters of galaxies. The observations help explain why galaxies found in clusters are known to have relatively little gas and less star formation when compared to non-cluster or ‘field’ galaxies.
A composite image shows the galaxy NGC 4522 in the Virgo Cluster, the nearest large cluster of galaxies to our own local group of galaxies, and the “wake” of gas and dust being blown from the galaxy. The galaxy appears blue in the Hubble Space Telescope image in visible light. The superimposed red image is from Spitzer data and shows emissions from dust that traces molecular hydrogen. In the image, the galaxy is moving down and into the plane of the photo. Credit: Suresh Sivanandam; Dunlap Institute for Astronomy & Astrophysics

A composite image shows the galaxy NGC 4522 in the Virgo Cluster, the nearest large cluster of galaxies to our own local group of galaxies, and the “wake” of gas and dust being blown from the galaxy. The galaxy appears blue in the Hubble Space Telescope image in visible light. The superimposed red image is from Spitzer data and shows emissions from dust that traces molecular hydrogen. In the image, the galaxy is moving down and into the plane of the photo.
Credit: Suresh Sivanandam; Dunlap Institute for Astronomy & Astrophysics

Astronomers have theorized that as a field galaxy falls into a cluster of galaxies, it encounters the cloud of hot gas at the centre of the cluster. As the galaxy moves through this intra-cluster medium at thousands of kilometres per second, the cloud acts like a wind, blowing away the gas within the galaxy without disturbing its stars. The process is known as ram-pressure stripping.

Previously, astronomers had seen the very tenuous atomic hydrogen gas surrounding a galaxy get stripped. But it was believed that the denser molecular hydrogen clouds where stars form would be more resistant to the wind. “However, we found that the molecular hydrogen gas is also blown from the in-falling galaxy,” says Suresh Sivanandam of the Dunlap Institute at the University of Toronto, “much like smoke blown from a candle being carried into a room.”

Previous observations showed indirect evidence of ram-pressure stripping of star-forming gas. Astronomers have observed young stars trailing from a galaxy; the stars would have formed from gas newly-stripped from the galaxy. A few galaxies also have tails of very tenuous gas. But the latest observations show the stripped, molecular hydrogen itself, which can be seen as a wake trailing from the galaxy in the direction opposite to its motion.

The results, published in the Astrophysical Journal on Nov. 10, are from observations of four galaxies. Sivanandam, Rieke and colleague Marcia Rieke (also from the University of Arizona) had already established that one of the four galaxies had been stripped of its star-forming gas by this wind. But by observing four galaxies, they have now shown that this effect is common.

The team made their analysis using optical, infrared and hydrogen-emission data from the Spitzer and Hubble space telescopes, as well as archival ground-based data. The team used an infrared spectrograph on the Spitzer because direct observation of the molecular hydrogen required observations in the mid-infrared part of the spectrum — something that’s almost impossible to do from the ground.

“Seeing this stripped molecular gas is like seeing a theory on display in the sky,” says Marcia Rieke. “Astronomers have assumed that something stopped the star formation in these galaxies, but it is very satisfying to see the actual cause.”

Dunlap Institute for Astronomy & Astrophysics.

Shocking tale of solar system birth

Astrophysicists say that magnetic clues in a meteorite outline the earliest steps in the formation of the solar system and Earth-like planets.
Magnetic field lines (green) weave through the cloud of dusty gas surrounding the newborn Sun. In the foreground are asteroids and chondrules, the building blocks of chondritic meteorites. While solar magnetic fields dominate the region near the Sun, out where the asteroids orbit, chondrules preserve a record of varying local magnetic fields. Credit: Science

Magnetic field lines (green) weave through the cloud of dusty gas surrounding the newborn Sun. In the foreground are asteroids and chondrules, the building blocks of chondritic meteorites. While solar magnetic fields dominate the region near the Sun, out where the asteroids orbit, chondrules preserve a record of varying local magnetic fields.
Credit: Science

The results appear in a paper published Nov. 13 in the journal Science. The lead author is graduate student Roger Fu of MIT, working under Benjamin Weiss; Steve Desch of Arizona State University’s School of Earth and Space Exploration is a co-author of the paper.

“The measurements made by Fu and Weiss are astounding and unprecedented,” says Desch. “Not only have they measured tiny magnetic fields thousands of times weaker than a compass feels, they have mapped the magnetic fields’ variation recorded by the meteorite, millimeter by millimeter.”

Construction debris

It may seem all but impossible to determine how the solar system formed, given it happened about 4.5 billion years ago. But making the solar system was a messy process, leaving lots of construction debris behind for scientists to study.

Among the most useful pieces of debris are the oldest, most primitive and least altered type of meteorites, called the chondrites (KON-drites). Chondrite meteorites are pieces of asteroids, broken off by collisions, that have remained relatively unmodified since they formed at the birth of the solar system. They are built mostly of small stony grains, called chondrules, barely a millimeter in diameter.

Chondrules themselves formed through quick melting events in the dusty gas cloud — the solar nebula — that surrounded the young sun. Patches of the solar nebula must have been heated above the melting point of rock for hours to days. Dustballs caught in these events made droplets of molten rock, which then cooled and crystallized into chondrules.

Tiny magnets

As chondrules cooled, iron-bearing minerals within them became magnetized like bits on a hard drive by the local magnetic field in the gas. These magnetic fields are preserved in the chondrules even down to the present day.

The chondrule grains whose magnetic fields were mapped in the new study came from a meteorite named Semarkona, after the place in India where it fell in 1940. It weighed 691 grams, or about a pound and a half.

The scientists focused specifically on the embedded magnetic fields captured by “dusty” olivine grains that contain abundant iron-bearing minerals. These had a magnetic field of about 54 microtesla, similar to the magnetic field at Earth’s surface, which ranges from 25 to 65 microtesla.

Coincidentally, many previous measurements of meteorites also implied similar field strengths. But it is now understood that those measurements detected magnetic minerals contaminated by Earth’s magnetic field, or even from hand magnets used by meteorite collectors.

“The new experiments,” Desch says, “probe magnetic minerals in chondrules never measured before. They also show that each chondrule is magnetized like a little bar magnet, but with ‘north’ pointing in random directions.”

This shows, he says, they became magnetized before they were built into the meteorite, and not while sitting on Earth’s surface.

Shocks and more shocks

“My modeling for the heating events shows that shock waves passing through the solar nebula is what melted most chondrules,” Desch explains. Depending on the strength and size of the shock wave, the background magnetic field could be amplified by up to 30 times.

He says, “Given the measured magnetic field strength of about 54 microtesla, this shows the background field in the nebula was probably in the range of 5 to 50 microtesla.”

There are other ideas for how chondrules might have formed, some involving magnetic flares above the solar nebula, or passage through the sun’s magnetic field. But those mechanisms require stronger magnetic fields than what is measured in the Semarkona samples.

This reinforces the idea that shocks melted the chondrules in the solar nebula at about the location of today’s asteroid belt, which lies some two to four times farther from the sun than Earth now orbits.

Desch says, “This is the first really accurate and reliable measurement of the magnetic field in the gas from which our planets formed.”

Reference: Roger R. Fu, Benjamin P. Weiss, Eduardo A. Lima, Richard J. Harrison, Xue-Ning Bai, Steven J. Desch, Denton S. Ebel, Clement Suavet, Huapei Wang, David Glenn, David Le Sage, Takeshi Kasama, Ronald L. Walsworth, and Aaron T. Kuan.Solar nebula magnetic fields recorded in the Semarkona meteorite. Science, 13 November 2014 DOI: 10.1126/science.1258022

Arizona State University

Birth of planets revealed in astonishing detail in ALMA’s ‘best image ever’

Astronomers have captured the best image ever of planet formation around an infant star as part of the testing and verification process for the Atacama Large Millimeter/submillimeter Array’s (ALMA) new high-resolution capabilities.

This revolutionary new image reveals in astonishing detail the planet-forming disk surrounding HL Tau, a Sun-like star located approximately 450 light-years from Earth in the constellation Taurus.

ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star.

ALMA image of the young star HL Tau and its protoplanetary disk. This best image ever of planet formation reveals multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF)

ALMA image of the young star HL Tau and its protoplanetary disk. This best image ever of planet formation reveals multiple rings and gaps that herald the presence of emerging planets as they sweep their orbits clear of dust and gas. Credit: ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF)

“These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.

All stars are believed to form within clouds of gas and dust that collapse under gravity. Over time, the surrounding dust particles stick together, growing into sand, pebbles, and larger-size rocks, which eventually settle into a thin protoplanetary disk where asteroids, comets, and planets form.

Once these planetary bodies acquire enough mass, they dramatically reshape the structure of their natal disk, fashioning rings and gaps as the planets sweep their orbits clear of debris and shepherd dust and gas into tighter and more confined zones.

The new ALMA image reveals these striking features in exquisite detail, providing the clearest picture to date of planet formation. Images with this level of detail were previously only seen in computer models and artist concepts. ALMA, living up to its promise, has now provided direct proof that nature and theory are very much in agreement.

“This new and unexpected result provides an incredible view of the process of planet formation. Such clarity is essential to understand how our own Solar System came to be and how planets form throughout the Universe,” said Tony Beasley, director of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, which manages ALMA operations for astronomers in North America.

HL Tau is hidden in visible light behind a massive envelope of dust and gas. Since ALMA observes at much longer wavelengths, it is able to peer through the intervening dust to study the processes right at the core of this cloud. “This is truly one of the most remarkable images ever seen at these wavelengths. The level of detail is so exquisite that it’s even more impressive than many optical images. The fact that we can see planets being born will help us understand not only how planets form around other stars but also the origin of our own Solar System,” said NRAO astronomer Crystal Brogan.

ALMA’s new high-resolution capabilities were achieved by spacing the antennas up to 15 kilometers apart. This baseline at millimeter wavelengths enabled a resolution of 35 milliarcseconds, which is equivalent to a penny as seen from more than 110 kilometers away.

“Such a resolution can only be achieved with the long baseline capabilities of ALMA and provides astronomers with new information that is impossible to collect with any other facility, including the best optical observatories,” noted ALMA Director Pierre Cox.

These long baselines fulfill one of ALMA’s major objectives and mark an impressive technological and engineering milestone. Future observations at ALMA’s longest possible baseline of 16 kilometers will produce even clearer images and continue to expand our understanding of the cosmos.

“This observation illustrates the dramatic and important results that come from NSF supporting world-class instrumentation such as ALMA,” said Fleming Crim, the National Science Foundation assistant director for Mathematical and Physical Sciences. “ALMA is delivering on its enormous potential for revealing the distant Universe and is playing a unique and transformational role in astronomy.”

SourceNational Radio Astronomy Observatory

Ancient DNA shows earliest European genomes weathered the Ice Age

A genome taken from a 36,000 skeleton reveals an early divergence of Eurasians once they had left Africa, and allows scientists to better assess the point at which ‘admixture’ — or interbreeding — between Eurasians and Neanderthals occurred. The latest research also points to a previously unknown population lineage as old as the first population separations since humans dispersed out of Africa.
This is an image of the Kostenki skull fossil. Credit: Peter the Great Museum

This is an image of the Kostenki skull fossil.
Credit: Peter the Great Museum

The study also uncovers a more accurate timescale for when humans and Neanderthals interbred, and finds evidence for an early contact between the European hunter-gatherers and those in the Middle East — who would later develop agriculture and disperse into Europe about 8,000 years ago, transforming the European gene pool.

Scientists now believe Eurasians separated into at least three populations earlier than 36,000 years ago: Western Eurasians, East Asians and a mystery third lineage, all of whose descendants would develop the unique features of most non-African peoples — but not before some interbreeding with Neanderthals took place.

Led by the Centre for GeoGenetics at the University of Copenhagen, the study was conducted by an international team of researchers from institutions including the University of Cambridge’s Departments of Archaeology and Anthropology, and Zoology, and is published today in the journal Science.

By cross-referencing the ancient man’s complete genome — the second oldest modern human genome ever sequenced — with previous research, the team discovered a surprising genetic “unity” running from the first modern humans in Europe, suggesting that a ‘meta-population’ of Palaeolithic hunter-gatherers with deep shared ancestry managed to survive through the Last Glacial Maximum and colonise the landmass of Europe for more than 30,000 years.

While the communities within this overarching population expanded, mixed and fragmented during seismic cultural shifts and ferocious climate change, this was a “reshuffling of the same genetic deck” say scientists, and European populations as a whole maintained the same genetic thread from their earliest establishment out of Africa until Middle Eastern populations arrived in the last 8,000 years, bringing with them agriculture and lighter skin colour.

“That there was continuity from the earliest Upper Palaeolithic to the Mesolithic, across a major glaciation, is a great insight into the evolutionary processes underlying human success,” said co-author Dr Marta Mirazón Lahr, from Cambridge’s Leverhulme Centre for Human Evolutionary Studies (LCHES).

“For 30,000 years ice sheets came and went, at one point covering two-thirds of Europe. Old cultures died and new ones emerged — such as the Aurignacian and the Grevettian — over thousands of years, and the hunter-gatherer populations ebbed and flowed. But we now know that no new sets of genes are coming in: these changes in survival and cultural kit are overlaid on the same biological background,” Mirazón Lahr said. “It is only when famers from the Near East arrived about 8,000 years ago that the structure of the European population changed significantly.”

The Kostenki genome also contained, as with all people of Eurasia today, a small percentage of Neanderthal genes, confirming previous findings which show there was an ‘admixture event’ early in the human colonisation Eurasia: a period when Neanderthals and the first humans to leave Africa for Europe briefly interbred.

The new study allows scientists to closer estimate this ‘event’ as occurring around 54,000 years ago, before the Eurasian population began to separate. This means that, even today, anyone with a Eurasian ancestry — from Chinese to Scandinavian and North American — has a small element of Neanderthal DNA.

However, despite Western Eurasians going on to share the European landmass with Neanderthals for another 10,000 years, no further periods of interbreeding occurred.

“Were Neanderthal populations dwindling very fast? Did modern humans still encounter them? We were originally surprised to discover there had been interbreeding. Now the question is, why so little? It’s an extraordinary finding that we don’t understand yet,” said co-author Professor Robert Foley, also from LCHES.

Unique to the Kostenki genome is a small element it shares with people who live in parts of the Middle East now, and who were also the population of farmers that arrived in Europe about 8,000 years ago and assimilated with indigenous hunter-gatherers. This early contact is surprising, and provides the first clues to a hereto unknown lineage that could be as old as — or older than — the other major Eurasian genetic lines. These two populations must have interacted briefly before 36,000 years ago, and then remained isolated from each other for tens of millennia.

“This element of the Kostenki genome confirms the presence of a yet unmapped major population lineage in Eurasia. The population separated early on from ancestors of other Eurasians, both Europeans and Eastern Asians,” said Andaine Seguin-Orlando from the Centre for GeoGenetics in Copenhagen.

Mirazón Lahr points out that, while Western Eurasia was busy mixing as a ‘meta-population’, there was no interbreeding with these mystery populations for some 30,000 years — meaning there must have been some kind of geographic barrier for millennia, despite the fact that Europe and the Middle East seem, for us at least, to be so close geographically. But the Kostenki genome not only shows the existence of these unmapped populations, but that there was at least one window of time when whatever barrier existed became briefly permeable.

“This mystery population may have remained small for a very long time, surviving in refugia in areas such as the Zagros Mountains of Iran and Iraq, for example,” said Mirazón Lahr. “We have no idea at the moment where they were for those first 30,000 years, only that they were in the Middle East by the end of the ice age, when they invented agriculture.”

Lead author and Lundbeck Foundation Professor Eske Willerslev added: “This work reveals the complex web of population relationships in the past, generating for the first time a firm framework with which to explore how humans responded to climate change, encounters with other populations, and the dynamic landscapes of the ice age.”

Source: Cambridge University, Research section LINK

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