̽��ֱ�� of Cambridge - Trinity College Dublin

Scientists reveal structure of 74 exocomet belts orbiting nearby stars

Anonymous — Fri, 17 Jan 2025 08:00:00 +0000

̽��ֱ��crystal-clear images show light being emitted from these millimetre-sized pebbles within the belts that orbit 74 nearby stars of a wide variety of ages – from those that are just emerging to those in more mature systems like our own Solar System.

̽��ֱ��REASONS (REsolved ALMA and SMA Observations of Nearby Stars) study, led by Trinity College Dublin and involving researchers from the ̽��ֱ�� of Cambridge, is a milestone in the study of exocometary belts because its images and analyses reveal where the pebbles, and the exocomets, are located. They are typically tens to hundreds of astronomical units (the distance from Earth to the Sun) from their central star.

In these regions, it is so cold (-250 to -150 degrees Celsius) that most compounds are frozen as ice on the exocomets. What the researchers are therefore observing is where the ice reservoirs of planetary systems are located. REASONS is the first programme to unveil the structure of these belts for a large sample of 74 exoplanetary systems. ̽��ֱ��results are reported in the journal Astronomy & Astrophysics.

This study used both the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and the Submillimeter Array (SMA) in Hawai‘i to produce the images that have provided more information on populations of exocomets than ever before. Both telescope arrays observe electromagnetic radiation at millimetre and submillimetre wavelengths.

“Exocomets are boulders of rock and ice, at least one kilometre in size, which smash together within these belts to produce the pebbles that we observe here with the ALMA and SMA arrays of telescopes,” said lead author Luca Matrà from Trinity College Dublin. “Exocometary belts are found in at least 20% of planetary systems, including our own Solar System.”

“ ̽��ֱ��images reveal a remarkable diversity in the structure of belts,” said co-author Dr Sebastián Marino from the ̽��ֱ�� of Exeter. “Some are narrow rings, as in the canonical picture of a ‘belt’ like our Solar System’s Edgeworth-Kuiper belt. But a larger number of them are wide, and probably better described as ‘disks’ rather than rings.”

Some systems have multiple rings/disks, some of which are eccentric, providing evidence that yet undetectable planets are present and their gravity affects the distribution of pebbles in these systems.

“ ̽��ֱ��power of a large study like REASONS is in revealing population-wide properties and trends,” said Matrà.

For example, the study confirmed that the number of pebbles decreases for older planetary systems as belts run out of larger exocomets smashing together, but showed for the first time that this decrease in pebbles is faster if the belt is closer to the central star. It also indirectly showed – through the belts’ vertical thickness – that objects as large as 140 km across and even Moon-size objects are likely present in these belts.

“We have been studying exocometary belts for decades, but until now only a handful had been imaged,” said co-author Professor Mark Wyatt from Cambridge’s Institute of Astronomy. “This is the largest collection of such images and demonstrates that we already have the capabilities to probe the structures of the planetary systems orbiting a large fraction of the stars near to the Sun.”

“Arrays like the ALMA and SMA used in this work are extraordinary tools that are continuing to give us incredible new insights into the universe and its workings,” said co-author Dr David Wilner from the Center for Astrophysics | Harvard & Smithsonian “ ̽��ֱ��REASONS survey required a large community effort and has an incredible legacy value, with multiple potential pathways for future investigation.”

Reference:
L. Matrà et al. ‘REsolved ALMA and SMA Observations of Nearby Stars. REASONS: A population of 74 resolved planetesimal belts at millimetre wavelengths.’ Astronomy & Astrophysics (2025). DOI: 10.1051/0004-6361/202451397

Adapted from a Trinity College Dublin media release.

An international team of astrophysicists has imaged a large number of exocomet belts around nearby stars, and the tiny pebbles within them.

Luca Matra, Trinity College Dublin, and colleagues

Millimetre continuum images for the REASONS resolved sample of 74 exocomet belts

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Why reading nursery rhymes and singing to babies may help them to learn language

cg605 — Thu, 30 Nov 2023 16:53:12 +0000

Parents should speak to their babies using sing-song speech, like nursery rhymes, as soon as possible, say researchers. That’s because babies learn languages from rhythmic information, not phonetic information, in their first months.

Phonetic information – the smallest sound elements of speech, typically represented by the alphabet – is considered by many linguists to be the foundation of language. Infants are thought to learn these small sound elements and add them together to make words. But a new study suggests that phonetic information is learnt too late and slowly for this to be the case.

Instead, rhythmic speech helps babies learn language by emphasising the boundaries of individual words and is effective even in the first months of life.

Researchers from the ̽��ֱ�� of Cambridge and Trinity College Dublin investigated babies’ ability to process phonetic information during their first year.

Their study, published today in the journal Nature Communications, found that phonetic information wasn’t successfully encoded until seven months old, and was still sparse at 11 months old when babies began to say their first words.

“Our research shows that the individual sounds of speech are not processed reliably until around seven months, even though most infants can recognise familiar words like ‘bottle’ by this point,” said Cambridge neuroscientist, Professor Usha Goswami. “From then individual speech sounds are still added in very slowly – too slowly to form the basis of language.”

̽��ֱ��researchers recorded patterns of electrical brain activity in 50 infants at four, seven and eleven months old as they watched a video of a primary school teacher singing 18 nursery rhymes to an infant. Low frequency bands of brainwaves were fed through a special algorithm, which produced a ‘read out’ of the phonological information that was being encoded.

̽��ֱ��researchers found that phonetic encoding in babies emerged gradually over the first year of life, beginning with labial sounds (e.g. b for “baby”) and nasal sounds (e.g. m for “mummy”), with the ‘read out’ progressively looking more like that of adults

First author, Professor Giovanni Di Liberto, a cognitive and computer scientist at Trinity College Dublin and a researcher at the ADAPT Centre, said: “This is the first evidence we have of how brain activity relates to phonetic information changes over time in response to continuous speech.”

Previously, studies have relied on comparing the responses to nonsense syllables, like “bif” and “bof” instead.

̽��ֱ��current study forms part of the BabyRhythm project led by Goswami, which is investigating how language is learnt and how this is related to dyslexia and developmental language disorder.

Goswami believes that it is rhythmic information – the stress or emphasis on different syllables of words and the rise and fall of tone – that is the key to language learning. A sister study, also part of the BabyRhythm project, has shown that rhythmic speech information was processed by babies at two months old – and individual differences predicted later language outcomes. ̽��ֱ��experiment was also conducted with adults who showed an identical ‘read out’ of rhythm and syllables to babies.

“We believe that speech rhythm information is the hidden glue underpinning the development of a well-functioning language system,” said Goswami. “Infants can use rhythmic information like a scaffold or skeleton to add phonetic information on to. For example, they might learn that the rhythm pattern of English words is typically strong-weak, as in ‘daddy’ or ‘mummy’, with the stress on the first syllable. They can use this rhythm pattern to guess where one word ends and another begins when listening to natural speech.”

“Parents should talk and sing to their babies as much as possible or use infant directed speech like nursery rhymes because it will make a difference to language outcome,” she added.

Goswami explained that rhythm is a universal aspect of every language all over the world. “In all language that babies are exposed to there is a strong beat structure with a strong syllable twice a second. We’re biologically programmed to emphasise this when speaking to babies.”

Goswami says that there is a long history in trying to explain dyslexia and developmental language disorder in terms of phonetic problems but that the evidence doesn’t add up. She believes that individual differences in children’s language originate with rhythm.

̽��ֱ��research was funded by the European Research Council under the European Union’s Horizon 2020 research and innovation programme and by Science Foundation Ireland.

More on this research

Di Liberto et al. Emergence of the cortical encoding of phonetic features in the first year of life, Nature Communications DOI: 10.1038/s41467-023-43490-x

Researchers find that babies don’t begin to process phonetic information reliably until seven months old which they say is too late to form the foundation of language.

This is the first evidence we have of how brain activity relates to phonetic information changes over time in response to continuous speech.

Professor Giovanni Di Liberto

Centre for Neuroscience in Education, ̽��ֱ�� of Cambridge

Babies wearing 'head cap' to measure electrical brain activity

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Liquid water beneath Martian polar ice cap

sc604 — Thu, 29 Sep 2022 14:38:08 +0000

An international team of researchers has revealed new evidence for the possible existence of liquid water beneath the south polar ice cap of Mars.

Baltic hunter-gatherers adopted farming without influence of mass migration, ancient DNA suggests

fpjl2 — Thu, 02 Feb 2017 17:18:30 +0000

New research indicates that Baltic hunter-gatherers were not swamped by migrations of early agriculturalists from the Middle East, as was the case for the rest of central and western Europe. Instead, these people probably acquired knowledge of farming and ceramics by sharing cultures and ideas rather than genes with outside communities.

Scientists extracted ancient DNA from a number of archaeological remains discovered in Latvia and the Ukraine, which were between 5,000 and 8,000 years old. These samples spanned the Neolithic period, which was the dawn of agriculture in Europe, when people moved from a mobile hunter-gatherer lifestyle to a settled way of life based on food production.

We know through previous research that large numbers of early farmers from the Levant (the Near East) – driven by the success of their technological innovations such as crops and pottery – had expanded to the peripheral parts of Europe by the end of the Neolithic and largely replaced hunter-gatherer populations.

However, the new study, published today in the journal Current Biology, shows that the Levantine farmers did not contribute to hunter-gatherers in the Baltic as they did in Central and Western Europe.

̽��ֱ��research team, which includes scientists from the ̽��ֱ�� of Cambridge and Trinity College Dublin, say their findings instead suggest that the Baltic hunter-gatherers learned these skills through communication and cultural exchange with outsiders.

̽��ֱ��findings feed into debates around the ‘Neolithic package’ – the cluster of technologies such as domesticated livestock, cultivated cereals and ceramics, which revolutionised human existence across Europe during the late Stone Age.

Advances in ancient DNA work have revealed that this ‘package’ was spread through Central and Western Europe by migration and interbreeding: the Levant and later Anatolian farmers mixing with and essentially replacing the hunter-gatherers.

But the new work suggests migration was not a ‘universal driver’ across Europe for this way of life. In the Baltic region, archaeology shows that the technologies of the ‘package’ did develop – albeit less rapidly – even though the analyses show that the genetics of these populations remained the same as those of the hunter-gatherers throughout the Neolithic.

Andrea Manica, one of the study’s senior authors from the ̽��ֱ�� of Cambridge, said: “Almost all ancient DNA research up to now has suggested that technologies such as agriculture spread through people migrating and settling in new areas.”

“However, in the Baltic, we find a very different picture, as there are no genetic traces of the farmers from the Levant and Anatolia who transmitted agriculture across the rest of Europe.”

“ ̽��ֱ��findings suggest that indigenous hunter-gatherers adopted Neolithic ways of life through trade and contact, rather than being settled by external communities. Migrations are not the only model for technology acquisition in European prehistory.”

̽��ֱ��researchers analysed eight ancient genomes – six from Latvia and two from Ukraine – that spanned a timeframe of three and a half thousand years (between 8,300 and 4,800 years ago). This enabled them to start plotting the genetic history of Baltic inhabitants during the Neolithic.

DNA was extracted from the petrous area of skulls that had been recovered by archaeologists from some of the region’s richest Stone Age cemeteries. ̽��ֱ��petrous, at the base of the skull, is one of the densest bones in the body, and a prime location for DNA that has suffered the least contamination over millennia.

While the sequenced genomes showed no trace of the Levant farmer influence, one of the Latvian samples did reveal genetic influence from a different external source – one that the scientists say could be a migration from the Pontic Steppe in the east. ̽��ֱ��timing (5-7,000 years ago) fits with previous research estimating the earliest Slavic languages.

Researcher Eppie Jones, from Trinity College Dublin and the ̽��ֱ�� of Cambridge, was the lead author of the study. She said: “There are two major theories on the spread of Indo-European languages, the most widely spoken language family in the world. One is that they came from the Anatolia with the agriculturalists; another that they developed in the Steppes and spread at the start of the Bronze Age.

“That we see no farmer-related genetic input, yet we do find this Steppe-related component, suggests that at least the Balto-Slavic branch of the Indo-European language family originated in the Steppe grasslands of the East, which would bring later migrations of Bronze Age horse riders.”

̽��ֱ��researchers point out that the time scales seen in Baltic archaeology are also very distinct to the rest of Europe, with a much more drawn-out and piecemeal uptake of Neolithic technologies, rather than the complete ‘package’ that arrives with migrations to take most of Europe by storm.

Andrea Manica added: “Our evidence of genetic continuity in the Baltic, coupled with the archaeological record showing a prolonged adoption of Neolithic technologies, would suggest the existence of trade networks with farming communities largely independent of interbreeding.

“It seems the hunter-gatherers of the Baltic likely acquired bits of the Neolithic package slowly over time through a ‘cultural diffusion’ of communication and trade, as there is no sign of the migratory wave that brought farming to the rest of Europe during this time.

“ ̽��ֱ��Baltic hunter-gatherer genome remains remarkably untouched until the great migrations of the Bronze Age sweep in from the East.”

Ancient DNA analyses show that – unlike elsewhere in Europe – farmers from the Near East did not overtake hunter-gatherer populations in the Baltic. The findings also suggest that the Balto-Slavic branch of the Indo-European language family originated in the Steppe grasslands of the East.

̽��ֱ��Baltic hunter-gatherer genome remains remarkably untouched until the great migrations of the Bronze Age sweep in from the East

Andrea Manica

Valters Grivins

̽��ֱ��shores of Lake Burtnieks in Latvia, near where the human remains were discovered from which ancient DNA was extracted for this study.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Ancient DNA reveals 'genetic continuity’ between Stone Age and modern populations in East Asia

fpjl2 — Wed, 01 Feb 2017 19:04:57 +0000

Researchers working on ancient DNA extracted from human remains interred almost 8,000 years ago in a cave in the Russian Far East have found that the genetic makeup of certain modern East Asian populations closely resemble that of their hunter-gatherer ancestors.

̽��ֱ��study, published today in the journal Science Advances, is the first to obtain nuclear genome data from ancient mainland East Asia and compare the results to modern populations.

̽��ֱ��findings indicate that there was no major migratory interruption, or “population turnover”, for well over seven millennia. Consequently, some contemporary ethnic groups share a remarkable genetic similarity to Stone Age hunters that once roamed the same region.

̽��ֱ��high “genetic continuity” in East Asia is in stark contrast to most of Western Europe, where sustained migrations of early farmers from the Levant overwhelmed hunter-gatherer populations. This was followed by a wave of horse riders from Central Asia during the Bronze Age. These events were likely driven by the success of emerging technologies such as agriculture and metallurgy

̽��ֱ��new research shows that, at least for part of East Asia, the story differs – with little genetic disruption in populations since the early Neolithic period.

Despite being separated by a vast expanse of history, this has allowed an exceptional genetic proximity between the Ulchi people of the Amur Basin, near where Russia borders China and North Korea, and the ancient hunter-gatherers laid to rest in a cave close to the Ulchi’s native land.

̽��ֱ��researchers suggest that the sheer scale of East Asia and dramatic variations in its climate may have prevented the sweeping influence of Neolithic agriculture and the accompanying migrations that replaced hunter-gatherers across much of Europe. They note that the Ulchi retained their hunter-fisher-gatherer lifestyle until recent times.

“Genetically speaking, the populations across northern East Asia have changed very little for around eight millennia,” said senior author Andrea Manica from the ̽��ֱ�� of Cambridge, who conducted the work with an international team, including colleagues from Ulsan National Institute of Science and Technology in Korea, and Trinity College Dublin and ̽��ֱ�� College Dublin in Ireland.

“Once we accounted for some local intermingling, the Ulchi and the ancient hunter-gatherers appeared to be almost the same population from a genetic point of view, even though there are thousands of years between them.”

̽��ֱ��new study also provides further support for the ‘dual origin’ theory of modern Japanese populations: that they descend from a combination of hunter-gatherers and agriculturalists that eventually brought wet rice farming from southern China. A similar pattern is also found in neighbouring Koreans, who are genetically very close to Japanese.

However, Manica says that much more DNA data from Neolithic China is required to pinpoint the origin of the agriculturalists involved in this mixture.

̽��ֱ��team from Trinity College Dublin were responsible for extracting DNA from the remains, which were found in a cave known as Devil’s Gate. Situated in a mountainous area close to the far eastern coast of Russia that faces northern Japan, the cave was first excavated by a soviet team in 1973.

Along with hundreds of stone and bone tools, the carbonised wood of a former dwelling, and woven wild grass that is one of the earliest examples of a textile, were the incomplete bodies of five humans.

If ancient DNA can be found in sufficiently preserved remains, sequencing it involves sifting through the contamination of millennia. ̽��ֱ��best samples for analysis from Devil’s Gate were obtained from the skulls of two females: one in her early twenties, the other close to fifty. ̽��ֱ��site itself dates back over 9,000 years, but the two women are estimated to have died around 7,700 years ago.

Researchers were able to glean the most from the middle-aged woman. Her DNA revealed she likely had brown eyes and thick, straight hair. She almost certainly lacked the ability to tolerate lactose, but was unlikely to have suffered from ‘alcohol flush’: the skin reaction to alcohol now common across East Asia.

While the Devil’s Gate samples show high genetic affinity to the Ulchi, fishermen from the same area who speak the Tungusic language, they are also close to other Tungusic-speaking populations in present day China, such as the Oroqen and Hezhen.

“These are ethnic groups with traditional societies and deep roots across eastern Russia and China, whose culture, language and populations are rapidly dwindling,” added lead author Veronika Siska, also from Cambridge.

“Our work suggests that these groups form a strong genetic lineage descending directly from the early Neolithic hunter-gatherers who inhabited the same region thousands of years previously.”

In contrast to Western Europeans, new research finds contemporary East Asians are genetically much closer to the ancient hunter-gatherers that lived in the same region eight thousand years previously.

̽��ֱ��Ulchi and the ancient hunter-gatherers appeared to be almost the same population from a genetic point of view, even though there are thousands of years between them

Andrea Manica

Elizaveta Veselovskaya/Yuriy Chernyavskiy

Right: Exterior of Devil’s Gate, the cave in the Primorye region near the far eastern coast of Russia. Left: One of the skulls found in the Devil’s Gate cave from which ancient DNA used in the study was extracted.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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

fpjl2 — Mon, 16 Nov 2015 10:33:13 +0000

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Inset image: the view from the Satsurblia cave in Western Georgia, where a human right temporal bone dating from over 13,000 years ago was discovered. DNA extracted from this bone was used in the new research.

Reference:
E.R. Jones et. al. ‘Upper Palaeolithic genomes reveal deep roots of modern Eurasians.’ Nature Communications (2015). DOI: 10.1038/ncomms9912

Populations of hunter-gatherers weathered Ice Age in apparent isolation in Caucasus mountain region for millennia, later mixing with other ancestral populations, from which emerged the Yamnaya culture that would bring this Caucasus hunter-gatherer lineage to Western Europe.

This Caucasus pocket is the fourth major strand of ancient European ancestry, one that we were unaware of until now

Andrea Manica

Eppie Jones

DNA was extracted from the molar teeth of this skeleton, dating from almost 10,000 years ago and found in the Kotias Klde rockshelter in Western Georgia.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Ancient genome from Africa sequenced for the first time

fpjl2 — Thu, 08 Oct 2015 18:05:25 +0000

Note: This article was amended on 3 February 2016 following the discovery of a bioinformatics error, and an Erratum issued by the researchers.

̽��ֱ��first ancient human genome from Africa to be sequenced has revealed that a wave of migration back into Africa from Western Eurasia around 3,000 years ago affected the genetic make-up of populations across East Africa.

̽��ֱ��genome was taken from the skull of a man buried face-down 4,500 years ago in a cave called Mota in the highlands of Ethiopia – a cave cool and dry enough to preserve his DNA for thousands of years. Previously, ancient genome analysis has been limited to samples from northern and arctic regions.

̽��ֱ��latest study is the first time an ancient human genome has been recovered and sequenced from Africa, the source of all human genetic diversity. ̽��ֱ��findings are published today in the journal Science.

̽��ֱ��ancient genome predates a mysterious migratory event which occurred roughly 3,000 years ago, known as the ‘Eurasian backflow’, when people from regions of Western Eurasia such as the Near East and Anatolia suddenly flooded back into the Horn of Africa.

̽��ֱ��genome enabled researchers to run a millennia-spanning genetic comparison and determine that these Western Eurasians were closely related to the Early Neolithic farmers who had brought agriculture to Europe 4,000 years earlier.

By comparing the ancient genome to DNA from modern Africans, the team have been able to show that East African populations today have as much as 25% Eurasian ancestry from this event.

Researchers describe the findings as evidence that the ‘backflow’ event was of greater size and influence than previously thought. ̽��ֱ��massive wave of migration was perhaps equivalent to over a quarter of the then population of the Horn of Africa, which hit the area and then dispersed genetically across the north east part of the continent.

“Roughly speaking, the wave of West Eurasian migration back into the Horn of Africa could have been as much as 25% of the population that already lived there – and that, to me, is mind-blowing. ̽��ֱ��question is: what got them moving all of a sudden?” said Dr Andrea Manica, senior author of the study from the ̽��ֱ�� of Cambridge’s Department of Zoology.

Previous work on ancient genetics in Africa had involved trying to work back through the genomes of current populations, attempting to eliminate modern influences. “With an ancient genome, we have a direct window into the distant past. One genome from one individual can provide a picture of an entire population,” said Manica.

̽��ֱ��cause of the West Eurasian migration back into Africa is currently a mystery, with no obvious climatic reasons. Archaeological evidence does, however, show the migration coincided with the arrival of Near Eastern crops into East Africa such as wheat and barley, suggesting the migrants helped develop new forms of agriculture in the region.

̽��ֱ��researchers say it’s clear that the Eurasian migrants were direct descendants of, or a very close population to, the Neolithic farmers that had had brought agriculture from the Near East into West Eurasia around 7,000 years ago, and then migrated into the Horn of Africa some 4,000 years later. “It’s quite remarkable that genetically-speaking this is the same population that left the Near East several millennia previously,” said Eppie Jones, a geneticist at Trinity College Dublin who led the laboratory work to sequence the genome.

While the genetic make-up of the Near East has changed completely over the last few thousand years, the closest modern equivalents to these Neolithic migrants are Sardinians, probably because Sardinia is an isolated island, says Jones. “ ̽��ֱ��famers found their way to Sardinia and created a bit of a time capsule. Sardinian ancestry is closest to the ancient Near East.”

View looking out from the Mota cave in the Ethiopian highlands

“Africa is a total melting pot. We know that the last 3,000 years saw a complete scrambling of population genetics in Africa. So being able to get a snapshot from before these migration events occurred is a big step,” said Marcos Gallego Llorente, first author of the study, also from Cambridge’s Zoology Department.

̽��ֱ��ancient Mota genome allows researchers to jump to before another major African migration: the Bantu expansion, when speakers of an early Bantu language flowed out of West Africa and into central and southern areas around 3,000 years ago. Manica says the Bantu expansion may well have helped carry the Eurasian genomes across eastern Africa.

̽��ֱ��researchers also identified genetic adaptations for living at altitude, and a lack of genes for lactose tolerance – all genetic traits shared by the current populations of the Ethiopian highlands. In fact, the researchers found that modern inhabitants of the area highlands are direct descendants of the Mota man.

Finding high-quality ancient DNA involves a lot of luck, says Dr Ron Pinhasi, co-senior author from ̽��ֱ�� College Dublin. “It’s hard to get your hands on remains that have been suitably preserved. ̽��ֱ��denser the bone, the more likely you are to find DNA that’s been protected from degradation, so teeth are often used, but we found an even better bone – the petrous.” ̽��ֱ��petrous bone is a thick part of the temporal bone at the base of the skull, just behind the ear.

“ ̽��ֱ��sequencing of ancient genomes is still so new, and it’s changing the way we reconstruct human origins,” added Manica. “These new techniques will keep evolving, enabling us to gain an ever-clearer understanding of who our earliest ancestors were.”

̽��ֱ��study was conducted by an international team of researchers, with permission from the Ethiopia’s Ministry of Culture and Authority for Research and Conservation of Cultural Heritage.

DNA from 4,500-year-old Ethiopian skull reveals a large migratory wave of West Eurasians into the Horn of Africa around 3,000 years ago had a genetic impact on modern populations across East Africa.

̽��ֱ��sequencing of ancient genomes is still so new, and it’s changing the way we reconstruct human origins

Andrea Manica

Matthew Curtis

Archaeologists outside the entrance to the Mota cave in the Ethiopian highlands, where the remains containing the ancient genome were discovered.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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