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By comparing the genes of current-day North and South Americans with African and European populations, an Oxford University study has found the genetic fingerprints of the slave trade and colonization that shaped migrations to the Americas hundreds of years ago.

The study published in Nature Communications found that:

• While Spaniards provide the majority of European ancestry in continental American Hispanic/Latino populations, the most common European genetic source in African-Americans and Barbadians comes from Great Britain.

• The Basques, a distinct ethnic group spread across current-day Spain and France, provided a small but distinct genetic contribution to current-day Continental South American populations, including the Maya in Mexico.

• The Caribbean Islands of Puerto Rico and the Dominican Republic are genetically similar to each other and distinct from the other populations, probably reflecting a different migration pattern between the Caribbean and mainland America.

• Compared to South Americans, people from Caribbean countries (such as the Barbados) had a larger genetic contribution from Africa.

• The ancestors of current-day Yoruba people from West Africa (one of the largest African ethnic groups) provided the largest contribution of genes from Africa to all current-day American populations.

• The proportion of African ancestry varied across the continent, from virtually zero (in the Maya people from Mexico) to 87% in current-day Barbados.

• South Italy and Sicily also provided a significant European genetic contribution to Colombia and Puerto Rico, in line with the known history of Italian emigrants to the Americas in the late 19th and early 20th century.

• One of the African-American groups from the USA had French ancestry, in agreement with historical French immigration into the colonial Southern United States.

• The proportion of genes from European versus African sources varied greatly from individual to individual within recipient populations.

'We found that the genetic profile of Americans is much more complex than previously thought,' said study leader Professor Cristian Capelli from the Department of Zoology.

The research team analysed DNA samples collected from people in Barbados, Columbia, the Dominican Republic, Ecuador, Mexico, Puerto Rico and African-Americans in the USA.

They used a technique called haplotype-based analysis to compare the pattern of genes in these 'recipient populations' to 'donor populations' in areas where migrants to America came from.

'We firstly grouped subsets of people in Africa and Europe who were genetically similar and used this fine scale resolution to find which combinations of these clusters resulted in the sort of mixtures that we now see in people across the Americas', said the study's first author, Dr Francesco Montinaro from the Department of Zoology.

'We can see the huge genetic impact that the slave trade had on American populations and our data match historical records', said study author Dr Garrett Hellenthal from the UCL Genetics Institute, 'The majority of African Americans have ancestry similar to the Yoruba people in West Africa, confirming that most African slaves came from this region. In areas of the Americas historically under Spanish rule, populations also have ancestry related to what is now Senegal and Gambia. Records show that around a third of the slaves sent to Spanish America in the 17th Century came from this region, and we can see the genetic evidence of this in modern Americans really clearly.'

These genetic findings also uncover previously unknown migration. ‘We found a clear genetic contribution from the Basques in modern-day Maya in Mexico’, said Professor Capelli. ‘This suggests that the Basque also took part in the colonisation of the Americas, coming over either with the Spanish conquistadores or in later waves of migration’.

'The differences in European ancestry between the Caribbean islands and mainland American population that we found were also previously unknown. It is likely that these differences reflect different patterns of migration between the Caribbean and mainland America.'

'These results show just how powerful a genetic approach can be when it comes to uncovering hidden patterns of ancestry. We hope to use the same approach to look at other populations with diverse genetic contributions, such as Brazilians,' said Professor Capelli.

Source: University of Oxford [March 24, 2015]

An international team of scientists led by the University of Leicester has discovered a new species of fossil in England -- and identified it as an ancient parasitic intruder.

The fossil species found in 425-million year old rocks in Herefordshire, in the Welsh borderland, is described as 'exceptionally well preserved.' The specimens range from about 1 to 4 millimeters long.

The fossil species -- a 'tongue worm', which has a worm-like body and a head and two pairs of limbs -- is actually a parasite whose representatives today live internally in the respiratory system of a host, which it enters when it is eaten.

The new fossil, which was originally entirely soft-bodied, is the first fossil tongue worm species to be found associated with its host, which in this case is a species of ostracod -- a group of micro-arthropods (crabs, spiders and insects are also arthropods) with two shells that are joined at a hinge.

Professor David Siveter, of the Department of Geology at the University of Leicester made the discovery working alongside researchers from the Universities of Oxford, Imperial College London and Yale, USA. Their research is published in the journal Current Biology and was supported by The Natural Environmental Research Council, together with the Leverhulme Trust, the John Fell Oxford University Press (OUP) Research Fund and Yale Peabody Museum of Natural History.

Professor Siveter said: "This discovery is important not only because examples of parasites are exceptionally rare in the fossil record, but also because the possible host of fossil tongue worms -- and the origin of the lifestyle of tongue worms -- has been the subject of much debate.

"This discovery affirms that tongue worms were 'external' parasites on marine invertebrate animals at least 425 million years ago; it also suggests that tongue worms likely found their way into land-based environments and associated hosts in parallel with the movement of vertebrates onto the land by some 125 million years later."

Professor Siveter said tongue worms -- technically termed pentastomids -- are in fact not worms at all; they are an unusual group of tiny and widespread parasitic arthropods. Their fossils are exceptionally rare and until now are known only from a handful of isolated juvenile specimens.

Today they are known from about 140 species, nearly all of which are parasitic on vertebrate animals, particularly reptiles and including humans. Some of the fossil tongue worm specimens occur inside the shell, near the eggs of the ostracod; others are attached to the external surface of its shell, a unique position for any fossil or living tongue worm.

Professor Siveter added: "The tongue worm and its host lived in a sea that 425 million years ago -- during the Silurian period of geological time -- covered much of southern Britain, which was positioned then in warm southerly subtropical latitudes. The animals died and were preserved when a volcanic ash rained down upon them. The new species has been named Invavita piratica, which means an 'ancient intruder' and 'piracy', referring to its parasitic lifestyle in the sea."

The fossils have been reconstructed as virtual fossils by 3D computer modelling.

Source: University of Leicester [May 21, 2015]

The world's largest canyon may lie under the Antarctic ice sheet, according to analysis of satellite data by a team of scientists, led by Durham University.

Although the discovery needs to be confirmed by direct measurements, the previously unknown canyon system is thought to be over 1,000km long and in places as much as 1km deep, comparable in depth to the Grand Canyon in USA, but many times longer.

The canyon system is made up of a chain of winding and linear features buried under several kilometres of ice in one of the last unexplored regions of the Earth's land surface: Princess Elizabeth Land (PEL) in East Antarctica. Very few measurements of the ice thickness have been carried out in this particular area of the Antarctic, which has led to scientists dubbing it one of Antarctica's two 'Poles of Ignorance'.

The researchers believe that the landscape beneath the ice sheet has probably been carved out by water and is either so ancient that it was there before the ice sheet grew or it was created by water flowing and eroding beneath the ice.

Although not visible to the naked eye, the subglacial landscape can be identified in the surface of the ice sheet.

Faint traces of the canyons were observed using satellite imagery and small sections of the canyons were then found using radio-echo sounding data, whereby radio waves are sent through the ice to map the shape of the rock beneath it. These are very large features which appear to reach from the interior of Princess Elizabeth Land to the coast around the Vestfold Hills and the West Ice Shelf.

The canyons may be connected to a previously undiscovered subglacial lake as the ice surface above the lake shares characteristics with those of large subglacial lakes previously identified. The data suggests the area of the lake could cover up to 1250km², more than 80 times as big as Lake Windermere in the English Lake District.

An airborne survey taking targeted radio-echo sounding measurements over the whole buried landscape is now underway with the aim of unambiguously confirming the existence and size of the canyon and lake system, with results due later in 2016.

Lead researcher, Dr Stewart Jamieson, from the Department of Geography at Durham University in the UK, said: "Our analysis provides the first evidence that a huge canyon and a possible lake are present beneath the ice in Princess Elizabeth Land. It's astonishing to think that such large features could have avoided detection for so long.

"This is a region of the Earth that is bigger than the UK and yet we still know little about what lies beneath the ice. In fact, the bed of Antarctica is less well known than the surface of Mars. If we can gain better knowledge of the buried landscape we will be better equipped to understand how the ice sheet responds to changes in climate."

Co-Author Dr Neil Ross from Newcastle University in the UK, said: "Antarctic scientists have long recognised that because the way ice flows, the landscape beneath the ice sheet was subtly reflected in the topography of the ice sheet surface. Despite this, these vast deep canyons and potential large lake had been overlooked entirely.

"Our identification of this landscape has only been possible through the recent acquisition, compilation and open availability of satellite data by many different organisations (e.g. NASA, ESA and the US National Snow and Ice Data Center), to whom we are very grateful, and because of some serendipitous reconnaissance radio-echo sounding data acquired over the canyons by the ICECAP project during past Antarctic field seasons."

Co-Author Professor Martin Siegert, from the Grantham Institute at Imperial College London, UK, said: "Discovering a gigantic new chasm that dwarfs the Grand Canyon is a tantalising prospect. Geoscientists on Antarctica are carrying out experiments to confirm what we think we are seeing from the initial data, and we hope to announce our findings at a meeting of the ICECAP2 collaboration, at Imperial, later in 2016.

"Our international collaboration of US, UK, Indian, Australian and Chinese scientists are pushing back the frontiers of discovery on Antarctica like nowhere else on earth. But the stability of this understudied continent is threatened by global warming, so all the countries of the world now must rapidly reduce their greenhouse gas emissions and limit the damaging effects of climate change."

>The research is >published in >Geology>.

Source: Durham University [January 13, 2016]

Scientists from the Department of Earth Sciences at Royal Holloway, University of London together with colleagues from the USA, Russia and China, have discovered that forest fires across the globe were more common between 300 and 250 million years ago than they are today. This is thought to be due to higher level of oxygen in the atmosphere at that time.

The study which was published in the journal Frontiers in Plant Science, found that peats that were to become coal contained high levels of charcoal that could only be explained by the high levels of fire activity.

The team used the data from charcoal in coal to propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2)) that mass balance models predict prevailed. At higher levels of p(O2), increased fire activity would have rendered vegetation with high moisture contents more susceptible to ignition and would have facilitated continued combustion.

In the study they examine the environmental and ecological factors that would have impacted fire activity and conclude that of these factors p(O2) played the largest role in promoting fires in Late Paleozoic peat-forming environments and, by inference, ecosystems generally, when compared with their prevalence in the modern world.

Professor Andrew Scott, one of the lead authors, said: "High oxygen levels in the atmosphere at this time has been proposed for some time and may be why there were giant insects and arthropods at this time but our research indicates that there was a significant impact on the prevalence and scale of wildfires across the globe and this would have affected not only the ecology of the plants and animals but also their evolution."

Professor Scott and his colleagues and students at Royal Holloway have pioneered the study of fire in Earth's deep past. Professor Scott, added: "We have been able to show that wildfire was an important element in Earth System many hundreds of millions of years before the arrival of humans."

Source: University of Royal Holloway London [October 27, 2015]

Placental mammals consist of three main groups that diverged rapidly, evolving in wildly different directions: Afrotheria (for example, elephants and tenrecs), Xenarthra (such as armadillos and sloths) and Boreoeutheria (all other placental mammals). The relationships between them have been a subject of fierce controversy with multiple studies coming to incompatible conclusions over the last decade leading some researchers to suggest that these relationships might be impossible to resolve.

There are thus many outstanding questions such as which is the oldest sibling of the three? Did the mammals go their separate ways due to South America and Africa breaking apart? And if not, when did placentals split up?

"This has been one of the areas of greatest debate in evolutionary biology, with many researchers considering it impossible to resolve," said lead author Dr Tarver of Bristol's School of Earth Sciences. "Now we've proven these problems can be solved -- you just need to analyse genome-scale datasets using models that accurately reflect genomic evolution."

The researchers assembled the largest mammalian phylogenomic dataset ever collected before testing it with a variety of models of molecular evolution, choosing the most robust model and then analysing the data using several supercomputer clusters at the University of Bristol and the University of Texas Advanced Computing Centre. "We tested it to destruction," said Dr Tarver. "We threw the kitchen sink at it."

"A complication in reconstructing evolutionary histories from genomic data is that different parts of genomes can and often do give conflicting accounts of the history," said Dr Siavash Mirarab at the University of California San Diego, USA. "Individual genes within the same species can have different histories. This is one reason why the controversy has stood so long -- many thought the relationships couldn't be resolved."

To address the complexities of analysing large numbers of genes shared among many species, the researchers paired two fundamentally different approaches -- concatenated and coalescent-based analyses -- to confirm the findings. When the dust settled, the team had a specific family tree showing that Atlantogenata (containing the sibling groups of African Afrotheria and the South American Xenarthra) is the sister group to all other placentals.

Because many conflicting family trees have already been published, the team then gathered three of the most influential rivals and tested them against each other with the same model. All of the previous studies suddenly fell into line, their data agreeing with Tarver and colleagues.

With the origins of the family tree resolved, what does this mean for placental mammals? The researchers folded in another layer -- a molecular clock analysis. "The molecular clock analysis uses a combination of fossils and genomic data to estimate when these lineages diverged from each other," said author Dr Mario Dos-Reis of Queen Mary London, UK. "The results show that the afrotherians and xenarthrens diverged from one another around 90 million years ago."

Previously, scientists thought that when Africa and South America separated from each other over 100 million years ago, they broke up the family of placental mammals, who went their separate evolutionary ways divided by geography. But the researchers found that placental mammals didn't split up until after Africa and South America had already separated.

"We propose that South America's living endemic Xenarthra (for exmaple, sloths, anteaters, and armadillos) colonized the island-continent via overwater dispersal," said study author Dr Rob Asher of the University of Cambridge, UK.

Dr Asher suggests that this isn't as difficult as you might think. Mammals are among the great adventurers of the animal kingdom, and at the time the proto-Atlantic was only a few hundred miles wide. We already know that New World monkeys crossed the Atlantic later, when it was much bigger, probably on rafts formed from storm debris. And, of course, mammals repeatedly colonised remote islands like Madagascar.

"You don't always need to overturn the status quo to make a big impact," said Dr Tarver. "All of the competing hypotheses had some evidence to support them -- that's precisely why it was the source of such controversy. Proving the roots of the placental family tree with hard empirical evidence is a massive accomplishment."

The findings are published in Genome Biology and Evolution journal.

Source: University of Bristol [February 15, 2016]

Scientists from the Universities of Bristol and Málaga have proposed that the long extinct marsupial lion hunted in a very unique way -- by using its teeth to hold prey before dispatching them with its huge claws.

The marsupial lion, or Thylacoleo carnifex, was a predator in the Pleistocene era of Australia and was about the same size as a large jaguar.

It was known to have existed from around two-and-a-half-million years ago until as recently as a few tens of thousands of years ago.

The animal is depicted on native Australian cave art and some speculate it still survives as the "Queensland Tiger."

As its name suggests, the marsupial lion has long been presumed to be a cat-like predator, despite lacking large canine teeth -- instead it had large, protruding incisors that have been suggested to be canine substitutes.

Thylacoleo was a powerful beast but, as other researchers have noted, it had limbs of different proportions to a lion, suggesting it was not a fast.

It also sported a very large claw on its hand, similar to the dew claw of cats but of a much bigger size, with a bony sheath foisted on a mobile first digit (thumb).

The new study, >published in Paleobiology by Christine Janis, a Marie Curie Research Fellow at the University of Bristol (currently on a leave of absence from a professorship at Brown University, USA) with colleagues Borja Figueirido and Alberto Martín-Serra from the University of Málaga, Spain looked at the elbow joints of a large number of living mammals.

This showed a strong association between the anatomy of the humerus (upper arm bone) where it articulates with the forelimb and the locomotor behaviour of mammals.

Animals more specialized for running (like a dog) have a joint indicating movement limited for back and forwards, stabilising their bodies on the ground, while animals more specialised for climbing (like a monkey) have a joint that allows for rotation of the hand around the elbow. Modern cats, which (unlike dogs) use their forelimbs to grapple with their prey, have an elbow joint of intermediate shape.

Christine Janis said: "If Thylacoleo had hunted like a lion using its forelimbs to manipulate its prey, then its elbow joint should have been lion-like."

"But, surprisingly, it a unique elbow-joint among living predatory mammals -- one that suggested a great deal of rotational capacity of the hand, like an arboreal mammal, but also features not seen in living climbers, that would have stabilized the limb on the ground (suggesting that it was not simply a climber)."

Christine Janis and colleagues proposed that this unique elbow joint, in combination with the huge "dew claw" on a mobile thumb, would have allowed the marsupial lion to use that claw to kill its prey.

In contrast the large incisors were blunt. While Thylacoleo had massive shearing teeth in the back of its jaw, the incisors appear to have functioned better for gripping than for piercing flesh in a killing bite.

They concluded that, unlike a real lion, which holds its prey with its claws, and kills it with its teeth, the marsupial lion -- unlike any living predator -- used its teeth to hold its prey, while it despatched it with its huge claws.

Source: University of Bristol [August 16, 2016]