Why expressive brows might have mattered in human evolution

Eyebrows on fleek: Model of a modern human skull next to Kabwe 1.

Highly mobile eyebrows that can be used to express a wide range of subtle emotions may have played a crucial role in human survival, new research from the University of York suggests.

Like the antlers on a stag, a pronounced brow ridge was a permanent signal of dominance and aggression in our early ancestors, which modern humans traded in for a smooth forehead with more visible, hairy eyebrows capable of a greater range of movement.

Mobile eyebrows gave us the communication skills to establish large, social networks; in particular to express more nuanced emotions such as recognition and sympathy, allowing for greater understanding and cooperation between people.

The study contributes to a long-running academic debate about why other hominins, including our immediate ancestors, had gigantic brow ridges while anatomically modern humans evolved flatter foreheads.

Senior author of the paper, Paul O'Higgins, Professor of Anatomy at the University of York, said: "Looking at other animals can offer interesting clues as to what the function of a prominent brow ridge may have been. In mandrills, dominant males have brightly coloured swellings on either side of their muzzles to display their status. The growth of these lumps is triggered by hormonal factors and the bones underlying them are pitted with microscopic craters -- a feature that can also be seen in the brow bones of archaic hominins."

"Sexually dimorphic display and social signalling is a convincing explanation for the jutting brows of our ancestors. Their conversion to a more vertical brow in modern humans allowed for the display of friendlier emotions which helped form social bonds between individuals."

Using 3D engineering software, the researchers looked at the iconic brow ridge of a fossilised skull, known as Kabwe 1, held in the collections of the National History Museum.

It belonged to a species of archaic hominin -- Homo heidelbergensis, who lived between 600,000 and 200,000 years ago.

The researchers discounted two theories commonly put forward to explain protruding brow ridges: that they were needed to fill the space where the flat brain cases and eye sockets of archaic hominins met, and that the ridge acted to stabilise their skulls from the force of chewing.

Professor O'Higgins said: "We used modelling software to shave back Kabwe's huge brow ridge and found that the heavy brow offered no spatial advantage as it could be greatly reduced without causing a problem. Then we simulated the forces of biting on different teeth and found that very little strain was placed on the brow ridge. When we took the ridge away there was no effect on the rest of the face when biting.

"Since the shape of the brow ridge is not driven by spatial and mechanical requirements alone, and other explanations for brow ridges such as keeping sweat or hair out of eyes have already been discounted, we suggest a plausible contributing explanation can be found in social communication."

According to the researchers, our communicative foreheads started off as a side-effect of our faces getting gradually smaller over the past 100,000 years. This process has become particularly rapid in last 20,000 years and more recently, as we switched from being hunter gatherers to agriculturalists -- a lifestyle that meant less variety in both diet and physical effort.

Co-author of the paper, Dr Penny Spikins from the Department of Archaeology at the University of York, said: "Modern humans are the last surviving hominin. While our sister species the Neanderthals were dying out, we were rapidly colonising the globe and surviving in extreme environments. This had a lot to do with our ability to create large social networks -- we know, for example, that prehistoric modern humans avoided inbreeding and went to stay with friends in distant locations during hard times.

"Eyebrow movements allow us to express complex emotions as well as perceive the emotions of others. A rapid "eyebrow flash" is a cross-cultural sign of recognition and openness to social interaction and pulling our eyebrows up at the middle is an expression of sympathy. Tiny movements of the eyebrows are also a key component to identifying trustworthiness and deception. On the flip side it has been shown that people who have had botox which limits eyebrow movement are less able to empathise and identify with the emotions of others.

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First human migration out of Africa more geographically widespread than previously thought

Fossil finger bone of Homo sapiens from the Al Wusta site, Saudi Arabia.

A project led by the Max Planck Institute for the Science of Human History has discovered a fossilized finger bone of an early modern human in the Nefud Desert of Saudi Arabia, dating to approximately 90,000 years ago. The discovery, described in Nature Ecology and Evolution, is the oldest directly dated Homo sapiens fossil outside of Africa and the Levant and indicates that early dispersals into Eurasia were more expansive than previously thought.

Researchers conducting archaeological fieldwork in the Nefud Desert of Saudi Arabia have discovered a fossilized finger bone of an early member of our species, Homo sapiens. The discovery is the oldest directly dated Homo sapiens fossil outside of Africa and the immediately adjacent Levant, and indicates that early dispersals into Eurasia were more expansive than previously thought. Prior to this discovery, it was thought that early dispersals into Eurasia were unsuccessful and remained restricted to the Mediterranean forests of the Levant, on the doorstep of Africa. The finding from the Al Wusta site shows that there were both multiple dispersals out of Africa, and these spread further than previously known.

Oldest directly dated Homo sapiens fossil outside of Africa and the Levant

The results, published in Nature Ecology and Evolution, detail the discovery made at the site of Al Wusta, an ancient fresh-water lake located in what is now the hyper-arid Nefud Desert. Numerous animal fossils, including those of hippopotamus and tiny fresh water snails were found at Al Wusta, as well as abundant stone tools made by humans. Among these finds was a well preserved and small fossil, just 3.2 cm long, which was immediately recognized as a human finger bone. The bone was scanned in three dimensions and its shape compared to various other finger bones, both of recent Homo sapiens individuals and bones from other species of primates and other forms of early humans, such as Neanderthals. The results conclusively showed that the finger bone, the first ancient human fossil found in Arabia, belonged to our own species. Using a technique called uranium series dating, a laser was used to make microscopic holes in the fossil and measure the ratio between tiny traces of radioactive elements. These ratios revealed that the fossil was 88,000 years old. Other dates obtained from associated animals fossils and sediments converged to a date of approximately 90,000 years ago. Further environmental analyses also revealed the site to have been a freshwater lake in an ancient grassland environment far removed from today's deserts.

Lead author Dr. Huw Groucutt, of the University of Oxford and the Max Planck Institute for the Science of Human History, states, "This discovery for the first time conclusively shows that early members of our species colonized an expansive region of southwest Asia and were not just restricted to the Levant. The ability of these early people to widely colonize this region casts doubt on long held views that early dispersals out of Africa were localized and unsuccessful."

Modern deserts of the Arabian Peninsula were once lush grasslands that humans were able to colonize

Project Lead, Professor Michael Petraglia of the Max Planck Institute for the Science of Human History adds, "The Arabian Peninsula has long been considered to be far from the main stage of human evolution. This discovery firmly puts Arabia on the map as a key region for understanding our origins and expansion to the rest of the world. As fieldwork carries on, we continue to make remarkable discoveries in Saudi Arabia."

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Brewing up Earth's earliest life

White Island, New Zealand. Researchers have found that a class of molecules called sulfidic anions may have been abundant in Earth’s lakes and rivers.

Around 4 billion years ago, Earth was an inhospitable place, devoid of oxygen, bursting with volcanic eruptions, and bombarded by asteroids, with no signs of life in even the simplest forms. But somewhere amid this chaotic period, the chemistry of the Earth turned in life's favor, giving rise, however improbably, to the planet's very first organisms.

What prompted this critical turning point? How did living organisms rally in such a volatile world? And what were the chemical reactions that brewed up the first amino acids, proteins, and other building blocks of life? These are some of the questions researchers have puzzled over for decades in trying to piece together the origins of life on Earth.

Now planetary scientists from MIT and the Harvard-Smithsonian Center for Astrophysics have identified key ingredients that were present in large concentrations right around the time when the first organisms appeared on Earth.

The researchers found that a class of molecules called sulfidic anions may have been abundant in Earth's lakes and rivers. They calculate that, around 3.9 billion years ago, erupting volcanoes emitted huge quantities of sulfur dioxide into the atmosphere, which eventually settled and dissolved in water as sulfidic anions -- specifically, sulfites and bisulfites. These molecules likely had a chance to accumulate in shallow waters such as lakes and rivers.

"In shallow lakes, we found these molecules would have been an inevitable part of the environment," says Sukrit Ranjan, a postdoc in MIT's Department of Earth, Atmospheric and Planetary Sciences. "Whether they were integral to the origin of life is something we're trying to work out."

Preliminary work by Ranjan and his collaborators suggest that sulfidic anions would have sped up the chemical reactions required to convert very simple prebiotic molecules into RNA, a genetic building block of life.

"Prior to this work, people had no idea what levels of sulfidic anions were present in natural waters on early Earth; now we know what they were," Ranjan says. "This fundamentally changes our knowledge of early Earth and has had direct impact on laboratory studies of the origin of life."

Ranjan and his colleagues published their results today in the journal Astrobiology.

Setting early Earth's stage

In 2015, chemists from Cambridge University, led by John Sutherland, who is a co-author on the current study, discovered a way to synthesize the precursors to RNA using just hydrogen cyanide, hydrogen sulfide, and ultraviolet light -- all ingredients that are thought to have been available on early Earth, before the appearance of the first life forms.

From a chemistry point of view, the researchers' case was convincing: The chemical reactions they carried out in the laboratory overcame longstanding chemical challenges, to successfully yield the genetic building blocks to life. But from a planetary science standpoint, it was unclear whether such ingredients would have been sufficiently abundant to jumpstart the first living organisms.

For instance, comets may have had to rain down continuously to bring enough hydrogen cyanide to Earth's surface. Meanwhile, hydrogen sulfide, which would have been released in huge amounts by volcanic eruptions, would have mostly stayed in the atmosphere, as the molecule is relatively insoluble in water, and therefore would not have had regular opportunities to interact with hydrogen cyanide.

Instead of approaching the origins-of-life puzzle from a chemistry perspective, Ranjan looked at it from a planetary perspective, attempting to identify the actual conditions that might have existed on early Earth, around the time the first organisms appeared.

"The origins-of-life field has traditionally been led by chemists, who try to figure out chemical pathways and see how nature might have operated to give us the origins of life," Ranjan says. "They do a really great job of that. What they don't do in as much detail is, they don't ask what were conditions on early Earth like before life? Could the scenarios they invoke have actually happened? They don't know as much what the stage setting was."

Cranking up the ingredients for life

In August 2016, Ranjan gave a talk at Cambridge University about volcanism on Mars and the types of gases that would have been emitted by such eruptions in the red planet's oxygenless atmosphere. Chemists at the talk realized that the same general conditions would have occurred on Earth prior to the start of life.

"They took away from that [talk] that, on early Earth, you don't have much oxygen, but you do have sulfur dioxide from volcanism," Ranjan recalls. "As a consequence, you should have sulfites. And they said, 'Can you tell us how much of this molecule there would have been?' And that's what we set out to constrain."

To do so, he started with a volcanism model developed previously by Sara Seager, MIT's Class of 1941 Professor of Planetary Sciences, and her former graduate student Renyu Hu.

"They did a study where they asked, 'Suppose you take the Earth and just crank up the amount of volcanism on it. What concentrations of gases do you get in the atmosphere?'" Ranjan says.

He consulted the geological record to determine the amount of volcanism that likely took place around 3.9 billion years ago, around the time the first life forms are thought to have appeared, then looked up the types and concentrations of gases that this amount of volcanism would have produced according to Seager and Hu's calculations.

Next, he wrote a simple aqueous geochemistry model to calculate how much of these gases would have been dissolved in shallow lakes and reservoirs -- environments that would have been more conducive to concentrating life-forming reactions, versus vast oceans, where molecules could easily dissipate.

Interestingly, he consulted the literature in a rather unexpected subject while conducting these calculations: winemaking -- a science that involves, in part, dissolving sulfur dioxide in water to produce sulfites and bisulfites under oxygenless conditions similar to those on early Earth.

"When we were working on this paper, a lot of the constants and data we pulled out were from the wine chemistry journals, because it's where we have anoxic environments here on modern Earth," Ranjan says. "So we took aspects of wine chemistry and asked: 'Suppose we have x amount of sulfur dioxide. How much of that dissolves in water, and then what does it become?'"

Community cross-talk

Ultimately, he found that, while volcanic eruptions would have spewed huge quantities of both sulfur dioxide and hydrogen sulfide into the atmosphere, it was the former that dissolved more easily in shallow waters, producing large concentrations of sulfidic anions, in the form of sulfites and bisulfites.

"During major volcanic eruptions, you might have had up to millimolar levels of these compounds, which is about laboratory-level concentrations of these molecules, in the lakes," Ranjan says. "That is a titanic amount."

The new results point to sulfites and bisulfites as a new class of molecules -- ones that were actually available on early Earth -- that chemists can now test in the lab, to see whether they can synthesize from these molecules the precursors for life.

Early experiments led by Ranjan's colleagues suggest that sulfites and bisulfites may have indeed encouraged biomolecules to form. The team carried out chemical reactions to synthesize ribonucleotides with sulfites and bisulfites, versus with hydrosulfide, and found the former were able to produce ribonucleotides and related molecules 10 times faster than the latter, and at higher yields. More work is needed to confirm whether sulfidic anions were indeed early ingredients in brewing up the first life forms, but there is now little doubt that these molecules were part of the prebiotic milieu.

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Dead star circled by light

This new picture created from images from telescopes on the ground and in space tells the story of the hunt for an elusive missing object hidden amid a complex tangle of gaseous filaments in one of our nearest neighboring galaxies, the Small Magellanic Cloud. The reddish background image comes from the NASA/ESA Hubble Space Telescope and reveals the wisps of gas forming the supernova remnant 1E 0102.2-7219 in green. The red ring with a dark center is from the MUSE instrument on ESO's Very Large Telescope and the blue and purple images are from the NASA Chandra X-Ray Observatory. The blue spot at the center of the red ring is an isolated neutron star with a weak magnetic field, the first identified outside the Milky Way.

Spectacular new pictures, created from images from both ground- and space-based telescopes, tell the story of the hunt for an elusive missing object hidden amid a complex tangle of gaseous filaments in the Small Magellanic Cloud, about 200,000 light-years from Earth.

New data from the MUSE instrument on ESO's Very Large Telescope in Chile has revealed a remarkable ring of gas in a system called 1E 0102.2-7219, expanding slowly within the depths of numerous other fast-moving filaments of gas and dust left behind after a supernova. This discovery allowed a team led by Frédéric Vogt, an ESO Fellow in Chile, to track down the first ever isolated neutron star with low magnetic field located beyond our own Milky Way galaxy.

The team noticed that the ring was centred on an X-ray source that had been noted years before and designated p1. The nature of this source had remained a mystery. In particular, it was not clear whether p1 actually lies inside the remnant or behind it. It was only when the ring of gas -- which includes both neon and oxygen -- was observed with MUSE that the science team noticed it perfectly circled p1. The coincidence was too great, and they realised that p1 must lie within the supernova remnant itself. Once p1's location was known, the team used existing X-ray observations of this target from the [Chandra X-ray Observatory]  to determine that it must be an isolated neutron star, with a low magnetic field.

In the words of Frédéric Vogt: "If you look for a point source, it doesn't get much better than when the Universe quite literally draws a circle around it to show you where to look."

When massive stars explode as supernovae, they leave behind a curdled web of hot gas and dust, known as a supernova remnant. These turbulent structures are key to the redistribution of the heavier elements -- which are cooked up by massive stars as they live and die -- into the interstellar medium, where they eventually form new stars and planets.

Typically barely ten kilometres across, yet weighing more than our Sun, isolated neutron stars with low magnetic fields are thought to be abundant across the Universe, but they are very hard to find because they only shine at X-ray wavelengths. The fact that the confirmation of p1 as an isolated neutron star was enabled by optical observations is thus particularly exciting.

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Giant solar tornadoes put researchers in a spin

Composite image of an erupting solar prominence observed by SDO on Aug. 31, 2012.

Despite their appearance solar tornadoes are not rotating after all, according to a European team of scientists. A new analysis of these gigantic structures, each one several times the size of the Earth, indicates that they may have been misnamed because scientists have so far only been able to observe them using 2-dimensional images. Dr Nicolas Labrosse will present the work, carried out by researchers at the University of Glasgow, Paris Observatory, University of Toulouse, and Czech Academy of Sciences, at the European Week of Astronomy and Space Science (EWASS) in Liverpool on Friday 6 April.

Solar tornadoes were first observed in the early 20th century, and the term was re-popularised a few years ago when scientists looked at movies obtained by the AIA instrument on the NASA Solar Dynamics Observatory (SDO). These show hot plasma in extreme ultraviolet light apparently rotating to form a giant structure taking the shape of a tornado (as we know them on Earth).

Now, using the Doppler effect to add a third dimension to their data, the scientists have been able to measure the speed of the moving plasma, as well as its direction, temperature and density. Using several years' worth of observations, they were able to build up a more complete picture of the magnetic field structure that supports the plasma, in structures known as prominences.

Dr Nicolas Labrosse, lead scientist in the study, explains: "We found that despite how prominences and tornadoes appear in images, the magnetic field is not vertical, and the plasma mostly moves horizontally along magnetic field lines. However we see tornado-like shapes in the images because of projection effects, where the line of sight information is compressed onto the plane of the sky."

Dr Arturo López Ariste, another member of the team, adds: "The overall effect is similar to the trail of an aeroplane in our skies: the aeroplane travels horizontally at a fixed height, but we see that the trail starts above our heads and ends up on the horizon. This doesn't mean that it has crashed!"

Giant solar tornadoes -- formally called tornado prominences -- have been observed on the Sun for around a hundred years. They are so called because of their striking shape and apparent resemblance to tornadoes on Earth, but that is where the comparison ends.

Whereas terrestrial tornadoes are formed from intense winds and are very mobile, solar tornadoes are instead magnetized gas. They seem to be rooted somewhere further down the solar surface, and so stay fixed in place.

"They are associated with the legs of solar prominences -- these are beautiful concentrations of cool plasma in the very hot solar corona that can easily be seen as pink structures during total solar eclipses," adds Labrosse.

"Perhaps for once the reality is less complicated than what we see!" comments Dr Brigitte Schmieder, another scientist involved in the work.

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Hunting for dark matter in the smallest galaxies in the Universe

Dark matter makes up most of the mass of the Universe, yet it remains elusive.

Astrophysicists from the University of Surrey and the University of Edinburgh have created a new method to measure the amount of dark matter at the centre of tiny "dwarf" galaxies.

Dark matter makes up most of the mass of the Universe, yet it remains elusive. Depending on its properties, it can be densely concentrated at the centres of galaxies, or more smoothly distributed over larger scales. By comparing the distribution of dark matter in galaxies with detailed models, researchers can test or rule out different dark matter candidates.

The tightest constraints on dark matter come from the very smallest galaxies in the Universe, "dwarf galaxies." The smallest of these contain just a few thousand or tens of thousands of stars -- so-called "ultra-faint" dwarfs. Such tiny galaxies, found orbiting close to the Milky Way, are made up almost entirely of dark matter. If the distribution of dark matter in these tiny galaxies could be mapped out it could provide new and exciting information about its nature. However, being entirely devoid of gas and containing very few stars, until recently there was no viable method for making this measurement.

In a study published by the Monthly Notices of the Royal Astronomical Society (MNRAS), a team of scientists from the University of Surrey have developed a new method to calculate the inner dark matter density of dwarf galaxies, even if they have no gas and very few stars. The key to the method is to make use of one or more dense star clusters orbiting close to the centre of the dwarf.

Star clusters are gravitationally bound collections of stars that orbit inside galaxies. Unlike galaxies, star clusters are so dense that their stars gravitationally scatter from one another causing them to slowly expand. The research team made the key new insight when they realised that the rate of this expansion depends on the gravitational field that the star cluster orbits in and, therefore, on the distribution of dark matter in the host galaxy. The team used a large suite of computer simulations to show how the structure of star clusters is sensitive to whether dark matter is densely packed at the centre of galaxies, or more smoothly distributed. The team then applied their method to the recently discovered "ultra-faint" dwarf galaxy, Eridanus II, finding much less dark matter in its centre than many models would have predicted.

Dr Filippo Contenta from the University of Surrey and lead author of the study said: "We have developed a new tool to uncover the nature of dark matter and already the results are exciting. Eridanus II, one of the smallest galaxies known, has less dark matter in its centre than expected. If similar results are found for a larger sample of galaxies, this could have wide-ranging implications for the nature of dark matter."

Professor Mark Gieles, Professor of Astrophysics at the University of Surrey and Principal Investigator of the European Research Council (ERC) project that funded the project, added: "We started this ERC project with the hope that we could use star clusters to learn about dark matter so it is very exciting that it worked."

Professor Justin Read, a co-author on the study from the University of Surrey, added: "It is challenging to understand our results for Eridanus II if dark matter comprises a weakly interacting 'cold' particle -- the currently-favoured model for dark matter. One possibility is that the dark matter at the very centre of Eridanus II was "heated up" by violent star formation, as suggested by some recent numerical models. More tantalising, however, is the possibility is that dark matter is more complex than we have assumed to date."

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Paucity of phosphorus hints at precarious path for extraterrestrial life

This is a composite of infrared (shown as red), visible (green) and ultraviolet (violet) images of the Crab Nebula, with IR enhanced and visible/UV balanced to yield neutral star colors.

Work by Cardiff University astronomers suggests there may be a cosmic lack of a chemical element essential to life. Dr Jane Greaves and Dr Phil Cigan will present their results at the European Week of Astronomy and Space Science in Liverpool.

Greaves has been searching for phosphorus in the universe, because of its link to life on Earth. If this element -- with the chemical code P -- is lacking in other parts of the cosmos, then it could be difficult for extra-terrestrial life to exist.

She explains: "Phosphorus is one of just six chemical elements on which Earth organisms depend, and it is crucial to the compound adenosine triphosphate (ATP), which cells use to store and transfer energy. Astronomers have just started to pay attention to the cosmic origins of phosphorus and found quite a few surprises. In particular, P is created in supernovae -- the explosions of massive stars -- but the amounts seen so far don't match our computer models. I wondered what the implications were for life on other planets if unpredictable amounts of P are spat out into space and later used in the construction of new planets."

The team used the UK's William Herschel Telescope, sited on La Palma in the Canary islands, to observe infrared light from phosphorus and iron in the Crab Nebula, a supernova remnant around 6500 light years away in the direction of the constellation of Taurus.

Cigan, an expert on these stellar remnants, says: "This is only the second such study of phosphorus that has been made. The first looked at the Cassiopeia A (Cas A) supernova remnant, and so we are able to compare two different stellar explosions and see if they ejected different proportions of phosphorus and iron. The first element supports life, while the second is a major part of our planet's core."

The astronomers struggled with foggy nights at the telescope, back in November 2017, and are only just starting to get scientific results from a few hours of data.

Cigan cautions "These are our preliminary results, which we extracted only in the last couple of weeks! But at least for the parts of the Crab Nebula we were able to observe so far, there seems to be much less phosphorus than in Cas A. The two explosions seem to differ from each other, perhaps because Cas A results from the explosion of a rare super-massive star. We've just asked for more telescope time to go back and check, in case we've missed some phosphorus-rich regions in the Crab Nebula."

The preliminary results suggest that material blown out into space could vary dramatically in chemical composition. Greaves remarks: "The route to carrying phosphorus into new-born planets looks rather precarious. We already think that only a few phosphorus-bearing minerals that came to the Earth -- probably in meteorites -- were reactive enough to get involved in making proto-biomolecules.

'If phosphorus is sourced from supernovae, and then travels across space in meteoritic rocks, I'm wondering if a young planet could find itself lacking in reactive phosphorus because of where it was born? That is, it started off near the wrong kind of supernova? In that case, life might really struggle to get started out of phosphorus-poor chemistry, on another world otherwise similar to our own."

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Genetics of the modern heirs of the Inkas shed new lights about their origins and lineages

Iconic sacred citadelle of Machu Picchu, at the edge of the Andes and Amazon, symbol of the largest empire of the Pre Columbian Americas.

A multinational South American team from Peru, Brasil and Bolivia led by the Universidad de San Martin de Porres at Lima, Peru, published the first genetic study on the modern descendants of the imperial Inka lineages in the journal Molecular Genetics and Genomics. This work supported by funds from the Genographic Project (Geno 2.0), shows new insights about the Inkas origins and lineages.

The Inka people arrived to Cusco valley and in a few centuries they built the Tawantinsuyu, the largest empire in the Americas. The Tawantinsuyu was the cultural climax of 6,000 years of Central Andes civilizations overlapping modern countries of Peru, Bolivia, Ecuador, the South of Colombia and the North of Argentina and Chile. In contrast with the richness of archeological and cultural evidence, pre Columbian history vanishes in time as it intermingles with myths due to the lack of writing systems before the arrival of the European chroniclers. Very little is known about the Inka origins and some genetic information could help reconstruct part of their history. Unfortunately the mummies and bodily remains of the Inka emperors, worshiped as gods, were burnt and buried in unknown locations due to religious and political persecution by the Christian Conquistadors and Inquisitors, so no direct material remain to study their DNA. "Thus for now, only the genetic analysis of modern families of Inka descent could provide some clues about their ancestors" remarks geneticist Jose Sandoval, first author, working at Universidad de San Martin de Porres at Lima, Peru.

There were two foundational myths for the origin of the Inkas before they established in Cusco valley to build their capital city. One is that Manco Capac and Mama Ocllo, considered children of the Sun God and founder parents of the civilization, came from Lake Titicaca about 500 km southwards from the border of North Bolivia and South Peru, more or less the same region where Tiwanaku empire existed a few centuries before. The second myth narrates that four Ayar brothers, with divine powers, came out from the caves inside of a hill in the area of Paccarictambo, 50 km south of Cusco and only one of them, Manco, arrived to the Cusco valley. Concerning the succession of the rulers (between 12 to 14), most chroniclers mention only one patrilineal heritage, however other authors think that it was a complex selection of military and administrative skills not necessarily electing the son of a previous Inka. "A unique patrilineal cluster would be expected in the first case. In the second case, two or more patrilineal pattern will be evident" says geneticist Ricardo Fujita, senior author, also at Universidad de San Martin de Porres." The research team included historian Ronald Elward, who studied documentation of twelve Inka noble families and followed up from the conquista times to their contemporary descendants. "Most of them still living in the towns of San Sebastian and San Jeronimo, Cusco, Peru, at present, are probably the most homogeneous group of Inka lineage" says Elward.

Markers for Y chromosome and mtDNA were used for the genetic analysis of these families and compared with a database for 2400 native individuals from Peru, Bolivia, Ecuador and Brazil. "The results show distinctive patrilineal origins to two founder individuals who lived between 1000 to 1500 AD, a period between the decline of former Tiwanaku (south) and Wari (north) contemporary empires, and the rise of the Inca empire a few centuries later" says geneticist Fabricio Santos from the Universidad Federal de Minas Gerais at Belo Horizonte, Brazil. The first patrilineal haplotype named AWKI-1 (awki means crown prince in quechua language) is found in the putative families descending of 2 earlier Incas Yahuar Huacac and Viracocha. The same pattern of the Inca descendants was also found in individuals living south to Cusco, mainly in Aymaras of Peru and Bolivia. The second patrilineal haplotype named AWKI-2 was found in one descendant of a more recent Inca, Huayna Capac, father of the two brothers (Huascar and Atahualpa) who were fighting a fraternal war over the empire at the arrival of the Conquistadors. "AWKI-2 is also found in dozens of individuals from different locations in the Andes and occasionally in the Amazon, suggesting a populational expansion" says Dr. Santos.

"In addition to San Sebastian and San Jeronimo, most locations of AWKI-1, AWKI-2 were southwards to Cusco including the basin of lake Titicaca and neighboring Paccarictambo, in agreement with the two foundational myths of the Incas" says Ricardo Fujita, "probably two pictures at different times of the same journey with final destination Cusco" adds Fujita. "It is also remarkable that in these contemporary Inka noblility families there is a continuity since pre Columbian times" says Ronald Elward. The analysis of their mtDNA suggested a highly varied matrilineal marker whose counterparts are found all over the Andes reflecting a high genetic flow. "This probably reflects the political alliances by arranged marriages between Cusco nobility and daughters of lords of kingdoms and chiefdoms all over the empire" states Jose Sandoval.

This work is the continuation of several studies performed by the team to reconstruct South American history by Genetics and also funded by a previous grant of the Genographic Project (Geno 1.0) led in South America by Fabricio Santos. Two published works included the unique ancient roots of the Uros, people from the Floating Islands of the Lake Titicaca and the Quechwa-Lamistas in Peruvian Amazon. Modern Uros are Aymara speaking people that some have thought to be people from the Aymara ethnia who profited tourism by living on the floating islands. However the team showed that they were genetically isolated people who had lost their original Uro language, shifting to more the widely used Aymara language. On the other hand the Kechwa-Lamista are Amazonian people who speak the Andean Quechua language and they were presumed descendants of Andeans Chancas, former enemies of the Incas, and were chased by them towards the Amazon. DNA showed that they are actually descendants of linguistically different Amazonian people who were gathered by Catholic missions and were taught the Quechua language (learn by the missionaries at the Andes) for a better evangelization.

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Older adults grow just as many new brain cells as young people

Rendering of a brain.

Researchers show for the first time that healthy older men and women can generate just as many new brain cells as younger people.

There has been controversy over whether adult humans grow new neurons, and some research has previously suggested that the adult brain was hard-wired and that adults did not grow new neurons. This study, to appear in the journal Cell Stem Cell on April 5, counters that notion. Lead author Maura Boldrini, associate professor of neurobiology at Columbia University, says the findings may suggest that many senior citizens remain more cognitively and emotionally intact than commonly believed.

"We found that older people have similar ability to make thousands of hippocampal new neurons from progenitor cells as younger people do," Boldrini says. "We also found equivalent volumes of the hippocampus (a brain structure used for emotion and cognition) across ages. Nevertheless, older individuals had less vascularization and maybe less ability of new neurons to make connections."

The researchers autopsied hippocampi from 28 previously healthy individuals aged 14-79 who had died suddenly. This is the first time researchers looked at newly formed neurons and the state of blood vessels within the entire human hippocampus soon after death. (The researchers had determined that study subjects were not cognitively impaired and had not suffered from depression or taken antidepressants, which Boldrini and colleagues had previously found could impact the production of new brain cells.)

In rodents and primates, the ability to generate new hippocampal cells declines with age. Waning production of neurons and an overall shrinking of the dentate gyrus, part of the hippocampus thought to help form new episodic memories, was believed to occur in aging humans as well.

The researchers from Columbia University and New York State Psychiatric Institute found that even the oldest brains they studied produced new brain cells. "We found similar numbers of intermediate neural progenitors and thousands of immature neurons," they wrote. Nevertheless, older individuals form fewer new blood vessels within brain structures and possess a smaller pool of progenitor cells -- descendants of stem cells that are more constrained in their capacity to differentiate and self-renew.

Boldrini surmised that reduced cognitive-emotional resilience in old age may be caused by this smaller pool of neural stem cells, the decline in vascularization, and reduced cell-to-cell connectivity within the hippocampus. "It is possible that ongoing hippocampal neurogenesis sustains human-specific cognitive function throughout life and that declines may be linked to compromised cognitive-emotional resilience," she says.

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How birds can detect Earth’s magnetic field

Zebra finches.

Researchers at Lund University in Sweden have made a key discovery about the internal magnetic compass of birds. Biologists have identified a single protein without which birds probably would not be able to orient themselves using the Earth's magnetic field.

The receptors that sense the Earth's magnetic field are probably located in the birds' eyes. Now, researchers at Lund University have studied different proteins in the eyes of zebra finches and discovered that one of them differs from the others: only the Cry4 protein maintains a constant level throughout the day and in different lighting conditions.

Cry4 belongs to a group of proteins called cryptochromes. Normally they regulate the biological clock, but have also been considered significant for the magnetic sense. With this study, we now know which of the birds' cryptochromes do what.

"Cry4 is an ideal magnetoreceptor as the level of the protein in the eyes is constant. This is something we expect from a receptor that is used regardless of the time of day," explains Atticus Pinzón-Rodríguez, one of the researchers behind the study.

The conclusion is thus that this specific protein helps the magnetic sense to function, while other cryptochromes, whose levels in the body vary at different times of the day, take care of the biological clock instead.

Last year, Atticus Pinzón-Rodríguez and his colleagues noted that not only migratory birds navigate using a magnetic compass. Even resident birds that do not migrate in the spring and autumn have a magnetic sense and navigate using their internal magnetic compass. He now takes this one step further:

"This and last year's results indicate that other animals, perhaps all of them, have magnetic receptors and can pick up on magnetic fields."

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