Thursday, May 28, 2015

Out of Africa via Egypt

New research suggests that European and Asian (Eurasian) peoples originated when early Africans moved north - through the region that is now Egypt - to expand into the rest of the world. The findings, published in the American Journal of Human Genetics, answer a long-standing question as to whether early humans emerged from Africa by a route via Egypt, or via Ethiopia.

The extensive public catalogue of the genetic diversity in Ethiopian and Egyptian populations developed for the project also now provides a valuable, freely available, reference panel for future medical and anthropological studies in these areas.

Two geographically plausible routes have been proposed for humans to emerge from Africa: through the current Egypt and Sinai (Northern Route), or through Ethiopia, the Bab el Mandeb strait and the Arabian Peninsula (Southern Route). Some lines of evidence have previously favoured one, some the other.

"The most exciting consequence of our results is that we draw back the veil that has been hiding an episode in the history of all Eurasians, improving the understanding of billions of people of their evolutionary history," says Dr Luca Pagani, first author from the Wellcome Trust Sanger Institute and University of Cambridge. "It is exciting that, in our genomic era, the DNA of living people allows us to explore and understand events as ancient as 60,000 years ago."

The team produced whole-genome sequences from 225 people from modern Egypt and Ethiopia. In previous studies, they and others have shown that these modern populations have been subject to gene flow from West Asian populations, so they excluded the Eurasian contribution to the genomes of the modern African people.

The remaining masked genomic regions from Egyptian samples were more similar to non-African samples and present in higher frequencies outside Africa than the masked Ethiopian genomic regions, pointing to Egypt as the more likely gateway in the exodus to the rest of the world.

The team also used high-quality genomes to estimate the time that the populations split from one another: people outside Africa split from the Egyptian genomes more recently than from the Ethiopians (55,000 as opposed to 65, 000 years ago), supporting the idea that Egypt was last stop on the route out of Africa.

"While our results do not address controversies about the timing and possible complexities of the expansion out of Africa, they paint a clear picture in which the main migration out of Africa followed a Northern, rather than a Southern route," says Dr Toomas Kivisild, a senior author from the Department of Archaeology and Anthropology, University of Cambridge.

The Northern Route as the preferential direction taken out of Africa is in better agreement with the known genetic mixture of all non-Africans with Neanderthals, who were present in the Levant at the time, and with the recent discovery of early modern human fossils in Israel (close to the Northern Route) dating to around 55,000 years ago.

"This important study still leaves questions to answer," says Dr Chris Tyler-Smith, a senior author from the Wellcome Trust Sanger Institute. "For example, did other migrations also leave Africa around this time, but leave no trace in present-day genomes? To answer this, we need ancient genomes from populations along the possible routes. Similarly, by adding present-day genomes from Oceania, we can discover whether or not there was a separate, perhaps Southern, migration to these regions.

"Our approach shows how it is possible to use the latest genomic data and tools to answer these intriguing questions of our human origins and migrations."

Wednesday, May 27, 2015

A Section of Ancient Jerusalem’s Lower Aqueduct was Exposed in the Eastern Jerusalem

A section of Jerusalem’s Lower Aqueduct, which conveyed water to the city more than 2,000 years ago, was exposed in the Umm Tuba quarter (near Har Homa) during the construction of a sewer line in the neighborhood by the Gihon Company. This line is just part of an extensive project directed by Zohar Yinon, CEO of the Gihon Company Ltd, to install a modern sewer system for the benefit of the residents of Umm Tuba and Sur Bahar.

The Israel Antiquities Authority conducted an archaeological excavation there following the discovery of the aqueduct. According to Ya’akov Billig, the excavation director, “The Lower Aqueduct to Jerusalem, which the Hasmonean kings constructed more than two thousand years ago in order to provide water to Jerusalem, operated intermittently until about one hundred years ago. The aqueduct begins at the ‘En ‘Eitam spring, near Solomon’s Pools south of Bethlehem, and is approximately 21 kilometers long. Despite its length, it flows along a very gentle downward slope whereby the water level falls just one meter per kilometer of distance. At first, the water was conveyed inside an open channel and about 500 years ago, during the Ottoman period, a terra cotta pipe was installed inside the channel in order to better protect the water”.

The aqueduct’s route was built in open areas in the past, but with the expansion of Jerusalem in the modern era, it now runs through a number of neighborhoods: Umm Tuba, Sur Bahar, East Talpiot and Abu Tor. Since this is one of Jerusalem’s principal sources of water, the city’s rulers took care to preserve it for some two thousand years, until it was replaced about a century ago by a modern electrically operated system. Due to its historical and archaeological importance, the Israel Antiquities Authority is taking steps to prevent any damage to the aqueduct, and is working to expose sections of its remains, study them and make them accessible to the general public.

The Umm Tuba section of the aqueduct was documented, studied, and covered up again for the sake of future generations. Other sections of the long aqueduct have been conserved for the public in the Armon Ha-Natziv tunnels, on the Sherover promenade, around the Sultan's Pool and additional projects are planned whose themes include the Lower Aqueduct.

The Israel Antiquities Authority noted favorably the professional attitude and thorough efforts on the part of the Gihon Company regarding the excavation and discovery of antiquities.

Thursday, May 21, 2015

World's oldest stone tools challenge ideas about first toolmakers

Scientists working in the desert badlands of northwestern Kenya have found stone tools dating back 3.3 million years, long before the advent of modern humans, and by far the oldest such artifacts yet discovered. The tools, whose makers may or may not have been some sort of human ancestor, push the known date of such tools back by 700,000 years; they also may challenge the notion that our own most direct ancestors were the first to bang two rocks together to create a new technology.

The discovery is the first evidence that an even earlier group of proto-humans may have had the thinking abilities needed to figure out how to make sharp-edged tools. The stone tools mark "a new beginning to the known archaeological record," say the authors of a new paper about the discovery, published today in the leading scientific journal Nature.

"The whole site's surprising, it just rewrites the book on a lot of things that we thought were true," said geologist Chris Lepre of the Lamont-Doherty Earth Observatory and Rutgers University, a co-author of the paper who precisely dated the artifacts.

The tools "shed light on an unexpected and previously unknown period of hominin behavior and can tell us a lot about cognitive development in our ancestors that we can't understand from fossils alone," said lead author Sonia Harmand, of the Turkana Basin Institute at Stony Brook University and the Universite Paris Ouest Nanterre.

Hominins are a group of species that includes modern humans, Homo sapiens, and our closest evolutionary ancestors. Anthropologists long thought that our relatives in the genus Homo -- the line leading directly to Homo sapiens -- were the first to craft such stone tools. But researchers have been uncovering tantalizing clues that some other, earlier species of hominin, distant cousins, if you will, might have figured it out.

The researchers do not know who made these oldest of tools. But earlier finds suggest a possible answer: The skull of a 3.3-million-year-old hominin, Kenyanthropus platytops, was found in 1999 about a kilometer from the tool site. A K. platyops tooth and a bone from a skull were discovered a few hundred meters away, and an as-yet unidentified tooth has been found about 100 meters away.
The precise family tree of modern humans is contentious, and so far, no one knows exactly how K. platyops relates to other hominin species. Kenyanthropus predates the earliest known Homo species by a half a million years. This species could have made the tools; or, the toolmaker could have been some other species from the same era, such as Australopithecus afarensis, or an as-yet undiscovered early type of Homo.

Lepre said a layer of volcanic ash below the tool site set a "floor" on the site's age: It matched ash elsewhere that had been dated to about 3.3 million years ago, based on the ratio of argon isotopes in the material. To more sharply define the time period of the tools, Lepre and co-author and Lamont-Doherty colleague Dennis Kent examined magnetic minerals beneath, around and above the spots where the tools were found.

The Earth's magnetic field periodically reverses itself, and the chronology of those changes is well documented going back millions of years. "We essentially have a magnetic tape recorder that records the magnetic field ... the music of the outer core," Kent said. By tracing the variations in the polarity of the samples, they dated the site to 3.33 million to 3.11 million years.

Lepre's wife and another co-author, Rhoda Quinn of Rutgers, studied carbon isotopes in the soil, which along with animal fossils at the site allowed researchers to reconstruct the area's vegetation. This led to another surprise: The area was at that time a partially wooded, shrubby environment. Conventional thinking has been that sophisticated tool-making came in response to a change in climate that led to the spread of broad savannah grasslands, and the consequent evolution of large groups of animals that could serve as a source of food for human ancestors.

One line of thinking is that hominins started knapping -- banging one rock against another to make sharp-edged stones -- so they could cut meat off of animal carcasses, said paper co-author Jason Lewis of the Turkana Basin Institute and Rutgers. But the size and markings of the newly discovered tools "suggest they were doing something different as well, especially if they were in a more wooded environment with access to various plant resources," Lewis said. The researchers think the tools could have been used for breaking open nuts or tubers, bashing open dead logs to get at insects inside, or maybe something not yet thought of.

"The capabilities of our ancestors and the environmental forces leading to early stone technology are a great scientific mystery," said Richard Potts, director of the Human Origins Program at the Smithsonian's National Museum of Natural History, who was not involved in the research. The newly dated tools "begin to lift the veil on that mystery, at an earlier time than expected," he said.
Potts said he had examined the stone tools during a visit to Kenya in February.

"Researchers have thought there must be some way of flaking stone that preceded the simplest tools known until now," he said. "Harmand's team shows us just what this even simpler altering of rocks looked like before technology became a fundamental part of early human behavior."

Ancient stone artifacts from East Africa were first uncovered at Olduvai Gorge in Tanzania in the mid-20th century, and those tools were later associated with fossil discoveries in the 1960s of the early human ancestor Homo habilis. That species has been dated to 2.1 million to 1.5 million years ago.

Subsequent finds have pushed back the dates of humans' evolutionary ancestors, and of stone tools, raising questions about who first made that cognitive leap. The discovery of a partial lower jaw in the Afar region of Ethiopia, announced on March 4, pushes the fossil record for the genus Homo to 2.8 million years ago. Evidence from recent papers, the authors note, suggests that there is anatomical evidence that Homo had evolved into several distinct lines by 2 million years ago.

There is some evidence of more primitive tool use going back even before the new find. In 2009, researchers at Dikika, Ethiopia, dug up 3.39 million-year-old animal bones marked with slashes and other cut marks, evidence that someone used stones to trim flesh from bone and perhaps crush bones to get at the marrow inside. That is the earliest evidence of meat and marrow consumption by hominins. No tools were found at the site, so it's unclear whether the marks were made with crafted tools or simply sharp-edged stones. The only hominin fossil remains in the area dating to that time are from Australopithecus afarensis.

The new find came about almost by accident: Harmand and Lewis said that on the morning of July 9, 2011, they had wandered off on the wrong path, and climbed a hill to scout a fresh route back to their intended track. They wrote that they "could feel that something was special about this particular place." They fanned out and surveyed a nearby patch of craggy outcrops. "By teatime," they wrote, "local Turkana tribesman Sammy Lokorodi had helped [us] spot what [we] had come searching for."
By the end of the 2012 field season, excavations at the site, named Lomekwi 3, had uncovered 149 stone artifacts tied to tool-making, from stone cores and flakes to rocks used for hammering and others possibly used as anvils to strike on.

The researchers tried knapping stones themselves to better understand how the tools they found might have been made. They concluded that the techniques used "could represent a technological stage between a hypothetical pounding-oriented stone tool use by an earlier hominin and the flaking-oriented knapping behavior of [later] toolmakers." Chimpanzees and other primates are known to use a stone to hammer open nuts atop another stone. But using a stone for multiple purposes, and using one to crack apart another into a sharper tool, is more advanced behavior.

The find also has implications for understanding the evolution of the human brain. The toolmaking required a level of hand motor control that suggests that changes in the brain and spinal tract needed for such activity could have occurred before 3.3 million years ago, the authors said.

"This is a momentous and well-researched discovery," said paleoanthropologist Bernard Wood of George Washington University, who was not involved in the study. "I have seen some of these artifacts in the flesh, and I am convinced they were fashioned deliberately." Wood said he found it intriguing to see how different the tools are from so-called Oldowan stone tools, which up to now have been considered the oldest and most primitive.

Lepre, who has been conducting fieldwork in eastern Africa for about 15 years, said he arrived at the dig site about a week after the discovery. The site is several hours' drive on rough roads from the nearest town, located in a hot, dry landscape he said is reminiscent of Arizona and New Mexico. Lepre collected chunks of sediment from a series of depths and brought them back to Lamont-Doherty for analysis. He and Kent used a bandsaw to trim the samples into sugar cube-size blocks and inserted them into a magnetometer, which measured the polarity of tiny grains of the minerals hematite and magnetite contained in the sediment.

"The magnetics pretty much clinches that the age is something like 3.3 million years old," said Kent, who also is a professor at Rutgers.

Earlier dating work by Lepre and Kent helped lead to another landmark paper in 2011: a study that suggested Homo erectus, another precursor to modern humans, was using more advanced tool-making methods 1.8 million years ago, at least 300,000 years earlier than previously thought.
"I realized when you [figure out] these things, you don't solve anything, you just open up new questions," said Lepre. "I get excited, then realize there's a lot more work to do."

Tuesday, May 19, 2015

Most European men descend from a handful of Bronze Age forefathers

Geneticists from the University of Leicester have discovered that most European men descend from just a handful of Bronze Age forefathers, due to a 'population explosion' several thousand years ago.

The project, which was funded by the Wellcome Trust, was led by Professor Mark Jobling from the University of Leicester's Department of Genetics and the study is published in the prestigious journal Nature Communications.

The research team determined the DNA sequences of a large part of the Y chromosome, passed exclusively from fathers to sons, in 334 men from 17 European and Middle Eastern populations.

This research used new methods for analysing DNA variation that provides a less biased picture of diversity, and also a better estimate of the timing of population events.

This allowed the construction of a genealogical tree of European Y chromosomes that could be used to calculate the ages of branches. Three very young branches, whose shapes indicate recent expansions, account for the Y chromosomes of 64% of the men studied.

Professor Jobling said: "The population expansion falls within the Bronze Age, which involved changes in burial practices, the spread of horse-riding and developments in weaponry. Dominant males linked with these cultures could be responsible for the Y chromosome patterns we see today."

In addition, past population sizes were estimated, and showed that a continuous swathe of populations from the Balkans to the British Isles underwent an explosion in male population size between 2000 and 4000 years ago.

This contrasts with previous results for the Y chromosome, and also with the picture presented by maternally-inherited mitochondrial DNA, which suggests much more ancient population growth.

Previous research has focused on the proportion of modern Europeans descending from Paleolithic -- Old Stone Age -- hunter-gatherer populations or more recent Neolithic farmers, reflecting a transition that began about 10,000 years ago.

Chiara Batini from the University of Leicester's Department of Genetics, lead author of the study, added: "Given the cultural complexity of the Bronze Age, it's difficult to link a particular event to the population growth that we infer. But Y-chromosome DNA sequences from skeletal remains are becoming available, and this will help us to understand what happened, and when."

Monday, May 4, 2015

Cahokia's emergence and decline linked to Mississippi River flooding

 As with rivers, civilizations across the world rise and fall. Sometimes, the rise and fall of rivers has something to do with it.

At Cahokia, the largest prehistoric settlement in the Americas north of Mexico, new evidence suggests that major flood events in the Mississippi River valley are tied to the cultural center's emergence and ultimately, to its decline.

Publishing today [5/4/15] in the Proceedings of the National Academy of Sciences, a research team led by UW-Madison geographers Samuel Munoz and Jack Williams provides this evidence, hidden beneath two lakes in the Mississippi floodplain.

Sediment cores from these lakes, dating back nearly 2,000 years, provide evidence of at least eight major flood events in the central Mississippi River valley that could help explain the enigmatic rise and fall of Cahokia, near present-day St. Louis.

While the region saw frequent flood events before A.D. 600 and after A.D. 1200, Cahokia rose to prominence during a relatively arid and flood-free period and flourished in the years before a major flood in 1200, the study reveals. Cahokia, in the midst of political instability and population decline at this time, was completely abandoned by the year 1400.

While drought has traditionally been implicated as one of several factors leading to the decline of many early agricultural societies in North America and around the world, the findings of this study present new ideas and avenues for archaeologists and anthropologists to explore.

"We are not arguing against the role of drought in Cahokia's decline but this presents another piece of information," says Samuel Munoz, a Ph.D. candidate in geography and the study's lead author.

"It also provides new information about the flood history of the Mississippi River, which may be useful to agencies and townships interested in reducing the exposure of current landowners and townships to flood risk," says Williams, a professor of geography and director of the Nelson Institute for Environmental Studies Center for Climatic Research.

However, Munoz never intended to make these findings. In fact, "it was kind of an accident," he says.

Originally, Munoz was looking for the signals of prehistoric land use on ancient forests. He chose to study Cahokia because it was such a large site and is famous for its large earthen mounds. At one point, tens of thousands of people lived in and around Cahokia. If there was anywhere that ancient peoples would have altered the landscapes of the past, it was in the area around Cahokia.

The team went to Horseshoe Lake, near the six-square-mile city's center, and collected cores of lake mud -- all the stuff that settles to the bottom -- to look for pollen and other fossils that document environmental change. Lakes are "sediment traps" that can capture and record past environmental changes, much like the rings of a tree.

"We had these really strange layers in the core that didn't have any pollen and they had a really odd texture," Munoz says. "In fact, one of the students working with us called it 'lake butter.'"

They asked around, talked to colleagues, and checked the published literature. The late Jim Knox, who spent his 43-year career as a geography professor at UW-Madison, suggested to Munoz that he think about flooding, which can disrupt the normal deposition of material on lake bottoms and leave a distinct signature.

The team used radiocarbon dating of plant remains and charcoal within the core to create a timeline extending back nearly two millennia. In so doing, they established a record of eight major flood events at Horseshoe Lake during this time, including the fingerprint left by a known major flood in 1844.

To validate the findings, the team also collected sediments from Grassy Lake, roughly 120 miles downstream from Cahokia, and found the same flood signatures (Grassy Lake is younger than Horseshoe Lake, so its sediments captured only the five most recent flood events).

The new findings show that floods were common in the region between A.D. 300 and 600. Meanwhile, the earliest evidence of more agricultural settlement appears along the higher elevation slopes at the edge of the central Mississippi River floodplain around the year 400. But by 600, when flooding diminished and the climate became more arid, archaeological evidence shows that people had moved down into the floodplain, began to increase in population, and farmed more intensively.

"Rarely do you get such fortuitous opportunities where you have these nice sedimentary records next to an archaeological site that's so well studied," says Munoz.

Early on in the study, Munoz and Williams enlisted the help of Sissel Schroeder, a UW-Madison professor of anthropology whose doctoral studies focused on the Cahokia area. Schroeder accompanied the Geography Department scientists out in the field and helped provide historical and archaeological context.

She explains that while there has been little archaeological evidence to suggest flooding at Cahokia, it can't be ruled out. It's possible, she says, that researchers have simply missed the signals.

For example, archaeologists know that around the year 900, people in the area began to cultivate maize and their population exploded, shown by the number and size of buildings and structures that sprang up in the region. Archaeologists often think of Cahokia as a chiefdom, with a hierarchy of smaller settlements that spread out from the city, much like the small county seats that surround the major government centers we're familiar with today, Schroeder explains.

But around 1200, coinciding with a major flood fingerprint in Munoz's sediments, the population began to decline along with other shifts in the archaeological record.

"We see some important changes in the archaeology of the site at this time, including a wooden wall that is built around the central precinct of Cahokia," says Schroeder. "There are shifts in craft production, house size and shape, and other signals in material production that indicate political, social and economic changes that may be associated with social unrest."

Cahokia appears to have fractured and its people began to migrate to other parts of North America. By 1400, after the arid conditions that suppressed large floods and favored Cahokia's rise had passed, it was deserted.

While many factors likely contributed to Cahokia's decline -- from extreme events like droughts or floods, to the inherent instability archaeologists and anthropologists have documented in other chiefdom societies -- a major flooding event could have been the proverbial last straw.

"It would have had a particularly destabilizing effect after hundreds of years without large floods," Schroeder says.

In order to deposit sediments into Horseshoe and Grassy Lakes, the Mississippi River would have had to rise 10 meters (about 33 feet) above its base elevation at St. Louis, according to models run in the study. This substantial flood would have inundated the region's crops, impacted essential food stores, and created agricultural shortfalls.

Food and other essential resources would have been currency in a civilization like Cahokia and could have been leveraged for political gains following a flood of the scale documented in the study.

"We hope archaeologists can start integrating these flood records into their ideas of what happened at Cahokia and check for evidence of flooding," says Munoz, who plans to continue studying flood records in lakes around the country once he graduates this year.

The study also provides new information about the river's behavior in the central Mississippi Valley, Williams says. Relatively little is currently known about its prehistoric flood cycle but the study suggests that major floods like those in 1844 or 1993 happened every century or two prior to European settlement and intervention, with the exception of the unusually arid years that facilitated Cahokia's growth.

"We have managed the river so much to prevent floods from happening, we don't have a good baseline for how the river behaves without human modification," he says. "This may help us understand not only how it once behaved, but how it may behave in the future."