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."

Tuesday, April 28, 2015

Iinnovative hunting weapons carried by humans from Asia did not cause the demise of Neanderthals


The demise of Neanderthals may have nothing to do with innovative hunting weapons carried by humans from west Asia, according to a new study published in the Journal of Human Evolution. The researchers, from Nagoya University and The University of Tokyo, Japan, say their findings mean that we may need to rethink the reasons humans survived Neanderthals - and that we may not have behaved as differently as we thought.

The researchers looked at innovative stone weapons used by humans about 42,000-34,000 years ago. Traditionally, anthropologists believed that innovation in weapons enabled humans to spread out of Africa to Europe. However, the new study suggests that the innovation was not a driving force for humans to migrate into Europe as previously thought - they were no better equipped than the Neanderthals.

"We're not so special, I don't think we survived Neanderthals simply because of technological competence," said Dr. Seiji Kadowaki, first author of the study from Nagoya University, Japan. "Our work is related to the processes behind the global spread of modern humans, and specifically the cultural impact of the modern humans who migrated to Europe."

Anatomically modern humans expanded the geographic area they inhabited out of Africa during a period of time 55,000-40,000 years ago - this event made a huge impact on the biological origin of people living today. There are other theories for the geographical spread of anatomically modern humans, but this is generally accepted as a major event in human history.

Previous models assumed that anatomically modern humans - our direct ancestors - were special in the way they behaved and thought. These models considered technological and cultural innovation as the reason humans survived and Neanderthals did not.

There has always been a big question around the demise of the Neanderthals - why did they disappear when humans survived? We have a similar anatomy, so researchers traditionally thought there must have been differences in the way Neanderthals and humans behaved. The new study suggests that humans moved from west Asia to Europe without a big change in their behavior.

The researchers studied stone tools that were used by people in the Early Ahmarian culture and the Protoaurignacian culture, living in south and west Europe and west Asia around 40,000 years ago. They used small stone points as tips for hunting weapons like throwing spears. Researchers previously considered these to be a significant innovation - one that helped the humans migrate from west Asia to Europe, where Neanderthals were living.

However, the new research reveals a timeline that doesn't support this theory. If the innovation had led to the migration, evidence would show the stone points moving in the same direction as the humans. But at closer inspection, the researchers showed the possibility that the stone points appeared in Europe 3,000 years earlier than in the Levant, a historical area in west Asia. Innovation in hunting weapons can be necessary, but it's not always associated with migration - populations can spread without technological innovations.

"We looked at the basic timeline revealed by similar stone points, and it shows that humans were using them in Europe before they appeared in the Levant - the opposite of what we'd expect if the innovation had led to the humans' migration from Africa to Europe," said Dr. Kadowaki.

"Our new findings mean that the research community now needs to reconsider the assumption that our ancestors moved to Europe and succeeded where Neanderthals failed because of cultural and technological innovations brought from Africa or west Asia."

By re-examining the evidence, the researchers showed that the comparable stone weapons appeared in Europe around 42,000 years ago, and in the Levant 39,000 years ago. They believe the timings imply several new scenarios about the migration of modern humans into Europe. For example, they are likely to have migrated to Europe much earlier, and developed the tools there.

"We're very excited about our new model. We think the causes of human evolution are more complicated than just being about technology. Now that we've re-examined the traditional model about the northern migration route to Europe, we are planning to re-evaluate the model on the southern migration route - from East Africa to South Asia" said Dr. Kadowaki

Monday, April 27, 2015

Archaeologists discount evidence purportedly showing North America was colonized by ice age Europeans


There has long been a debate among scholars about the origins of the first inhabitants of North America. The most widely accepted theory is that sometime before 14,000 years ago, humans migrated from Siberia to Alaska by means of a "land bridge" that spanned the Bering Strait. However, in the 1990s, a small but vocal group of researchers proposed that North America was first settled by Upper Paleolithic people from Europe, who moved from east to west through Greenland via a glacial "ice bridge." Now, researchers at the University of Missouri, working with colleagues the Cleveland Museum of Natural History and elsewhere, have definitively disproved the ice bridge theory.

One piece of evidence that advocates of the ice bridge theory rely on comes from the Chesapeake Bay. In the early 1970s, the crew of a scallop trawling vessel, Cinmar, was operating off the coast of Virginia when it hit a snag and pulled up an ancient stone blade, along with pieces of a mastodon skeleton. Since radiocarbon dating isn't available on inanimate objects, scholars correlated the date of the blade with the mastodon, which they could date at more than 22,000 years old.

"For more than two decades, proponents of the ice bridge theory have pointed to similarities between North American stone blades such as the one allegedly dredged from the Chesapeake and blades left by Solutrean foragers in western Europe," said Michael J. O'Brien, a professor of anthropology at MU and dean of the College of Arts and Science. "We know, however, that Solutrean culture began around 22,000 to 17,000 years ago, which is later than North American dates pointed to by ice bridge theorists as proof that Solutrean people populated North America. That includes the date from the Cinmar mastodon."

Mizzou scholars, including O'Brien's postdoctoral student, Metin Eren, and graduate student Matthew Boulanger, point to the lack of first-hand accounts from the crew of the Cinmar who recovered the blade and mastodon remains. All published accounts were first written by proponents of the Solutrean hypothesis. According to a telephone interview of the ship's captain, he "took particular note of the water depth" and "plotted the area on his navigation charts."

"While the interview indicates that the Cinmar captain took detailed notes, researchers never indicated that they actually observed the charts," O'Brien said. "In fact, captains keep 'hang logs' in which they record readings when they hit obstructions on the ocean floor. We reviewed countless snag reports from the Bay and the time frame when the snag should've occurred and didn't find anything to corroborate the story. One of the most famous snags of all time--when the crew pulled up a mastodon--and it's just not reported."

While researching the history of the stone tool, its recovery and whereabouts for more than 40 years, the team also found inconsistencies with the origins and the ownership of the ship itself. The research team found that discrepancies in photographs of the Cinmar, the size of the ship and where it was assembled all point to contradictions in key pieces of the ice bridge theory.

"Until inaccuracies are cleared up, there really is no reason to accept the find as evidence of anything connected with the early peopling of North America," O'Brien said.

The study, "The Cinmar discovery and the proposed pre-Late Glacial Maximum occupation of North America," recently was published in the Journal of Archaeological Science: Reports.

Wednesday, April 15, 2015

Complex cognition shaped the Stone Age hand axe


The ability to make a Lower Paleolithic hand axe depends on complex cognitive control by the prefrontal cortex, including the "central executive" function of working memory, a new study finds.

PLOS ONE published the results, which knock another chip off theories that Stone Age hand axes are simple tools that don't involve higher-order executive function of the brain.

"For the first time, we've showed a relationship between the degree of prefrontal brain activity, the ability to make technological judgments, and success in actually making stone tools," says Dietrich Stout, an experimental archeologist at Emory University and the leader of the study. "The findings are relevant to ongoing debates about the origins of modern human cognition, and the role of technological and social complexity in brain evolution across species."

The skill of making a prehistoric hand axe is "more complicated and nuanced than many people realize," Stout says. "It's not just a bunch of ape-men banging rocks together. We should have respect for Stone Age tool makers."

The study's co-authors include Bruce Bradley of the University of Exeter in England, Thierry Chaminade of Aix-Marseille University in France; and Erin Hecht and Nada Khreisheh of Emory University.

Stone tools - shaped by striking a stone "core" with a piece of bone, antler, or another stone - provide some of the most abundant evidence of human behavioral change over time. Simple Oldowan stone flakes are the earliest known tools, dating back 2.6 million years. The Late Acheulean hand axe goes back 500,000 years. While it's relatively easy to learn to make an Oldowan flake, the Acheulean hand axe is harder to master, due to its lens-shaped core tapering down to symmetrical edges.

"We wanted to tease apart and compare what parts of the brain were most actively involved in these stone tool technologies, particularly the role of motor control versus strategic thinking," Stout says.

The researchers recruited six subjects, all archeology students at Exeter University, to train in making stone tools, a skill known as "knapping." The subjects' skills were evaluated before and after they trained and practiced. For Oldowan evaluations, subjects detached five flakes from a flint core. For Acheulean evaluations, they produced a tool from a standardized porcelain core.

At the beginning, middle and end of the 18-month experiment, subjects underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) scans of their brains while they watched videos. The videos showed rotating stone cores marked with colored cues: A red dot indicated an intended point of impact, and a white area showed the flake predicted to result from the impact. The subjects were asked the following questions:

"If the core were struck in the place indicated, is what you see a correct prediction of the flake that would result?"

"Is the indicated place to hit the core a correct one given the objective of the technology?"

The subjects responded by pushing a "yes" or "no" button.

Answering the first question, how a rock will break if you hit it in a certain place, relies more on reflexive, perceptual and motor-control processes, associated with posterior portions of the brain. Stout compares it to the modern-day rote reflex of a practiced golf swing or driving a car.

The second question - is it a good idea to hit the core in a certain spot if you want to make a hand axe - involves strategic thinking, such as planning the route for a road trip. "You have to think about information that you have stored in your brain, bring it online, and then make a decision about each step of the trip," Stout says.

This so-called executive control function of the brain, associated with activity in the prefrontal cortex, allows you to project what's going to happen in the future and use that projection to guide your action. "It's kind of like mental time travel, or using a computer simulation," Stout explains. "It's considered a high level, human cognitive capacity."

The researchers mapped the skill level of the subjects onto the data from their brain scans and their responses to the questions.

Greater skill at making tools correlated with greater accuracy on the video quiz for predicting the correct strategy for making a hand axe, which was itself correlated with greater activity in the prefrontal cortex. "These data suggest that making an Acheulean hand axe is not simply a rote, auto pilot activity of the brain," Stout says. "It requires you to engage in some complicated thinking."

Most of the hand axes produced by the modern hands and minds of the study subjects would not have cut it in the Stone Age. "They weren't up to the high standards of 500,000 years ago," Stout says.

A previous study by the researchers showed that learning to make stone tools creates structural changes in fiber tracts of the brain connecting the parietal and frontal lobes, and that these brain changes correlated with increases in performance. "Something is happening to strengthen this connection," Stout says. "This adds to evidence of the importance of these brain systems for stone tool making, and also shows how tool making may have shaped the brain evolutionarily."

Stout recently launched a major, three-year archeology experiment that will build on these studies and others. Known as the Language of Technology project, the experiment involves 20 subjects who will each devote 100 hours to learning the art of making a Stone Age hand axe, and also undergo a series of MRI scans. The project aims to hone in whether the brain systems involved in putting together a sequence of words to make a meaningful sentence in spoken language overlap with systems involved in putting together a series of physical actions to reach a meaningful goal.


Neanderthals manipulated the bodies of adults and children shortly after death


Neanderthals from the French region of Poitou-Charentes cut, beat and fractured the bones of their recently deceased companions, as revealed by the fossil remains of two adults and a child found at the Marillac site. These manipulations have been observed at other Neanderthal sites, but scientists still do not know whether they did this for food or ceremony.

Since the Marillac site in France was unearthed, the discovery of fossil remains of animals (90% belonging to reindeer), humans and Mousterian tools has enabled the site to be identified as a hunting area for Neanderthals (Homo neanderthalensis). But the most surprising thing about the site is the presence of a large quantity of bone remains of these hominids, many of which are yet to be analysed.

Now, a study published in the American Journal of Physical Anthropology has for the first time analysed the fragments of three individuals found between 1967 and 1980 at the French site dating back some 57,600 years. These are an incomplete diaphysis (middle part of long bones) of a right radius, another of a left fibula and the majority of a right femur. The latter belonged to a child.

When compared to the remains of other Neanderthals and modern humans, the scientists confirm not only the strength and rounded form of Neanderthal bones, but they also identify on the three bones manipulations made very shortly after the individuals' death.

As MarĂ­a Dolores Garralda, professor at the Complutense University of Madrid, a researcher at the University of Bordeaux in France and the main author of the study, explains to SINC: "Some Neanderthal groups cut and tore apart child or adult corpses shortly after death (perimortem) using lytic instruments."

Cuts, beating, fracturing and stains

The femur fragment, which appears to be from a child who died at the age of 9 or 10, shows two large cut marks half a centimetre apart. From its state of preservation, the researchers suggest that the bone was fractured when still fresh with the aim of separating the upper and lower extreme of the femur, where the joints are located.

"The upper edge exhibits marks of a "post-mortem" impact with conchoidal markings (those that does not follow natural separation positions)," the study sets out. The lower region possesses a clear, oblique spiral break which seems to have occurred while the bone was fresh.

"Given the morphology of the fractures, it may be that the body of this child was manipulated shortly after death. The right leg received a series of blows that fractured the femur, and the cut marks identified are anthropic in nature; in other words, there is no visible evidence of animal bites," Garralda notes.

The bones of the two adults show these and other markings. The fragment of the radius, possibly belonging to a man, also has small, fine cut marks made with flint tools shortly after death. "The most significant are three striations together crossing over each other while the bone was still fresh," the study describes.

As for the fibula, although the fresh fractures of both extremes can be seen, there are also signs of percussion at the lower end. But "there is no evidence of cuts or traces of carnivores' teeth," the researcher insists. Unlike to the other two fragments of bones analysed, the fibula fossil exhibits numerous manganese stains; manganese is a very abundant mineral in the cave which gives bones a black colour.

Cannibalism or rituals?

The team of scientists does not know why they did this: "They might have been rituals - still in the 21st century these continue in certain parts of the world - or for food - gastronomic cannibalism or due to need," asserts the expert, who remains cautious regarding the hypothesis of cannibalism, due to the large number of animal bones found on the site which could have been Neanderthals' food.

"To date we have been able to demonstrate these manipulations at several Neanderthal sites in Europe, which are of course much more recent, including in groups of contemporary humans, but we have not been able to demonstrate the consumption of human meat by Neanderthals (although this has indeed been done in other much more modern populations)," Garralda details.

In addition to these perimortem corporal manipulations carried out by members of the group, other bones found at the Marillac site, also fragmented, exhibit signs of gnawing or digestion by animals. "These markings and deformations are clearly distinguishable from those studied in the three Neanderthal diaphysis," the expert concludes.