New hominid species discovered and described in South Africa

*

A team led by Professor Lee Berger, a renowned palaeoanthropologist from the University of the Witwatersrand, Johannesburg (aka Wits University) have described and named a new species of hominid, Australopithecus sediba, almost two million years old, which was discovered in the Cradle of Humankind World Heritage Site, 40 kilometres out of Johannesburg, South Africa.

Two papers related to this find, authored by Prof. Lee Berger and Prof. Paul Dirks respectively, will be published in the journal Science on Friday, 9 April 2010.

"Sediba, which means natural spring, fountain or wellspring in Sotho, one of the 11 official languages of South Africa, was deemed an appropriate name for a species that might be the point from which the genus Homo arises," comments Berger. "I believe that this is a good candidate for being the transitional species between the southern African ape-man Australopithecus africanus (like the Taung Child and Mrs. Ples) and either Homo habilis or even a direct ancestor of Homo erectus (like Turkana Boy, Java man or Peking man)."

The fossils, a juvenile male and an adult female, were deposited within a single debris flow and occur together in a near articulated state in the remains of a deeply eroded cave system. The sedimentary and geological context indicates that the timing of their death was closely related and occurred shortly before the debris flow carried them to their place of burial.

The species has long arms, like an ape, short powerful hands, a very advanced pelvis (hip bone) and long legs capable of striding and possibly running like a human. It is likely that they could have climbed. "It is estimated that they were both about 1.27 metres, although the child would certainly have grown taller. The female probably weighed about 33 kilograms and the child about 27 kilograms at the time of his death," adds Prof. Berger. "The brain size of the juvenile was between 420 and 450 cubic centimetres, which is small (when compared to the human brain of about 1200 to 1600 cubic centimetres) but the shape of the brain seems to be more advanced than that of australopithecines."

Through a combination of faunal, U-Pb and palaeomagnetic dating techniques, the age of the rocks encasing the fossils has been determined at 1.95-1.78 Ma. . Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time.

The skeletons were found amongst the articulated skeletons of a sabre-toothed cat, antelope, mice and rabbits. They are preserved in a hard, concrete like substance known as calcified clastic sediment that formed at the bottom of what appears to be a shallow underground lake or pool that was possibly about 50 metres tall about 1,9 million years ago.

Fossil preparators have worked arduously over the last two years to extract the bones from the rock. About 60 leading scientists from around the world and tens of students have had the opportunity to work on these amazing fossils. The most sophisticated scanning technology has been used to unveil the secrets of the past.

The site continues to be explored and without a doubt there are more groundbreaking discoveries to come forth. In celebration of this find, the children of South Africa have been invited to develop a common name for the juvenile skeleton. The fossils are owned by the people of South Africa, and curated by the University of the Witwatersrand, Johannesburg.



FREQUENTLY ASKED QUESTIONS
BY PROF. LEE BERGER


What does Australopithecus sediba mean?
Australopithecus means "southern ape", after the genus of the Taung child, named by Prof. Raymond Dart, also from the University of the Witwatersrand, Johannesburg. Sediba means natural spring, fountain or wellspring in Sotho, an appropriate name for a species that might be the point from which the genus Homo arises.

What is a hominid/hominin?
A hominid is a member of the taxonomic family that includes humans, chimpanzees, gorillas and their extinct ancestors. Hominins are members of the human branch after the human lineage split from that of chimpanzees, and thus include living humans and extinct human ancestors, such as the Australopiths. Hominins are characterised by bipedal locomotion, although this may not have been the case for the very earliest members of the group, and relatively small canine teeth. Later members of this group (those in the genus, Homo) are characterised by larger brains than those of living apes like chimpanzees, bonobos, gorillas, orangutans and gibbons.

How were the fossils dated?
They were dated using a variety of methods including Uranium-Lead, palaeomagnetic and faunal dating systems. Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time.

How were the individuals preserved?
The site where the fossils were discovered is technically the infill of a de-roofed cave that was about 50 metres underground 1.9 million years ago. The individuals appear to have fallen, along with other animals, into a deep cave, landing up on the floor for a few days or weeks. The bodies were then washed into an underground lake or pool probably pushed there by a large rainstorm. They did not travel far, maybe a few metres, where they were solidified, as if thrown into quick setting concrete. The rock they are preserved in is called calcified clastic sediment. Over the past 1.9 million years the land has eroded to expose the fossil bearing sediments.

Did they die at the same time, or was it a catastrophe?
The hominin skeletons were found with the bones either in partial articulation or in close anatomical association, which suggests that both bodies were only partially decomposed at the time of deposition in the lower chamber. This further suggests that they died very close in time to each other, either at the same time, or hours, days or weeks apart.

How old is the child?
The juvenile is around 10 – 13 years old in human developmental terms. He was probably a bit younger in actual age (perhaps as young as eight or nine or so) as he is likely to have matured faster than humans. The age estimate is based on modern human standards by which the eruption stages of the teeth are evaluated and the degree of development of the growth centres of the bones.

How old is the female skeleton?
Based on the extreme wear of her teeth, she is probably at least in her late twenties or early thirties.

Did she have children?
It is likely that a female Australopith of her age would have had children.

How do you know the child is a male?
There are features of the face that help us determine that the child is a male. The muscles of the child are larger than that of the other skeleton, even though it is a child. There are also features of the pelvis that we can use to determine that it is a male.

How does this find relate to Lucy?
Australopithecus sediba is approximately a million years younger than Lucy. Some scientists feel that Lucy's species, Au. Afarensis, gave rise to Au. africanus and Lee et al are suggesting that Au. africanus or something similar, gave rise to Au. Sediba.

How do you know that it is a new species?
The team compared the skeletons with all the remains of fossil hominids that have been discovered and in many ways they are absolutely unique from any fossil species found.

Why is this not the genus Homo?
The fossils have an overall body plan that is like that of other Australopiths – they have small brains, relatively small bodies and long and seemingly powerful arms. They do have some features in the skull and pelvis that are found in members of the genus Homo but not in other Australopiths. However, given the small brains and Australopith-like upper body, the team felt that keeping this species in the genus Australopithecus was the conservative thing to do.

What about Homo habilis?
Our study indicates that Australopithecus sediba may be a better ancestor of Homo erectus and it may certainly help to clear up some of this "muddle in the middle".

Why is there still rock attached to the child's skull?
Due to the fragility of the base of the cranium of the specimen and to preserve part of the adhering matrix for future research, the team has decided to leave the specimen partially in rock. The team has been able to visualise this hidden part using scanning technology.

Ancient Assyrian Treaty Discovered

A cache of cuneiform tablets unearthed by a team led by a University of Toronto archaeologist has been found to contain a largely intact Assyrian treaty from the early 7th century BCE.

"The tablet is quite spectacular. It records a treaty — or covenant — between Esarhaddon, King of the Assyrian Empire and a secondary ruler who acknowledged Assyrian power. The treaty was confirmed in 672 BCE at elaborate ceremonies held in the Assyrian royal city of Nimrud (ancient Kalhu). In the text, the ruler vows to recognize the authority of Esarhaddon's successor, his son Ashurbanipal," said Timothy Harrison, professor of near eastern archaeology in the Department of Near & Middle Eastern Civilizations and director of U of T's Tayinat Archaeological Project (TAP).

"The treaties were designed to secure Ashurbanipal's accession to the throne and avoid the political crisis that transpired at the start of his father's reign. Esarhaddon came to power when his brothers assassinated their father, Sennacherib."

The 43 by 28 centimetre tablet — known as the Vassal Treaties of Esarhaddon — contains about 650 lines and is in a very fragile state. "It will take months of further work before the document will be fully legible," added Harrison. "These tablets are like a very complex puzzle, involving hundreds of pieces, some missing. It is not just a matter of pulling the tablet out, sitting down and reading. We expect to learn much more as we restore and analyze the document."

The researchers hope to glean information about Assyria's imperial relations with the west during a critical period, the early 7th century BCE. It marked the rise of the Phrygians and other rival powers in highland Anatolia — now modern-day Turkey — along the northwestern frontier of the Assyrian empire, and coincided with the divided monarchy of Biblical Israel, as well as an era of increased contact between the Levantine peoples of the Eastern Mediterranean and Egypt, as well as the Greeks of the Aegean world.

The cache of tablets — which date back to the Iron Age — were unearthed in August 2009 during excavations at the site of an ancient temple at Tell Tayinat, located in southeastern Turkey. A wealth of religious paraphernalia — including gold, bronze and iron implements, libation vessels and ornately decorated ritual objects — was also uncovered.

Archaeologists uncover land before wheel; site untouched for 6,000 years

Previously unexcavated site reveals clues about world's first cities

A team of archaeologists from the University of Chicago's Oriental Institute, along with a team of Syrian colleagues, is uncovering new clues about a prehistoric society that formed the foundation of urban life in the Middle East prior to invention of the wheel.

The mound of Tell Zeidan in the Euphrates River Valley near Raqqa, Syria, which had not been built upon or excavated for 6,000 years, is revealing a society rich in trade, copper metallurgy and pottery production. Artifacts recently found there are providing more support for the view that Tell Zeidan was among the first societies in the Middle East to develop social classes according to power and wealth.

Tell Zeidan dates from between 6000 and 4000 B.C., and immediately preceded the world's first urban civilizations in the ancient Middle East. It is one of the largest sites of the Ubaid culture in northern Mesopotamia.

Thus far, archaeologists have unearthed evidence of this society's trade in obsidian and production and development of copper processing, as well as the existence of a social elite that used stone seals to mark ownership of goods and culturally significant items.

"The project addresses questions not only of how such societies emerged but how they were sustained and flourished," said John Yellen, program director for archaeology in the National Science Foundation's (NSF) Social, Behavioral & Economic Sciences directorate. NSF supports the University of Chicago's research.

Covering about 31 acres, Tell Zeidan was situated where the Balikh River joins the Euphrates River in modern-day Syria. The location was at the crossroads of major, ancient trade routes in Mesopotamia that followed the course of the Euphrates River valley. The Ubaid period lasted from about 5300 to 4000 B.C.

"This enigmatic period saw the first development of widespread irrigation, agriculture, centralized temples, powerful political leaders and the first emergence of social inequality as communities became divided into wealthy elites and poorer commoners," said Gil Stein, director of the Oriental Institute and a leader of the expedition.

"The research also is important because it provides insight into how complex societies, based on linkages which extended across hundreds of miles, developed," said Yellen, noting the distance travelled for raw materials needed for many of the Tell Zeidan artifacts.

For example, copper ore was carried by workers from sources near modern-day Diyarbakir, Turkey, about 185 to 250 miles away, then smelted at Tell Zeidan to produce metal tools and other implements.

One of the most remarkable finds was a stone stamp seal depicting a deer, Stein said. The seal was about two inches by two-and-a-half inches and was carved from a red stone not native to the area. A similar seal design was found 185 miles to the east near Mosul in northern Iraq.

"The existence of very elaborate seals with near-identical motifs at such widely distant sites suggests that in this period, high-ranking elites were assuming leadership positions across a very broad region, and those dispersed elites shared a common set of symbols and perhaps even a common ideology of superior social status," said Stein.

Stein said Tell Zeidan may have been one of the largest Ubaid temple towns in northern Mesopotamia, and that it was as large or larger than any previously known contemporary Ubaid towns in the southern alluvial lowlands of the Tigris and Euphrates rivers in what is today southern Iraq. However, because the site was not occupied after about 4,000 B.C., the prehistoric strata of Tell Zeidan are immediately accessible beneath the modern-day ground surface instead of being buried beneath layers of deposits from later periods.

"This means that, for the first time, archaeologists can excavate broad areas of an Ubaid temple town to understand how a proto-urban community actually functioned in the sixth-fifth millennia B.C.," Stein said.

The new excavations Tell Zeidan reveal the emergence of an elite that possessed the political power necessary for communities to move from self-sufficient village life to societies dependent on trade and capable of acquiring luxury goods, Stein said.

"The two-millennium-long occupation spans four key periods: two phases of the late Copper Age on top, the Ubaid period in the middle and the Halaf period at the bottom," Stein said.

The excavations so far show that the transitions between these periods were peaceful, including the period in which the influence of the Ubaid culture spread from its south Mesopotamian homeland up the Euphrates River into north Syria.

The team found obsidian blades and chips wasted during the production of the blades. The high-quality volcanic glass had to be brought to the community from sources 250 miles away in what is now Turkey. The greenish-black color and chemical composition show that it came from mines in the eastern part of the country.

The people in Tell Zeidan also had access to copper ore from sources near modern-day Diyarbakir, Turkey, about 185 to 250 miles away. Those materials were smelted at Tell Zeidan to produce metal tools that represent the most advanced technology of the fifth millennium B.C. People must have transported the material on their backs, however, as Tell Zeidan flourished at a time before donkeys were domesticated.

The wealth of the community came from irrigation-based agriculture, trade and manufacturing. "We found flint sickle blades everywhere, easily recognizable from the glossy sheen where they had been polished by the silica in the stems of the wheat that they were used to harvest," Stein said. The people used bitumen, a tar substance obtained from pits 43 miles away, to secure the blades onto handles.

Along with the advanced technology, a wealthy ruling class and individual identification by stamp seals, the people at Tell Zeidan also built large public structures of mud bricks.
Stein said the location's potential for further discoveries is so great the project is likely to last for decades.

Natural explanation for the 10 plagues

*
Complete article

Researchers believe they have found evidence of real natural disasters on which the ten plagues of Egypt, which led to Moses freeing the Israelites from slavery in the Book of Exodus in the Bible, were based.

But rather than explaining them as the wrathful act of a vengeful God, the scientists claim the plagues can be attributed to a chain of natural phenomena triggered by changes in the climate and environmental disasters that happened hundreds of miles away.

Archaeologists now widely believe the plagues occurred at an ancient city of Pi-Rameses on the Nile Delta, which was the capital of Egypt during the reign of Pharaoh Rameses the Second, who ruled between 1279BC and 1213BC.

The city appears to have been abandoned around 3,000 years ago and scientists claim the plagues could offer an explanation.

Climatologists studying the ancient climate at the time have discovered a dramatic shift in the climate in the area occurred towards the end of Rameses the Second's reign.

The scientists believe this switch in the climate was the trigger for the first of the plagues...

An Archaeological Mystery in a Half-ton Lead Coffin

In the ruins of a city that was once Rome's neighbor, archaeologists last summer found a 1,000-pound lead coffin.

Who or what is inside is still a mystery, said Nicola Terrenato, the University of Michigan professor of classical studies who leads the project---the largest American dig in Italy in the past 50 years.

The sarcophagus will soon be transported to the American Academy in Rome, where engineers will use heating techniques and tiny cameras in an effort to gain insights about the contents without breaking the coffin itself.

"We're very excited about this find," Terrenato said. "Romans as a rule were not buried in coffins to begin with and when they did use coffins, they were mostly wooden. There are only a handful of other examples from Italy of lead coffins from this age---the second, third or fourth century A.D. We know of virtually no others in this region."

This one is especially unusual because of its size.

"It's a sheet of lead folded onto itself an inch thick," he said. "A thousand pounds of metal is an enormous amount of wealth in this era. To waste so much of it in a burial is pretty unusual."

Was the deceased a soldier? A gladiator? A bishop? All are possibilities, some more remote than others, Terrenato said. Researchers will do their best to examine the bones and any "grave goods" or Christian symbols inside the container in an effort to make a determination.

"It's hard to predict what's inside, because it's the only example of its kind in the area," Terrenato said. "I'm trying to keep my hopes within reason."

Human remains encased in lead coffins tend to be well preserved, if difficult to get to. Researchers want to avoid breaking into the coffin. The amount of force necessary to break through the lead would likely damage the contents. Instead, they will first use thermography and endoscopy. Thermography involves heating the coffin by a few degrees and monitoring the thermal response. Bones and any artifacts buried with them would have different thermal responses, Terrenato said. Endoscopy involves inserting a small camera into the coffin. But how well that works depends on how much dirt has found its way into the container over the centuries.

If these approaches fail, the researchers could turn to an MRI scan---an expensive option that would involve hauling the half-ton casket to a hospital.

The dig that unearthed this find started in summer 2009 and continues through 2013. Each year, around 75 researchers from around the nation and world, including a dozen U-M undergraduate students, spend two months on the project at the ancient city of Gabii (pronounced "gabby").

The site of Gabii, situated on undeveloped land 11 miles east of Rome in modern-day Lazio, was a major city that pre-dates Rome but seems to have waned as the Roman Empire grew.

Studying Gabii gives researchers a glimpse into pre-Roman life and offers clues to how early Italian cities formed. It also allows them broader access to more substantial archaeological layers or strata. In Rome, layers of civilization were built on top of each other, and archaeologists are not able or allowed to disturb them.

"In Rome, so often, there's something in the way, so we have to get lucky," Terrenato said. "In Gabii, they should all be lucky spots because there's nothing in the way."

Indeed, Terrenato and others were surprised to find something as significant as this coffin so soon.

What mineral that might have been the key ingredient in the blue used to decorate "blue painted pottery"?

Pottery decorated in a distinctive pale blue color was in vogue in New Kingdom Egypt, particularly during the reign of Amenhotep III and Ramesses II. The pale blue is due to cobalt that may have been derived from a mineral mined at an oasis in the eastern Saharan desert. (Credit: Colin A. Hope/ Monash University)

Jennifer Smith, PhD, associate professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis, was belly crawling her way to the end of a long, narrow tunnel carved in the rock at a desert oasis by Egyptians who lived in the time of the pharaohs.

She was seeking an uncontaminated sample of a mineral that might have been the key ingredient in the blue used to decorate "blue painted pottery" popular among the Egyptian elite during the New Kingdom (1550 to 1079 BCE).

Colleague Colin A. Hope, an expert in blue painted pottery, had asked if she wouldn't help him pin down the source of the blue pigment by sampling and analyzing material fromt he mine.

Hope and Smith, together with Paul Kucera, a doctoral student at Monash University who first identified the mines, describe the pottery, the mines and the mineral in a chapter of Beyond the Horizon, a festschrift for the Egyptologist Barry A. Kemp,

'Generic geologist'

In the wastes of the eastern Sahara, nestled against the limestone escarpment that separates the desert from the Nile Valley, lies the Dakhleh Oasis. This fortunate spot, where deep water is able to reach the surface along fractures and faults under its own pressure, has been continuously inhabited for a very long time -- perhaps as long as 400,000 years.

During that period there were roughly four glacial cycles and, although Egypt itself was ice-free, the local climate oscillated from hyperarid to semi-arid as the Earth's orbital position drove changes in the location of the tropical rainfall belts.

Smith studies the impact of these climate fluctuations on ancient oasis dwellers.

But Smith is also the "generic geologist" as she puts it, for the Dakhleh Oasis Project, a long-term study of the oasis that covers the entire stretch of Dakhleh history, from the Neolithic through the Pharaonic, Roman, Islamic and modern settlements, and employs -- off and on -- more than 50 specialists.

"The dig house is open from November until March," Smith says.

As generic geologist, Smith was asked to help with a material-sourcing puzzle that she says was "way outside her period." During the 2007 season, Colin A. Hope, PhD, associate professor and director of the Center for Archaeology and Ancient History at Monash University in Australia, asked her whether a mineral found at the oasis could have been used to color the blue painted pottery.

It was a small question but an intriguing one.

Blue painted pottery

Most Egyptian pottery is undecorated, but during the New Kingdom, the period when Egypt is at the zenith of its power, a variety of pottery was elegantly decorated in a distinctive pale blue.

The pottery has been found at many sites in Egypt, and also in the Middle East and in Sudan.

The largest deposits, however, were found at New Kingdom sites in Egypt, including Malqata (the palace complex of Amenhotep III), Amarna (the remains of the city built by the Akenaten, the famous pharaoh who moved the capital from Thebes and established his own religion), the cemetary at Deir el-Medineh (the village where artisans who worked on the tombs in the Valley of the Kings during the New Kingdom lived), and the Great Temple of Amun (patron of kingship during the New Kingdom).

"Walking over some sites, it is only a matter of minutes before several shards of blue painted pottery or cobalt blue glass or faience can be collected," Hope, who has written extensively about the pottery, says.

Given the restricted use to which the pigment was put and the archeological sites where remnants were found, Hope believes it was probably available only to artisans associated with major royal residences.

The pale blue is distinguishable at a glance from the brilliant blues and blue-greens of the faience glazes common from the 3000 BC onward. Faience, probably most familiar in the form of the small statue of a hippo nicknamed William that is now in the collection of the Metropolitan Museum of Art in New York, was made by adding ground copper to ground quartz to create what ceramists today call Egyptian paste.

But it is difficult to create durable patterns with copper pigment on pottery, says Hope. "Copper-based pigments must be applied in thick layers and were added after firing, so they tended to flake off when an object was handled. Instead of copper, the colorant used on most of the blue painted pottery is cobalt, which was fired onto the pots.

Where did the cobalt-bearing mineral come from? Analysis of the paint showed that the cobalt was accompanied by trace amounts of zinc, nickel and manganese, a mixture of elements distinctive enough to serve as a chemical fingerprint.

The mines of Dakhleh

At the height of its power, the Egyptian administration of the Nile Valley sponsored mineral exploitation of the Valley and surrounding desert regions. As early as 1980, it was suggested that the cobalt might have come from the desert oases at Dakhleh and Kharga.

In the lower foothills of the oasis escarpment at the western end of Dakhleh, four mine shafts were meticulously hand-cut into the rock. Steps carved along the shafts allowed a safe descent. The shafts provided access to horizontal galleries, some as long as 15 meters, that followed horizontal veins of the mineral alum.

A few centimeters thick, the alum veins are fibrous, pale gray to pink in color and slightly astringent.

Alum is both the term for a specific compound and for a class of compounds, all of which contain two negatively charged sulfate groups and two chemical elements or groups bearing a positive charge. The specific compound is hydrated aluminum potassium sulfate but many other elements or groups can substitute for the aluminum and potassium, and cobalt is one of these.

Alum was probably exploited for a variety of purposes in ancient times, some having nothing to do with color. The Egyptians, for example, used alum both to whiten skins during tanning and to prepare cloth to absorb dye.

Alum is still used today in styptic pencils to stem bleeding and in recipes for pickling cucumbers. More recently, it has been in vogue as a "crystal deodorant" that is sold as more natural than older deodorant products.

Was the Dakhleh Oasis alum used as a general-purpose astringent, or did it have the same chemical fingerprint as the blue paint on the pottery?

Analyzing the alum

To find out, Smith needed to sample the alum and analyze its composition. "I wanted to get relatively unaltered samples," she says, "which is why I was crawling to the end of a gallery. The galleries were small enough you couldn't really crawl on your hand and knees: you had to belly crawl."

Smith brought the samples she collected back to Washington University where she ran them through a variety of sophisticated analytical instruments. "When we characterize a natural mineral," she says, "we want to know two things: its chemical composition and then how the elements that make it up are arranged, or its crystal structure."

In the case of the Dakhleh alum, the crystal structure was of little use because it would have been destroyed in preparing the paint. Only the composition could connect the alum to the pottery.

Smith's results showed that the alum did contain cobalt, although they weren't particularly rich in this element. The cobalt, however, was accompanied by trace amounts of manganese, nickel and zinc, the same mixture of elements found in the blue paint.

Surprised by the low concentration of cobalt, Smith wondered if the ancient artisans hadn't found a way to concentrate it on site. One sample she collected, a crust at the edge of a partially flooded mine shaft, had a higher cobalt content than the others. Because sulphate dissolves easily and the mines were much more likely to have been flooded in the past, she wondered whether the cobalt was mined not by chipping it out of the rock but instead by ladling water out of the mines and collecting the sediment left over when the water evaporated.

"But this is wild arm waving given the amount of data," Smith says.

This small exercise in archeological problem solving left her with a deep respect for the long-vanished miners.

"I look at all these different veins of sulfate and I don't know which are useful for which purposes without doing analyses, but they must have had ways of telling from observable properties which ones to mine. That's impressive," she says.

Did the first 'modern' human beings on the Iberian Peninsula interact with Nanderthals?

They were in the same area at the same time, but no evidence of interaction

Research carried out by a group of archaeologists from the Centre for Prehistoric Archaeological Heritage Studies of the Universitat Autònoma de Barcelona (CEPAP_UAB) at the Cova Gran site (Lleida) has contributed to stirring up scientific debate about the appearance of the first "modern" human beings on the Iberian Peninsula and their possible bearing on the extinction of the Neanderthals. The samples obtained at Cova Gran using Carbon 14 dating refer to a period of between 34,000 and 32,000 years in which this biological replacement in the Western Mediterranean can be located in time, although the study regards as relative the use of Carbon 14 for dating materials from the period of transition of the Middle to Upper Palaeolithic period( 40,000 and 30,000). The results also support the hypothesis that there was neither interaction nor coexistence between the two species.

Cova Gran is a large shelter discovered in 2002, located in the area of Les Avellanes-Santa Linya -La Noguera- and is one of the rare European archaeological sites to enable the study of what is known in Paleoanthropology as "transitions" or critical phases in which transformations and remodelling that are essential for reconstructing the history of our species can be detected.

The investigators from the UAB have worked on an area of 60 metres squared, excavating a large area which has enabled them to reconstruct the way in which the people who inhabited the shelter lived. This system of working is not usual in archaeology since excavations are generally restricted to smaller earth movements. They have been able to recover archaeological materials from the Middle Palaeolithic attributable to Homo neanderthalensis, and from the Upper Palaeolithic, which corresponds to Homo sapiens, separated by sterile strata of sediment which allows their differentiation.

The exceptional conditions of conservation of these archaeological remains, which have remained unaffected by biological and geological changes, have meant that the materials used by each of these species has been conserved without the need for significant earth movements, contrary to that which has been indicated in other archaeological sites. This detailed analysis of the tool remains recovered allows major differences to be observed in the way in which they were made, implying that they were made by different species.

This is something that has also been recognised in other sites in Western Europe, and it goes to strengthen the hypothesis that the two species neither lived together nor interacted with each other, although they may have lived in the same geographical area during the period from 40,000 to 30,000 years, which is generally referred to as the Middle/Upper Palaeolithic "transition".

Cova Gran was occupied successively by Neanderthals and "modern" humans in small groups of 15 to 20 people with a similar lifestyle: hunting, gathering, making tools for their daily activities and obtaining and processing food for which the use of fire was essential. In spite of this, each species used very different techniques and primary materials.

Among the remains found that are attributable to Homo sapiens are several perforated sea snail shells, generally considered to be an indicator of the distribution of the species throughout Africa, the Middle East and Western Europe. They also denote the existence of a symbolic language and cognitive capacities for which there is no evidence during the Middle Palaeolithic These objects indicate that Homo sapiens travelled widely across lands from the Mediterranean coast to the Pyrenean foothills, a distance of over 150 kilometres, although the researchers do not rule out the existence of social networks which would connect groups separated by large distances and through which these objects would circulate. If this were the case, the ornaments would be a key symbolic element in the social structure of this people and a clue to their identity.

The work also offers new data about the period in which the first representatives of the so-called "modern humans" appeared in the Iberian Peninsula and the extinction of the Neanderthals, a question that has generated some heated debate within the area of Paleoanthropology. The Carbon 14 dated samples in Cova Gran make references to a period of between 34,000 and 32,000 years in which this biological replacement in the Western Mediterranean can be located in time.

Notwithstanding, the study also discusses the validity of C14, the method habitually used to date archaeological remains from that period. Although C14 is a vital tool for dating archaeological sites, one conclusion to emerge from the study is that the period between 40 and 30 thousand years cannot be considered as "historic" years. This observation has rekindled the controversy that has existed for some time in archaeology about whether C14 is a totally reliable timepiece. The radioactive isotope regularly disintegrates but from 30,000 years its presence in samples is residual and, in many cases, the samples have been exposed to processes of change that are difficult to identify. The researchers argue that much of the data that is usually obtained in studies of this period may correspond to samples that have been contaminated or have been treated in laboratories using methods that have failed to detect this type of problem. Currently improvements are being developed which it is hoped will eliminate this uncertainty.

The Cova Gran site covers a total surface area of 2,500 metres squared and contains an important archaeological heritage. Future excavations will enable more profound investigations into how modern humans settled in the Iberian Peninsular and their evolution over the last 40,000 years.