Climatic fluctuations drove key events in human evolution

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Research at the University of Liverpool has found that periods of rapid fluctuation in temperature coincided with the emergence of the first distant relatives of human beings and the appearance and spread of stone tools.

Dr Matt Grove from the School of Archaeology, Classics and Egyptology reconstructed likely responses of human ancestors to the climate of the past five million years using genetic modelling techniques. When results were mapped against the timeline of human evolution, Dr Grove found that key events coincided with periods of high variability in recorded temperatures.

Dr Grove said: "The study confirmed that a major human adaptive radiation – a pattern whereby the number of coexisting species increases rapidly before crashing again to near previous levels - coincided with an extended period of climatic fluctuation. Following the onset of high climatic variability around 2.7 million years ago a number of new species appear in the fossil record, with most disappearing by 1.5 million years ago. The first stone tools appear at around 2.6 million years ago, and doubtless assisted some of these species in responding to the rapidly changing climatic conditions.

"By 1.5 million years ago we are left with a single human ancestor – Homo erectus. The key to the survival of Homo erectus appears to be its behavioural flexibility – it is the most geographically widespread species of the period, and endures for over one and a half million years. Whilst other species may have specialized in environments that subsequently disappeared – causing their extinction – Homo erectus appears to have been a generalist, able to deal with many climatic and environmental contingencies."

Dr Grove's research is the first to explicitly model 'Variability Selection', an evolutionary process proposed by Professor Rick Potts in the late 1990s, and supports the pervasive influence of this process during human evolution. Variability selection suggests that evolution, when faced with rapid climatic fluctuation, should respond to the range of habitats encountered rather than to each individual habitat in turn; the timeline of variability selection established by Dr Grove suggests that Homo erectus could be a product of exactly this process.

Linking climatic fluctuation to the evolutionary process has implications for the current global climate change debate. Dr Grove said: "Though often discussed under the banner term of 'global warming', what we see in many areas of the world today is in fact an increased annual range of temperatures and conditions; this means in particular that third world human populations, many living in what are already marginal environments, will face ever more difficult situations. The current pattern of human-induced climate change is unlike anything we have seen before, and is disproportionately affecting areas whose inhabitants do not have the technology required to deal with it."

The research is published in The Journal of Human Evolution and The Journal of Archaeological Science.

Ancient technology spread more slowly in the Americas than in Eurasia

Population groups in the Americas had less frequent exchanges than groups that fanned out over Europe and Asia

How modern-day humans dispersed on the planet and the pace of civilization-changing technologies that accompanied their migrations are enduring mysteries. Scholars believe ancient peoples on Europe and Asia moved primarily along east-west routes, taking advantage of the relative sameness in climate, allowing technological advances to spread quickly. But what about in North and South America, with its long, north-south orientation and great variability in climate? How did people move and how quickly did societal innovations follow?

Genetic data carries the signature of ancient migrations

Using advanced genetic analysis techniques, evolutionary biologists at Brown University and Stanford University studied nearly 700 locations on human genomes drawn from more than five dozen populations. They say that technology spread more slowly in the Americas than in Eurasia and that the continents’ orientation seems to explain the difference. After humans arrived in the Americas 20,000 to 40,000 years ago, genetic data shows, the migrating populations didn’t interact as frequently as groups in Eurasia.

“If a lack of gene flow between populations is an indication of little cultural interaction,” the authors write in the American Journal of Physical Anthropology, “then a lower latitudinal rate of gene flow suggested for North American populations may partly explain the relatively slower diffusion of crops and technologies through the Americas when compared with the corresponding diffusion in Eurasia.”

“Our understanding of the peopling of the Americas will be refined by archaeological data and additional genetic samples,” added Sohini Ramachandran, assistant professor of biology in the Department of Ecology and Evolutionary Biology at Brown and the paper’s lead author. “But this is the signature of migration we see from genetic data.”

To tease out the migration patterns, Ramachandran and fellow researcher Noah Rosenberg from Stanford gathered genetic markers for 68 indigenous populations from 678 genetic markers in Eurasia and the Americas. The goal was to study the distribution of genetic variation among populations. The similarity or difference in genetic makeup among populations gave the scientists insights about migrations long ago.

To illustrate, when one population breaks off from its parent group, the individuals in the new population take their genomes and any distinct genetic mutations with them. From there, the new population may remain independent of the parent group because of distance or other factors, and over time its genetic makeup diverges from the parent. However, if the new population reunites regularly with its parent population — known as “back migration” — the genetic makeup of the two populations remains relatively close.

“When populations do not share migrants with each other very often,” Rosenberg explained, “their patterns of genetic variation diverge.”

Armed with the genetic background of cultures spanning the Americas and Eurasia, the researchers could test whether the east-west orientation of Eurasia supported a rapid spread of agriculture and other societal innovations, while the dissemination of those advances was slower in the Americas due to the north-south orientation. They found that to be the case: The populations in North and South America are, for the most part, more different from each other than the populations in Eurasia. The reason has to do with the differing climates that migrating peoples in the Americas found when they moved north to south.

“It’s harder to traverse those distances based on climate than it was in Eurasia,” Ramachandran said. “We find greater genetic differences (in the Americas’ populations) because of the difficulty in migration and the increased challenge of reuniting with neighboring populations.”

“Our result that genetic differentiation increases more with latitudinal distance between Native American populations than with longitudinal distance between Eurasian populations supports the hypothesis of a primary influence for continental axes of orientation on the diffusion of technology in Eurasia and the Americas,” the authors write.

The ancient turquoise mines of South Sinai

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Complete article with pictures

"His majesty of this God has sent the God's treasurer, the assistant and leader of the troupe, Her-Wer-Re, to the mining lands and he said: there is abundant turquoise in the hill."

With these words, Chief Her-Wer-Re began documenting the work of his mining expedition sent by the pharaoh (his majesty of this God) to Serabit al-Khadem in South Sinai during the Middle Kingdom Period (ca. 2055-1985 BC). In the inscriptions on his stele at the mine, he boasts of the success of his expedition despite rumors that turquoise ore might be lacking at that particular time of year: "My expedition returned complete in its entirety … I broke off in the first month of summer, bringing my precious stone … I accomplished my work with great success without a voice being raised against my work, which I have done excellently."

Rock inscriptions left by ancient Egyptian miners in South Sinai are rich with details of working conditions and weather, as well as praise for the pharaoh and the gods. They present a lively narrative of daily life that can be easily compared to modern business reports, or even a diary.

Sinai is often referred to in Arabic as “Ard Al-Fayrouz” (the land of turquoise) after its ancient Egyptian name "Ta Mefkat" or “Khetyou Mefkat”, which means turquoise terraces. Minerals were of great use in ancient times - for making royal jewelry and divine offerings, and more importantly for mummy ornaments and amulets, encouraging pharaohs since the Early Dynastic Period (ca. 3050-2890 BC) to send mining expeditions to extract turquoise and copper from South Sinai.

Wadi Maghara, Wadi Kharig, Bir Nasb and Serabit al-Khadem were among the premium mining spots in antiquity, and visiting them today offers a different experience for history and archaeology aficionados than the temples and tombs of the Nile Valley and Delta, which reflect ancient Egyptians’ beliefs in the afterlife. The archaeological sites of Southern Sinai relay aspects of daily life in old mining communities.

Such communities documented their work and adventures in the desert through rock inscriptions, graffiti (spontaneous wall drawings done by traveling expeditions), and occasionally chapels erected for the local God Hathor - also known as the Lady of Turquoise - once miners settled in.

The chief of the expedition would oversee documentation efforts: wall carvings at the mine’s entrance state the date of the expedition, the name of the chief and the group’s achievements. At Serabit al-Khadem, inscription number 56 reads: "Gallery (mine) has been opened by Chief Sanofret and named ‘Admiring the Beauty of Hathor.’” Other inscriptions at mining sites emphasize the power of the pharaoh over regions distant from the ruling capital in the Nile Valley. In Wadi Maghara, the wall carvings executed by miners show a typical Early Dynastic scene of the pharaoh smiting a man with a mace head.

Because ancient Egyptians tended to link all their life activities to religion, the miners were also keen on offering chapels and stelae (stone slabs or columns bearing commemorative inscriptions) to the local gods.

The site of Serabit al-Khadem still preserves the remains of the largest ancient Egyptian temple in the Sinai Peninsula. Located on an elevation, almost 800 meters above sea level, the temple is built of dozens of stelae inscribed by the chiefs of ancient expeditions from both the Middle and New King...

Ancient harbor at Yavneh-Yam was used for hostage exchange

An aerial view of the promonotory on which Yavneh-Yam is located. Photo: Skyview.

Archaeologists have long known that Yavneh-Yam, an archaeological site between the Israeli cities of Tel Aviv and Ashdod on the Mediterranean coast, was a functioning harbor from the second millennium B.C. until the Middle Ages. Now Tel Aviv University researchers have uncovered evidence to suggest that the site was one of the final strongholds of Early Islamic power in the region.

According to Prof. Moshe Fischer of TAU's Department of Archaeology and Near Eastern Cultures and head of the Yavneh-Yam dig, the recent discovery of a bath house from the Early Islamic period which made use of Roman techniques such as heated floors and walls, indicates that Arabic rulers maintained control of the site up until the end of the Early Islamic period in the 12th century AD. Considered alongside other datable artefacts — such as pottery, oil lamps and rare glass weights — this architectural feature demonstrates that Arabic control was maintained in Yavneh-Yam at a time when 70 percent of the surrounding land was in the hands of Christian crusaders.

The fortress was inhabited by military officers but not by high powered rulers, explains Prof. Fischer. Written Arabic sources from the same period, identifying Yavneh-Yam as a harbour, suggest that those who inhabited the fortress were responsible for hostage negotiations between the Arabic powers and the Christian crusaders, and the harbor itself served as a port for hostages to be transferred to their captors or returned home.


An aerial view of the excavated areas at Yavneh-Yam. Photo: Skyview.


Roman bath technology, Arabic adaptation and style

Working with Ph.D. candidate Itamar Taxel, Director of Excavations, Prof. Fischer has been excavating the site of Yavneh-Yam for the past twenty years. Among the earliest finds were two glass weights, dating from the 12th century and which bore the name of the then-ruling Arabic power, the Fatimid dynasty. The weights themselves were of interest and certainly indicated an Arabic presence at the site, the excavators say. But the extent of this presence has been illuminated by the discovery of a bath dating to this period and built according to Roman principles.

This year for the first time, researchers completed an in-depth analysis of the site's promontory, the piece of land protruding into the sea that made the site a natural harbor. The main structures, a series of fortification systems including a tower and strong walls that encircle the upper part of the hill, were discovered to be built in the distinctly Early Islamic style. The Roman baths uncovered within the fortress, says Prof. Fischer, leave little doubt that in the 12th century, the fortress was still inhabited by Arabs rather than Christian crusaders.

"This is an outstanding and rare find," he says, describing the baths as a scaled-down version of traditional Roman baths, heated by hot air circulating between double floors and pipes along the walls. The crusaders did not build these types of baths, and after the end of the Early Islamic period, they disappear altogether. "You don't see these installations again until the revival of such techniques by modern technology during the 19th century," explains Prof. Fischer. "This marked the finale of the use of a traditional Roman bath house in 12th century architecture."

Most likely, the fortress played host to a changing roster of military captains and their men, installing the baths to provide these men with additional creature comforts. Although the baths themselves are largely destroyed now, researchers found large marble slabs that adorned the walls, and ascertained that the view from the baths overlooked the sea.

A place of business?

The fortress served as more than a strategic look-out point to protect fragile Arab strongholds against the invasion of crusaders. Sources indicate that Yavneh-Yam, like the ports of Ashdod and Yaffa, was a place where Christian crusaders and Arabs haggled over hostages.

During this period, both the crusaders and Arabs took prisoners from the other side, who would later be exchanged, either for ransom or other prisoners-of-war who had been captured. The crusaders would have come over in boats to negotiate with Arab officials, then send word to the Ramla, the Arabic capital, waiting for orders and to conduct the required transaction.

Researchers will continue to excavate the site, now a national park, says Prof. Fischer. By connecting these new archaeological findings with historical evidence, "We get a nice picture of the complex relationship that existed in the Holy Land between a handful of Muslim enclaves, connected with the Arab rule in Cairo, surrounded by crusaders."

Fossil discovery could be our oldest human ancestor

Researchers have confirmed the age of possibly our oldest direct human ancestor at 1.98 million years old.

The discovery was made after researchers conducted further dating of the early human fossils, Australopithecus sediba, found in South Africa last year.

A series of studies carried out on newly exposed cave sediments at the Malapa Cave site in South Africa, where the fossils were found, has assisted researchers to determine their more precise age at 1.98 million years old, making the Malapa site one of the best dated early human sites in the world.

A series of papers published today in a special issue of the prestigious international journal Science provide a new, more precise age for the fossils, as well as more detailed studies of the hands, feet, pelvis and brain.

Uranium lead dating of the flowstone, conducted by the University of Melbourne combined with palaeomagnetic analysis sediments surrounding the fossils, conducted by La Trobe University provide the tightly constrained new age.

The team was able to pin down the age of the fossils to within 3000 years of 1.98 million years, a massive advance on the age range of around 200,000 years from the 2010 estimate.

Dr Robyn Pickering of the University of Melbourne's School of Earth Sciences, a lead researcher involved in the dating of the flowstone surrounding the fossils said researchers had long been searching for fossils from this time period to answer questions about the beginnings of our own genus Homo.

"Knowing the age of the fossils is critical to placing them in our family tree, and this new age means that Australopithecus sediba is the current best candidate for our most distant human ancestor."

"The results of these studies present arguably the most precise dates ever achieved for any early human fossils," she said.

It appears the fossils were deposited in the Malapa Cave during a 3,000-year period around 1.98 million years when the Earth's magnetic field reversed itself by 180 degrees and back again.

Dr Andy Herries from the Archaeology Program at La Trobe University who undertook the palaeomagnetic analysis said our ability to date and correctly identify these rare magnetic reversal events was crucial.

"They enable us to better date fossil and archaeological sites in the future, as well as to understand the possible effects they have on climate, plants and animals," he said.

Professor Paul Dirks from James Cook University and Professor Lee Berger of the University of the Witwatersrand in Johannesburg led the team that originally discovered the fossils in 2008.

"It is through the new exposures and our understanding of the stratigraphy of the site, together with the advances we've made in the dating techniques that we can be even more precise now," Professor Dirk said.

"The strong collaboration between South African and Australian universities has allowed us to push the boundaries of what was once thought possible in dating critical moments in early human origins in Africa," said Professor Berger.

More on Caiphas Family Ossuary

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“Miriam, Daughter of Yeshua, Son of Caiaphas”

A detailed examination of the alternative translations and authenticity can be found here: Dr Robert Cargill’s blog, KV8R

The ossuary includes the Aramaic inscription, which appears to read:

מרים ברת ישוע בר קיפא כהני מעזיה דבית עמרי

which translates:

“Miriam, Daughter of Yeshua, Son of Caiaphas,

Priests of Ma’aziah from Beth ‘Imri”

or

מרים ברת ישוע בר קיפא כהן דמעזיה דבית עמרי

which translates:

“Miriam, Daughter of Yeshua, Son of Caiaphas,
Priest of Ma’aziah from Beth ‘Imri”

or, as Jack Kilmon suggests

“Miriam, Daughter of Yeshua Bar Qayafa,
Priest of (the course of) Ma’aziah of the House of ‘Omri”

Anatomically modern humans interbred with more archaic hominin forms even before they migrated out of Africa

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It is now widely accepted that the species Homo sapiens originated in Africa and eventually spread throughout the world. But did those early humans interbreed with more ancestral forms of the genus Homo, for example Homo erectus, the "upright walking man," Homo habilis, – the "tool-using man" or Homo neanderthalensis, the first artists of cave-painting fame?

Direct studies of ancient DNA from Neanderthal bones suggest interbreeding did occur after anatomically modern humans had migrated from their evolutionary cradle in Africa to the cooler climates of Eurasia, but what had happened in Africa remained a mystery – until now.

In a paper published in the Proceedings of the National Academy of Sciences, or PNAS, a team led by Michael Hammer, an associate professor and research scientist with the UA's Arizona Research Labs, provides evidence that anatomically modern humans were not so unique that they remained separate.

"We found evidence for hybridization between modern humans and archaic forms in Africa. It looks like our lineage has always exchanged genes with their more morphologically diverged neighbors," said Hammer, who also holds appointments in the UA's department ofecology and evolutionary biology, the school of anthropology, the BIO5 Institute and the Arizona Cancer Center.

Hammer added that recent advances in molecular biology have made it possible to extract DNA from fossils tens of thousands of years old and compare it to that of modern counterparts.

However, "We don't have fossil DNA from Africa to compare with ours," he said. "Neanderthals lived in colder climates, but the climate in more tropical areas make it very tough for DNA to survive that long, so recovering usable samples from fossil specimens is extremely difficult if not impossible."

"Our work is different from the research that led to the breakthroughs in Neanderthal genetics," he explained. "We couldn't look directly for ancient DNA that is 40,000 years old and make a direct comparison."

To get past this hindrance, Hammer's team followed a computational and statistical approach.

"Instead, we looked at DNA from modern humans belonging to African populations and searched for unusual regions in the genome."

Because nobody knows the DNA sequences of those now extinct archaic forms, Hammer's team first had to figure out what features of modern DNA might represent fragments that were brought in from archaic forms.

"What we do know is that the sequences of those forms, even the Neanderthals, are not that different from modern humans," he said. "They have certain characteristics that make them different from modern DNA."

The researchers used simulations to predict what ancient DNA sequences would look like had they survived within the DNA of our own cells.

"You could say we simulated interbreeding and exchange of genetic material in silico," Hammer said. "We can simulate a model of hybridization between anatomically modern humans and some archaic form. In that sense, we simulate history so that we can see what we would expect the pattern to look like if it did occur."

According to Hammer, the first signs of anatomically modern features appeared about 200,000 years ago.

First, the team sequenced vast regions of human genomes from samples taken from six different populations living in Africa today and tried to match up their sequences with what they expected those sequences to look like in archaic forms. The researchers focused on non-coding regions of the genome, stretches of DNA that do not contain genes, which serve as the blueprints for proteins.

"Then we asked ourselves what does the general pattern of variation look like in the DNA that we sequenced in those African populations, and we started to look at regions that looked unusual," Hammer said. "We discovered three different genetic regions fit the criteria for being archaic DNA still present in the genomes of sub-Saharan Africans. Interestingly, this signature was strongest in populations from central Africa."

The scientists applied several criteria to tag a DNA sequence as archaic. For example, if a DNA sequence differed radically from the ones found in a modern population, it was likely to be ancient in origin. Another telltale sign is how far it extends along a chromosome. If an unusual piece is found to stretch a long portion of a chromosome, it is an indication of being brought into the population relatively recently.

"We are talking about something that happened between 20,000 and 60,000 years ago – not that long ago in the scheme of things," Hammer said. "If interbreeding occurs, it's going to bring in a whole chromosome, and over time, recombination events will chop the chromosome down to smaller pieces. And those pieces will now be found as short, unusual fragments. By looking at how long they are we can get an estimate of how far back the interbreeding event happened."

Hammer said that even though the archaic DNA sequences account for only two or three percent of what is found in modern humans, that doesn't mean the interbreeding wasn't more extensive.

"It could be that this represents what's left of a more extensive archaic genetic content today. Many of the sequences we looked for would be expected to be lost over time. Unless they provide a distinct evolutionary advantage, there is nothing keeping them in the population and they drift out."

In a next step, Hammer's team wants to look for ancient DNA regions that conferred some selective advantage to the anatomically modern humans once they acquired them.

"We think there were probably thousands of interbreeding events," Hammer said. "It happened relatively extensively and regularly."

"Anatomically modern humans were not so unique that they remained separate," he added. "They have always exchanged genes with their more morphologically diverged neighbors. This is quite common in nature, and it turns out we're not so unusual after all."

Humans Shaped Stone Axes 1.8 Million Years Ago

A new study suggests that Homo erectus, a precursor to modern humans, was using advanced toolmaking methods in East Africa 1.8 million years ago, at least 300,000 years earlier than previously thought. The study, recently published in Nature, raises new questions about where these tall and slender early humans originated and how they developed sophisticated tool-making technology.


Early humans were using stone hand axes as far back as 1.8 million years ago. (Credit: Pierre-Jean Texier, National Center of Scientific Research, France)

Homo erectus appeared about 2 million years ago, and ranged across Asia and Africa before hitting a possible evolutionary dead-end, about 70,000 years ago. Some researchers think Homo erectus evolved in East Africa, where many of the oldest fossils have been found, but the discovery in the 1990s of equally old Homo erectus fossils in the country of Georgia has led others to suggest an Asian origin. The study in Nature does not resolve the debate but adds new complexity. At 1.8 million years ago, Homo erectus in Dmanisi, Georgia was still using simple chopping tools while in West Turkana, Kenya, according to the study, the population had developed hand axes, picks and other innovative tools that anthropologists call "Acheulian."

"The Acheulian tools represent a great technological leap," said study co-author Dennis Kent, a geologist with joint appointments at Rutgers University and Columbia University's Lamont-Doherty Earth Observatory. "Why didn't Homo erectus take these tools with them to Asia?"

In the summer of 2007, a team of French and American researchers traveled to Kenya's Lake Turkana in Africa's Great Rift Valley, where earth's plates are tearing apart and some of the earliest humans first appear. Anthropologist Richard Leakey's famous find--Turkana Boy, a Homo erectus teenager who lived about 1.5 million years ago -- was excavated on Lake Turkana's western shore and is still the most complete early human skeleton found so far.

Six miles from Turkana Boy, the researchers headed for Kokiselei, an archeological site where both Acheulian and simpler "Oldowan" tools had been found earlier. Their goal: to establish the age of the tools by dating the surrounding sediments. Past flooding in the area had left behind layers of silt and clay that hardened into mudstone, preserving the direction of Earth's magnetic field at the time in the stone's magnetite grains. The researchers chiseled away chunks of the mudstone at Kokiselei to later analyze the periodic polarity reversals and come up with ages. At Lamont-Doherty's Paleomagnetics Lab, they compared the magnetic intervals with other stratigraphic records to date the archeological site to 1.76 million years.

"We suspected that Kokiselei was a rather old site, but I was taken aback when I realized that the geological data indicated it was the oldest Acheulian site in the world," said the study's lead author, Christopher Lepre, a geologist who also has joint appointments at Rutgers and Lamont-Doherty. The oldest Acheulian tools previously identified appear in Konso, Ethiopia, about 1.4 million years ago, and India, between 1.5 million and 1 million years ago.

The Acheulian tools at Kokiselei were found just above a sediment layer associated with a polarity interval called the "Olduvai Subchron." It is named after Tanzania's Olduvai Gorge, where pioneering work in the 1930s by Leakey's parents, Louis and Mary, uncovered a goldmine of early human fossils. In a study in Earth and Planetary Science Letters last year, Lepre and Kent found that a well-preserved Homo erectus skull found on east side of Lake Turkana, at Koobi Fora Ridge, also sat above the Olduvai Subchron interval, making the skull and Acheulian tools in West Turkana about the same age.

Anthropologists have yet to find an Acheulian hand axe gripped in a Homo erectus fist but most credit Homo erectus with developing the technology. Acheulian tools were larger and heavier than the pebble-choppers used previously and also had chiseled edges that would have helped Homo erectus butcher elephants and other scavenged game left behind by larger predators or even have allowed the early humans to hunt such prey themselves. "You could whack away at a joint and dislodge the shoulder from the arm, leg or hip," said Eric Delson, a paleoanthropologist at CUNY's Lehman College who was not involved in the study. "The tools allowed you to cut open and dismember an animal to eat it."

The skill involved in manufacturing such a tool suggests that Homo erectus was dexterous and able to think ahead. At Kokiselei, the presence of both tool-making methods -- Oldowan and Acheulian-- could mean that Homo erectus and its more primitive cousin Homo habilis lived at the same time, with Homo erectus carrying the Acheulian technology to the Mediterranean region about a million years ago, the study authors hypothesize. Delson wonders if Homo erectus may have migrated to Dmanisi, Georgia, but "lost" the Acheulian technology on the way.

The East African landscape that Homo erectus walked from about 2 million to 1.5 million years ago was becoming progressively drier, with savanna grasslands spreading in response to changes in the monsoon rains. "We need to understand also the ancient environment because this gives us an insight into how processes of evolution work -- how shifts in early human biology and behavior are potentially caused by changes in the climate, vegetation or animal life that is particular to a habitat," said Lepre. The team is currently excavating a more than 2 million year old site in Kenya to learn more about the early Oldowan period.