10 Haziran 2019 Pazartesi

Trophies made from human skulls hint at regional conflicts around the time of Maya civilization's mysterious collapse


Gabriel D. Wrobel, Michigan State University


Two trophy skulls, recently discovered by archaeologists in the jungles of Belize, may help shed light on the little-understood collapse of the once powerful Classic Maya civilization.
The defleshed and painted human skulls, meant to be worn around the neck as pendants, were buried with a warrior over a thousand years ago at Pacbitun, a Maya city. They likely represent gruesome symbols of military might: war trophies made from the heads of defeated foes.



Fragment of the Pacbitun trophy skull. Drawings by Christophe Helmke; Laserscan model by Jesse Pruitt, CC BY-ND


Both skulls are similar to depictions of trophy skulls worn by victorious soldiers in stone carvings and on painted ceramic vessels from other Maya sites.



A carving from the Maya city of Yaxchilan depicts the local ruler forcing a subdued captive to kiss the shield of his captor. At the small of his back, the victorious king wears a decorated trophy skull. Drawing by Ian Graham, CC BY-ND


Drilled holes likely held feathers, leather straps or both. Other holes served to anchor the jaws in place and suspend the cranium around the warrior’s neck, while the backs were sawed off to make the skulls lie flat on the wearer’s chest.
Flecks of red paint decorate one of the jaws. It’s carved with glyphic writing that includes what my collaborator Christophe Helmke, an expert on Maya writing, believes is the first known instance of the Maya term for “trophy skull.”
What do these skulls — where they were found and who they were from — tell us about the end of a powerful political system that thrived for centuries, covering southeastern Mexico, all of Guatemala and Belize, and portions of Honduras and El Salvador? My colleagues and I are thinking about them as clues to understanding this tumultuous period.


What ended a civilization?

The vast Maya empire flourished throughout Central America, with the first major cities appearing between 750 and 500 B.C. But beginning in the southern lowlands of Guatemala, Belize and Honduras in the eighth century A.D., people abandoned major Maya cities throughout the region. Archaeologists are fascinated by the mystery of what we call “the collapse” of this once powerful empire.
Earlier studies focused on identifying a single cause of the collapse. Could it have been environmental degradation resulting from the increasing demands of overpopulated cities? Warfare? Loss of faith in leaders? Drought?
All of these certainly took place, but none on its own fully explains what researchers know about the collapse that gradually swept through the landscape over the course of a century and a half. Today, archaeologists acknowledge the complexity of what happened.
Clearly violence and warfare contributed to the end of some southern lowland cities, as evidenced by quickly constructed fortifications identified by aerial LiDAR surveys at a number of sites.
Trophy skulls, together with a growing list of scattered finds from other sites in Belize, Honduras and Mexico, provide intriguing evidence that the conflict may have been civil in nature, pitting rising powers in the north against the established dynasties in the south.

Piecing together the skulls’ social context

Ceramic vessels found alongside the Pacbitun warrior and his (or her – the bones were too fragmentary to confidently determine sex) trophy skull date to the eighth or ninth century, just prior to the site’s abandonment.
During this period, Pacbitun and other Maya cities in the southern lowlands were beginning their decline, while Maya political centers in the north, in what is now the Yucatan of Mexico, rose to dominance. But the exact timing and nature of this power transition remains uncertain.
In many of these northern cities, art from this period is notoriously militaristic, abounding with skulls and bones and often showing war captives being killed and decapitated.



Portions of the Pakal Na trophy skull, found in the south with a northern warrior. Patricia A. McAnany, CC BY-ND


At Pakal Na, another southern site in Belize, a similar trophy skull was discovered inscribed with fire and animal imagery resembling northern military symbolism, suggesting a northern origin of the warrior it was buried with. The presence of northern military paraphernalia in the form of these skulls may point to a loss of control by local leaders.
Archaeologist Patricia McAnany has argued that the presence of northerners in the river valleys of central Belize may be related to the lucrative trade of cacao, the plant from which chocolate is made. Cacao was an important ingredient in rituals, and a symbol of wealth and power of Maya elites. However, the geology of the northern Yucatan makes it difficult to grow cacao on a large scale, necessitating the establishment of a reliable supply source from elsewhere.
At the northern site of Xuenkal, Mexico, Vera Tiesler and colleagues used strontium isotopes to pinpoint the geographic origin of a warrior and his trophy skull. He was local from the north. But the trophy skull he brought home, found atop his chest in burial, was from an individual who grew up in the south.
Other evidence at a number of sites in the southern highlands seems to mark a sudden and violent end for the community’s ruling order. Archaeologists have found evidence for the execution of one ruling family and desecration of sacred sites and elite tombs. At the regional capital site of Tipan Chen Uitz, approximately 20 miles (30 kilometers) east of Pacbitun, my colleagues and I found remains of several carved stone monuments that seem to have been intentionally smashed and strewn across the front of the main ceremonial pyramid.



Another portion of the Pacbitun trophy skull. Drawing by Shawn Morton, CC BY-ND


Trophy skulls and power dynamics

Archaeologists are not only interested in identifying the timing and the social and environmental factors associated with collapse, which vary in different regions. We’re also trying to figure out how specific communities and their leaders responded to the unique combinations of these stresses they faced.
While the evidence from just a handful of trophy skulls does not conclusively show that sites in parts of the southern lowlands were being overrun by northern warriors, it does at least point to the role of violence and, potentially, warfare as contributing to the end of the established political order in central Belize.
These grisly artifacts lend an intriguing element to the sweep of events that resulted in the end of one of the richest, most sophisticated, scientifically advanced cultures of its time.The Conversation

Gabriel D. Wrobel, Associate Professor of Anthropology, Michigan State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.

1 Haziran 2019 Cumartesi

Robots guarded Buddha's relics in a legend of ancient India



Two small figures guard the table holding the Buddha’s relics. Are they spearmen, or robots? British Museum, CC BY-NC-SA

Adrienne Mayor, Stanford University
As early as Homer, more than 2,500 years ago, Greek mythology explored the idea of automatons and self-moving devices. By the third century B.C., engineers in Hellenistic Alexandria, in Egypt, were building real mechanical robots and machines. And such science fictions and historical technologies were not unique to Greco-Roman culture.
In my recent book “Gods and Robots,” I explain that many ancient societies imagined and constructed automatons. Chinese chronicles tell of emperors fooled by realistic androids and describe artificial servants crafted in the second century by the female inventor Huang Yueying. Techno-marvels, such as flying war chariots and animated beings, also appear in Hindu epics. One of the most intriguing stories from India tells how robots once guarded Buddha’s relics. As fanciful as it might sound to modern ears, this tale has a strong basis in links between ancient Greece and ancient India.
The story is set in the time of kings Ajatasatru and Asoka. Ajatasatru, who reigned from 492 to 460 B.C., was recognized for commissioning new military inventions, such as powerful catapults and a mechanized war chariot with whirling blades. When Buddha died, Ajatasatru was entrusted with defending his precious remains. The king hid them in an underground chamber near his capital, Pataliputta (now Patna) in northeastern India.

A sculpture depicting the distribution of the Buddha’s relics. Los Angeles County Museum of Art/Wikimedia Commons

Traditionally, statues of giant warriors stood on guard near treasures. But in the legend, Ajatasatru’s guards were extraordinary: They were robots. In India, automatons or mechanical beings that could move on their own were called “bhuta vahana yanta,” or “spirit movement machines” in Pali and Sanskrit. According to the story, it was foretold that Ajatasatru’s robots would remain on duty until a future king would distribute Buddha’s relics throughout the realm.

Ancient robots and automatons


A statue of Visvakarman, the engineer of the universe. Suraj Belbase/Wikimedia Commons, CC BY-SA


Hindu and Buddhist texts describe the automaton warriors whirling like the wind, slashing intruders with swords, recalling Ajatasatru’s war chariots with spinning blades. In some versions the robots are driven by a water wheel or made by Visvakarman, the Hindu engineer god. But the most striking version came by a tangled route to the “Lokapannatti” of Burma – Pali translations of older, lost Sanskrit texts, only known from Chinese translations, each drawing on earlier oral traditions.
In this tale, many “yantakara,” robot makers, lived in the Western land of the “Yavanas,” Greek-speakers, in “Roma-visaya,” the Indian name for the Greco-Roman culture of the Mediterranean world. The Yavanas’ secret technology of robots was closely guarded. The robots of Roma-visaya carried out trade and farming and captured and executed criminals.
Robot makers were forbidden to leave or reveal their secrets – if they did, robotic assassins pursued and killed them. Rumors of the fabulous robots reached India, inspiring a young artisan of Pataliputta, Ajatasatru’s capital, who wished to learn how to make automatons.
In the legend, the young man of Pataliputta finds himself reincarnated in the heart of Roma-visaya. He marries the daughter of the master robot maker and learns his craft. One day he steals plans for making robots, and hatches a plot to get them back to India.
Certain of being slain by killer robots before he could make the trip himself, he slits open his thigh, inserts the drawings under his skin and sews himself back up. Then he tells his son to make sure his body makes it back to Pataliputta, and starts the journey. He’s caught and killed, but his son recovers his body and brings it to Pataliputta.
Once back in India, the son retrieves the plans from his father’s body, and follows their instructions to build the automated soldiers for King Ajatasatru to protect Buddha’s relics in the underground chamber. Well hidden and expertly guarded, the relics – and robots – fell into obscurity.


The sprawling Maurya Empire in about 250 B.C. Avantiputra7/Wikimedia Commons, CC BY-SA


Two centuries after Ajatasatru, Asoka ruled the powerful Mauryan Empire in Pataliputta, 273-232 B.C. Asoka constructed many stupas to enshrine Buddha’s relics across his vast kingdom. According to the legend, Asoka had heard the legend of the hidden relics and searched until he discovered the underground chamber guarded by the fierce android warriors. Violent battles raged between Asoka and the robots.
In one version, the god Visvakarman helped Asoka to defeat them by shooting arrows into the bolts that held the spinning constructions together; in another tale, the old engineer’s son explained how to disable and control the robots. At any rate, Asoka ended up commanding the army of automatons himself.

Exchange between East and West

Is this legend simply fantasy? Or could the tale have coalesced around early cultural exchanges between East and West? The story clearly connects the mechanical beings defending Buddha’s relics to automatons of Roma-visaya, the Greek-influenced West. How ancient is the tale? Most scholars assume it arose in medieval Islamic and European times.
But I think the story could be much older. The historical setting points to technological exchange between Mauryan and Hellenistic cultures. Contact between India and Greece began in the fifth century B.C., a time when Ajatasatru’s engineers created novel war machines. Greco-Buddhist cultural exchange intensified after Alexander the Great’s campaigns in northern India.


Inscriptions in Greek and Aramaic on a monument originally erected by King Asoka at Kandahar, in what is today Afghanistan. World Imaging/Wikimedia Commons


In 300 B.C., two Greek ambassadors, Megasthenes and Deimachus, resided in Pataliputta, which boasted Greek-influenced art and architecture and was the home of the legendary artisan who obtained plans for robots in Roma-visaya. Grand pillars erected by Asoka are inscribed in ancient Greek and name Hellenistic kings, demonstrating Asoka’s relationship with the West. Historians know that Asoka corresponded with Hellenistic rulers, including Ptolemy II Philadelphus in Alexandria, whose spectacular procession in 279 B.C. famously displayed complex animated statues and automated devices.
Historians report that Asoka sent envoys to Alexandria, and Ptolemy II sent ambassadors to Asoka in Pataliputta. It was customary for diplomats to present splendid gifts to show off cultural achievements. Did they bring plans or miniature models of automatons and other mechanical devices?
I cannot hope to pinpoint the original date of the legend, but it is plausible that the idea of robots guarding Buddha’s relics melds both real and imagined engineering feats from the time of Ajatasatru and Asoka. This striking legend is proof that the concepts of building automatons were widespread in antiquity and reveals the universal and timeless link between imagination and science.



Adrienne Mayor is the author of:

Gods and Robots: Myths, Machines, and Ancient Dreams of TechnologyThe Conversation

Princeton University Press provides funding as a member of The Conversation US.

Adrienne Mayor, Research Scholar, Classics and History and Philosophy of Science, Stanford University
This article is republished from The Conversation under a Creative Commons license. Read the original article.

I'm an evolutionary biologist – here's why this ancient fungal fossil discovery is so revealing



Do fungi like this Penicillium mold, which produces the the antibiotic penicillin, trace their origins to an ancestor that lived a billion years ago? Rattiya Thongdumhyu/Shutterstock.com
Antonis Rokas, Vanderbilt University
Biologists don’t call them “the hidden kingdom” for nothing. With an estimated 5 million species, only a mere 100,000 fungi are known to scientists. This kingdom, which includes molds, yeasts, rusts and mushrooms, receives far less attention than plants or animals. This is particularly true for fossils of fungi, most of which are discovered while hunting for more charismatic, at least to the eyes of some, plant fossils.
Fungi were key partners of plants during their colonization of land approximately 500 million years ago – an important and well-documented evolutionary transition. Therefore, it is unsurprising that the earliest fungal fossils, found in 450 million-year-old rocks, resemble modern species associated with the roots of plants. But that conflicts with DNA-based estimates, which suggest that fungi originated much earlier – a billion or more years ago. It’s a riddle in the tree of life that evolutionary biologists like me have long been puzzled about.

Fossils versus DNA

For years scientists have tried to reconcile the fungal fossil record with estimates from analyses of fungal DNA. But some of their key morphological characters – that is, the shapes they take – can only be established via microscopic and chemical analyses. That includes the complex networks of microscopic thread-like filaments and cell walls made of chitin, which are also not visible to the naked eye. The effort seemed hopeless, until now.
Corentin Loron, a graduate student at the University of Liege in Belgium and colleagues, discovered microscopic, fossilized specimens of a fungus called Ourasphaira giraldae in shale rock from the Grassy Bay Formation in the Northwest Territories of Canada. Given that Ourasphaira is found on 1,000- to 900-million-year-old rocks, the new fossil pushes back the origin of fungi by half a billion years.

A very revealing fossil

But how did Loron deduce that these fossils are fungi? While most of us are quite familiar with the large reproductive structures of some fungi, such as mushrooms, most of us are less familiar with the fungal network of microscopic thread-like filaments that makes up their “bodies.”
Microscopical analyses of Ourasphaira show that it formed a network just like those made by modern fungi; and chemical analyses show that the cell walls of these microfossils contain chitin, again just like modern fungi.
The implications of this discovery are twofold.
First, the fossil singlehandedly reconciles DNA-based and paleontological estimates of fungal origins, pushing back the origin of Opisthokonta, a supergroup comprising fungi, animals and their single-celled relatives to at least a billion years ago. And second, the fossil gives us clues about the environments where the first fungi lived. Ourasphaira was found in a shale, a type of rock that forms at the muddy bottom of lakes and rivers. Since this particular shale appears to have been formed as a result of sedimentation from a shallow-water estuary, it may be the first fungi evolved where rivers met the seas a billion years ago.
It’s one more clue that helps fill in the picture on how life on earth evolved and one more step toward bringing this fascinating group of organisms to the limelight.The Conversation

Antonis Rokas, Cornelius Vanderbilt Chair in Biological Sciences and Professor of Biological Sciences and Biomedical Informatics, Vanderbilt University
This article is republished from The Conversation under a Creative Commons license. Read the original article.

Misreading the story of climate change and the Maya



Stucco frieze from Placeres, Campeche, Mexico, Early Classic period, c. 250-600 AD. Wolfgang Sauber/Wikimedia, CC BY-SA
Kenneth Seligson, California State University, Dominguez Hills
Carbon dioxide concentrations in Earth’s atmosphere have reached 415 parts per million – a level that last occurred more than three million years ago, long before the evolution of humans. This news adds to growing concern that climate change will likely wreak serious damage on our planet in the coming decades.
While Earth has not been this warm in human history, we can learn about coping with climate change by looking to the Classic Maya civilization that thrived between A.D. 250-950 in Eastern Mesoamerica, the region that is now Guatemala, Belize, Eastern Mexico, and parts of El Salvador and Honduras.
Many people believe that the ancient Maya civilization ended when it mysteriously “collapsed.” And it is true that the Maya faced many climate change challenges, including extreme droughts that ultimately contributed to the breakdown of their large Classic Period city-states.
However, the Maya did not disappear: Over 6 million Maya people live mainly in Eastern Mesoamerica today. What’s more, based on my own research in the Northern Yucatan Peninsula and work by my colleagues throughout the broader Maya region, I believe Maya communities’ ability to adapt their resource conservation practices played a crucial role in allowing them to survive for as long as they did. Instead of focusing on the final stages of Classic Maya civilization, society can learn from the practices that enabled it to survive for nearly 700 years as we consider the effects of climate change today.

The Classic Maya built more than 40 cities across Eastern Mesoamerica and made sophisticated advances in agriculture, mathematics and astronomy.


Adapting to dry conditions

The earliest villages in the Maya lowlands date as far back as 2000 B.C., with several large cities developing over the following 2,000 years. A combination of factors, including environmental changes, contributed to the breakdown of many of these large Preclassic centers after the start of the first millennium A.D.
Beginning around 250 A.D., populations once again began to grow steadily in the Maya lowlands. This was the Classic Period. Laser mapping has shown that by the eighth century A.D., sophisticated agricultural systems supported city-states of tens of thousands of people.
Available evidence suggests that although the climate remained relatively stable for much of the Classic Period, there were occasional periods of decreased precipitation. Additionally, each year was sharply divided between dry and rainy seasons. Maximizing water efficiency and storage, and timing the planting season correctly, were very important.

Plate with Maize God imagery, Mexico, 600-900 A.D. Wikimedia

If the rains did not come as expected for a year or two, communities could rely on stored water. However, longer droughts stressed their political hierarchy and complex inter-regional trade networks. The overarching key to survival was learning to adapt to changing environmental conditions.
For example, the Maya developed ever more elaborate terrace and irrigation networks to protect against soil runoff and nutrient depletion. They engineered intricate drainage and storage systems that maximized the capture of rainwater.
They carefully managed forests by monitoring the growth cycles of particularly useful trees. And they developed fuel-efficient technologies, such as burnt lime pit-kilns, to sustain environmental resources.

An experimental burnt lime pit-kiln, modeled on ancient pit-kilns excavated in the Northern Lowlands. Kenneth Seligson, CC BY-ND


Coping with megadroughts

Available data indicate that a series of particularly intense droughts, lasting anywhere from three to 20 years or more, hit the Maya lowlands in the ninth and 10th centuries A.D. Archaeologists are still debating the exact timing, intensity, impact and location of these droughts. For instance, it appears that not all areas of the Maya lowlands were affected equally. As of now, these “megadroughts” do appear to line up with the final centuries of the Classic Period.
One main consequence was that people moved around the lowlands. Dramatic population growth in certain areas suggests that local communities may have absorbed these migrant groups. There also is evidence that they adopted new resource conservation practices to mitigate the additional stress of supporting larger numbers of people.

Decline and breakdown

During the ninth and 10th centuries A.D., many of the larger Classic Maya city-states fell as a result of several interrelated long-term trends, including population growth, increasingly frequent warfare and an ever more complex bureaucracy. Declining rainfall made a risky situation worse.
In the end, several population centers did experience relatively rapid final abandonment events. However, different areas experienced breakdowns at various times over a period of more than two centuries. Calling this series of events a collapse overlooks Maya communities’ ability to persevere for generations against mounting challenges.

Pyramid at the site of Kiuic in Yucatan State, Mexico. Kenneth Seligson, CC BY-ND

We can see similar patterns in several other well-known civilizations. Ancestral Puebloan communities in the U.S. Southwest, formerly known as Anasazi, developed intricate irrigation networks to farm a naturally arid landscape starting around the beginning of the first millennium A.D. When rainfall began to decline in the 12th and 13th centuries A.D., they reorganized into smaller units and moved around the landscape. This strategy allowed them to survive longer than they would have by remaining in place.
Angkor, the capital of the ancient Khmer Empire located in modern Cambodia, developed very complex irrigation networks starting in the ninth century A.D. to manage annual floods. Increasingly irregular annual rain cycles over the course of the 13th and 14th centuries A.D. stressed the system’s flexibility. Difficulty in adapting to these changes was one factor that contributed to Angkor’s gradual decline.

All societies need to be flexible

Many observers have drawn parallels between disastrous climate shifts in the past and the fate of modern society. I believe this perspective is too simplistic. Current scientific understanding of climate change is not perfect, but modern societies clearly know a lot about what is happening and what needs to be done to avoid catastrophic warming.

Maya woman in Chichicastenango, Guatemala, photographed in 2014. Stefano Ravalli, CC BY-SA

However, they also require the will to tackle critical threats. The Classic Maya proactively addressed climate challenges by adapting their ecological practices to a changing environment. This helped many communities survive for centuries through waves of intense drought. Their experience, and the persistence of other ancient civilizations, shows the importance of knowledge, planning and structural flexibility.
There also is an important difference between natural climate stresses on ancient societies and the human-induced challenge we face today: Modern humans can have a far greater impact on the survival of future generations. The Maya could only react to climatic conditions, but we know how to address the causes of climate change. The challenge is choosing to do so.The Conversation

Kenneth Seligson, Assistant Professor of Anthropology, California State University, Dominguez Hills
This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ancient DNA is revealing the origins of livestock herding in Africa



Livestock, like these goats in the Rift Valley of Tanzania, are critical to household economies in East Africa. Katherine Grillo, CC BY-ND
Mary Prendergast, Saint Louis University – Madrid and Elizabeth Sawchuk, Stony Brook University (The State University of New York)
Visitors to East Africa are often amazed by massive herds of cattle with a gorgeous array of horn, hump and coat patterns. Pastoralism – a way of life centered around herding – is a central part of many Africans’ identity. It’s also a key economic strategy that is now threatened by climate change, rising demands for meat, urban sprawl and land conflicts.
Pastoralism’s roots could hold clues to help solve these modern challenges. Studies suggest that traditional ways of managing livestock – moving around and exchanging with other herders – enabled herders to cope with environmental instability and economic change over the past several thousand years. Research is also helping scientists understand how millennia of herding – and livestock dung – have shaped East Africa’s savannas and wildlife diversity.
So how did pastoralism get started in Africa? Currently most archaeologists think wild ancestors of today’s domestic cattle, sheep and goats were first domesticated in the “Fertile Crescent” of the Middle East. Archaeological research shows herding began to appear in and spread from what is now Egypt around 8,000 years ago. By 5,000 years ago, herders were burying their dead in elaborate monumental cemeteries near a lakeshore in Kenya. Two millennia later, pastoralist settlements were present across a wide part of East Africa and by at least 2,000 years ago, livestock appear in South Africa.


Large herds of cattle graze near Lake Manyara in Tanzania, where they’ve been a key part of the economy for 3,000 years. Mary Prendergast, CC BY-ND

Much remains unanswered: Did animals spread mostly through exchange, just like cash circulates widely while people mostly stay put? Were people moving long distances with their herds, traversing the continent generation by generation? Were there many separate migrations or few, and what happened when immigrant herders met indigenous foragers? We decided to ask these questions using ancient DNA from archaeological skeletons from across East Africa.

Piecing together the genetic history of herders

Archaeologists study ancient people’s trash – broken clay pots, abandoned jewelry, leftover meals, even feces – but we also study the people themselves. Bioarchaeologists examine human bones and teeth as indicators of health, lifestyle and identity.
Now it’s also possible to sequence ancient DNA to look at genetic ancestry. Until recently, though, Africa has been on the sidelines of the “ancient DNA revolution” for a variety of reasons. Advances in DNA sequencing have created new opportunities to study African population history.



In our new research, our team sequenced the genomes of 41 people buried at archaeological sites in Kenya and Tanzania, more than doubling the number of ancient individuals with genome-wide data from sub-Saharan Africa. We obtained radiocarbon dates from the bones of 35 of these people – important because direct dates on human remains are virtually nonexistent in East Africa. Working as a team meant forging partnerships among curators, archaeologists and geneticists, despite our different work cultures and specialized vocabularies.
The people we studied were buried with a wide variety of archaeological evidence linking them to foraging, pastoralism and, in one case, farming. These associations are not airtight – people may have shifted between foraging and herding – but we rely on cultural traditions, artifact types and food remains to try to understand how people were getting their meals.


Red dots are archaeological sites in the authors’ study. Gray dots mark selected Rift Valley sites. Prettejohn’s Gully geological survey, marked by a black star, produced the oldest ancient DNA in Kenya. Elizabeth Sawchuk, CC BY-ND

After we grouped individuals based on the lifestyles we inferred from associated archaeological evidence, we compared their ancient genomes to those of hundreds of living people, and a few dozen ancient people from across Africa and the adjacent Middle East. We were looking for patterns of genetic relatedness.
Some of our ancient samples did not resemble other known groups. Despite major efforts to document the vast genetic variation in Africa, there’s a long way to go. There are still gaps in modern data, and no ancient data at all for much of the continent. Although we can identify groups that share genetic similarities with the ancient herders, this picture no doubt will become clearer as more data become available.

Herding expanded in stages

So far we can tell that herding spread via a complex, multi-step process. The first step involved a “ghost population” – one for which we don’t have direct genetic evidence yet. These people drew about half of their ancestry from groups who lived in either the Middle East or presumably northeastern Africa (a region for which we have no relevant aDNA) or both, and about half from Sudanese groups. As this group spread southward – likely with livestock – they interacted and genetically integrated with foragers already living in East Africa. This period of interaction lasted from perhaps around 4,500-3,500 years ago.
After this occurred, it appears that ancient herders genetically kept to themselves. Methods that let us estimate the average date of admixture – that is, gene flow between previously isolated groups – indicate integration largely stopped by around 3,500 years ago. This suggests there were social barriers that kept herders and foragers from having children together, even if they interacted in plenty of other ways. Alternatively, there may have been far fewer foragers than herders, so that gene flow among these communities didn’t have a big demographic impact.
By around 1,200 years ago, we document new arrivals of people related to recent Sudanese and – for the first time – West African groups, associated with early iron-working and farming. After this point, a social mosaic made up of farmers, herders and foragers became typical of East Africa, and remains so today.
One interesting question is how early pastoralists used their herds. For instance, were they drinking milk? Although many East Africans today carry a genetic mutation that helps them digest milk into adulthood, this may be a recent development. We were able to test eight individuals for the genetic variant responsible for lactase persistence in many East African pastoralists today. Just one man, who lived in Tanzania 2,000 years ago, carried this variant. Maybe dairying was rare, but it’s also possible people found creative culinary solutions – for example, fermented milk or yogurt – to avoid indigestion.

Cultural and biological diversity are not the same

Archaeologists have a saying that “pots are not people.” Particular artifact styles are not assumed to reflect concrete identities – just as we wouldn’t assume today that the choice of kilts versus lederhosen is determined by DNA.


Pottery is the Tupperware of the past – durable and ubiquitous on archaeological sites. But there isn’t always a link between styles and ancestral identities. We compared burials associated with two distinctive artifact traditions – Savanna Pastoral Neolithic (A) and Elmenteitan (B) – and found no genetic differences. Steven Goldstein at the National Museum of Kenya, CC BY-NC-ND

In Kenya and Tanzania, archaeologists had previously identified two early herder cultural traditions distinguished by different pottery styles, stone tool sources, settlement patterns and burial practices. The people who created these cultures lived at roughly the same time and in the same area. Some scholars hypothesized that they spoke different languages and had different “ethnic” identities.
Our recent study found no evidence for genetic differentiation among people associated with these different cultures; in fact, we were struck by how closely related they were. Now archaeologists can ask a different question: Why did distinct cultures emerge among such closely related neighbors?


Ancient DNA is shedding new light on the history of key areas for early herding, like the East African Rift Valley. Mary Prendergast, CC BY-ND


(Re)discovering lost places and people

Some of our most exciting findings came from unexpected places. Museum shelves are full of potentially game-changing collections that have yet to be studied or published. In a back corner of one storeroom, we found a tray containing two fragmentary human skeletons uncovered during a Rift Valley geological expedition at Prettejohn’s Gully in the 1960s. There was little contextual information, but with encouragement from curators we sampled the remains to see if we could at least determine their age.
We were shocked to learn that these 4,000-year-old burials provided the oldest DNA from Kenya, and that the man and woman buried at that site may have been some of the earliest herders in East Africa. Thanks to them, we can show that the spread of herding in Kenya involved several separate movements of ancestrally distinct groups. We have much to learn from older collections, and archaeologists don’t always need to dig to make new discoveries.


Archives are a key part of ancient DNA research, which sometimes leads to rediscovery of long-forgotten archaeological collections. Elizabeth Sawchuk at the National Museum of Kenya, CC BY-NC-ND

Ancient DNA research doesn’t just answer questions about our shared past. It also raises new ones that must be answered by other fields. Our results don’t tell us what migration and admixture mean in social terms. What prompted people to move with livestock? What happened when people with radically different lifestyles met? What became of the foragers who were living across East Africa throughout the past, and whose descendants are few and far between today?
Ultimately, we hope that by studying pastoralism in the past – and demonstrating the resilience of this way of life – we can contribute in some way to understanding the challenges facing herders today.The Conversation

Mary Prendergast, Professor of Anthropology, Saint Louis University – Madrid and Elizabeth Sawchuk, Postdoctoral Fellow and Research Assistant Professor of Anthropology, Stony Brook University (The State University of New York)
This article is republished from The Conversation under a Creative Commons license. Read the original article.

Trophies made from human skulls hint at regional conflicts around the time of Maya civilization's mysterious collapse

Gabriel D. Wrobel , Michigan State University Two trophy skulls, recently discovered by archaeologists in the jungles of Belize , m...