DNA data offers scientific look at 500 years of extramarital sex in Western Europe

By: Thomas Schmitt Attorney on November 14, 2019 / comment : 0 Anthropology, Genetics, Society, Western Europe

These days it's easy to resolve questions about paternity with over-the-counter test kits. Now, researchers have put DNA evidence together with long-term genealogical data to explore similar questions of biological fatherhood on a broad scale among people living in parts of Western Europe over the last 500 years.

Credit: Getty Images

The findings reported in Current Biology yielded some surprises. While the number of so-called extra-pair paternity (EPP) events overall was (not surprisingly) fairly low, their frequency varied considerably among people depending on their circumstances. Specifically, evidence of EPP events turned up much more often in people of lower socioeconomic status who lived in densely populated cities in the 19th century.

"Of course, extra-pair paternity, especially due to adultery, is a popular topic in gossip, jokes, TV series, and literature," said Maarten Larmuseau of KU Leuven and Histories, Belgium. "But scientific knowledge on this phenomenon is still highly limited, especially regarding the past.

"Our research shows that the chance of having extra-pair paternity events in your family history really depends on the social circumstances of your ancestors. If they lived in cities and were of the lower socioeconomic classes, the chances that there were EPP events in your family history are much higher than if they were farmers."

Evolutionarily speaking, it's clear that remaining faithful to one's partner isn't always the most advantageous strategy. Males may benefit from straying by siring extra offspring; females may benefit by mating with superior males. But in human societies over time, how often has EPP really happened?

In the new study, Larmuseau's team took the first broad look at this question to find that social context really matters. Their study covered a time period of several centuries during which there were dramatic changes in the human social environment, including the rapid urbanization that accompanied the Industrial Revolution in 19th century Western Europe. To estimate historical EPP rates among married couples, they identified 513 pairs of contemporary adult males living in Belgium and the Netherlands who, based on genealogical evidence, shared a common paternal ancestor and therefore--barring an EPP event--should have carried the same Y chromosome.

The evidence showed no significant difference in EPP rates between countries despite key religious differences, they report. But they varied widely with socioeconomic status and population density. The EPP rate was much lower among farmers and more well-to-do craftsmen and merchants (about 1%) than among lower class laborers and weavers (about 4%).

EPP rates also rose with population density. Putting the two together, the researchers report that the estimated EPP rates for the families varied by more than one order of magnitude, from about 0.5% among the middle to high classes and farmers living in the most sparsely populated towns to almost 6% for the low socioeconomic classes living in the most densely populated cities.

The researchers say the findings support evolutionary theories suggesting that individual incentives and opportunities for seeking or preventing extra-pair mating should depend on the social context. They also debunk the notion that EPP rates in Western society are generally high, they say, noting that the evidence puts average rates at around 1%.

Larmuseau says an interdisciplinary perspective will be important to understanding why certain factors like population density and socio-economic status have had such a strong influence on the EPP rate. "This is highly relevant because the causes of historical EPP events are hidden and diverse," he said.

Source: Cell Press [November 14, 2019]

Complex society discovered in birds

By: Thomas Schmitt Attorney on November 04, 2019 / comment : 0 Biology, Evolution, Society, Wildlife

Multilevel societies have, until now, only been known to exist among large-brained mammals including humans, other primates, elephants, giraffes, and dolphins. Now, scientists from the Max Planck Institute of Animal Behavior and the University of Konstanz report the existence of a multilevel society in a small-brained bird, the vulturine guineafowl (Acryllium vulturinum). The study, published in Current Biology, suggests that the birds can keep track of social associations with hundreds of other individuals--challenging the notion that large brains are a requirement for complex societies and providing a clue as to how these societies evolved.

Vulturine guineafowl move in highly cohesive groups. This cohesion allows them to coordinate their actions as they move together through the landscape, and therefore maintain stable group membership  over extensive periods of time [Credit: James Klarevas]

Multilevel societies occur when social units, such as pairs, of animals form groups that have stable membership, and these groups then associate preferentially with specific other groups. Because this requires the animals to keep track of individuals in both their own and other groups, the assumption has long been that multilevel societies should only exist in species with the intelligence to cope with this complexity. While many bird species live in groups, these are either open, lacking long-term stability, or highly territorial, lacking associations with other groups.

Vulturine guineafowl, however, present a striking exception: the researchers observed these birds, that are from an ancient lineage resembling dinosaurs more than birds, behaving highly cohesively without exhibiting the signature intergroup aggression that is common in other group-living birds. And they can manage this despite having a relatively small brain, even relative to other birds. "They seemed to have the right elements to form complex social structures, and yet nothing was known about them," says Danai Papageorgiou, lead author on the paper and a PhD student at the Max Planck Institute of Animal Behavior.

The study, which is the first ever conducted on the species, involved tracking social relationships over the course of multiple seasons in a population of over 400 adult birds in a field site in Kenya. The researchers individually marked all birds in the population, and by observing them they discovered that the population comprised 18 distinct social groups (with 13 to 65 individuals in each). What struck the researchers is that these groups remained stable, despite regularly overlapping with one or more other groups both during the day and at night-time roosts.

Groups of vulturine guineafowl can become very large, and when multiple groups come into contact the number of birds moving together can reach into the hundreds. However, when these 'super-groups' eventually split, they do so back  into their original stable group units, meaning that individuals are knowledgeable about who is part  of their group and who is not [Credit: Danai Papageorgiou]

To see if these groups preferentially associated with one another, the researchers attached GPS tags to a sample of individuals in each group. This meant that the position of every single group was recorded continuously each day, which allowed researchers to simultaneously observe how all 18 groups in the population were interacting. The researchers found that groups associated with each other based on preference, rather than random encounters, and also showed that intergroup associations were more likely to take place during specific seasons and around particular physical features in the landscape.

"To our knowledge, this is the first time a social structure like this has been described for birds," says Papageorgiou. "It is remarkable to observe hundreds of birds coming out of a roost and splitting up perfectly into completely stable groups every single day. How do they do that? It's obviously not just about being smart."

Despite being understudied, guineafowl have challenged our understanding of how sociality has evolved. "This discovery raises a lot of questions about the mechanisms underlying complex societies and has opened up exciting possibilities of exploring what is it about this bird that has made them evolve a social system that is in many ways more comparable to a primate than to other birds," says Damien Farine, senior author on the paper and a Principal Investigator at the Max Planck Institute of Animal Behavior and the Centre for the Advanced Study of Collective Behaviour at the University of Konstanz.

But, vulturine guineafowl hold some important clues about how complex societies might have evolved. "Many examples of multilevel societies -- primates, elephants and giraffes -- might have evolved under similar ecological conditions as vulturine guineafowl," says Farine.

Source: Max Planck Society [November 04, 2019]

Private property, not productivity, precipitated Neolithic agricultural revolution

By: Thomas Schmitt Attorney on October 11, 2019 / comment : 0 Archaeology, Iran, Iraq, Middle East, Society

Humankind first started farming in Mesopotamia about 11,500 years ago. Subsequently, the practices of cultivating crops and raising livestock emerged independently at perhaps a dozen other places around the world, in what archaeologists call the Neolithic Agricultural Revolution. It's one of the most thoroughly-studied episodes in prehistory - but a new paper in the Journal of Political Economy shows that most explanations for it don't agree with the evidence, and offers a new interpretation.

Cave painting of cow & horses, Lascaux, France [Credit: Alamy]

With farming came a vast expansion of the realm over which private property governed access to valued goods, replacing the forager social norms around sharing food upon acquisition. A common explanation is that farming increased labor productivity, which then encouraged the adoption of private property by providing incentives for the long-term investments required in a farming economy.

"But it's not what the data are telling us", says Santa Fe Institute economist Samuel Bowles, a co-author of the paper. "It is very unlikely that the number of calories acquired from a day's work at the advent of farming made it a better option than hunting and gathering and it could well have been quite a bit worse."

Prior studies, including those of human and animal bones, suggest that farming actually took an extreme nutritional toll on early adopters and their livestock. So why farm in the first place?

Some have suggested an inferior technology could have been imposed by political elites as a strategy for extracting taxes, tribute, or rents. But farming was independently adopted millennia before the emergence of governments or political elites capable of imposing a new way of life on heavily-armed foraging communities.

Bowles and co-author Jung-Kyoo Choi, an economist at Kyungpook National University in South Korea, use both evolutionary game theory and archaeological evidence to propose a new interpretation of the Neolithic. Based on their model, a system of mutually recognized private property rights was both a precondition for farming and also a means of limiting costly conflicts among members of a population.

While rare among foragers, private property did exist among a few groups of sedentary hunter-gatherers. Among them, farming could have benefited the first adopters because it would have been easier to establish the private possession of cultivated crops and domesticated animals than for the diffuse wild resources on which hunter-gatherers relied.

"It is a lot easier to define and defend property rights in a domesticated cow than in a wild kudu," says Choi. "Farming initially succeeded because it facilitated a broader application of private property rights, not because it lightened the toil of making a living."

Source: Santa Fe Institute [October 11, 2019]

Social inequality in Bronze Age households

By: Thomas Schmitt Attorney on October 09, 2019 / comment : 0 Archaeology, Europe, Germany, Society, Western Europe

Archaeogenetic analyses provide new insights into social inequality 4000 years ago: nuclear families lived together with foreign women and individuals from lower social classes in the same household.

Illustration of Bronze Age Europeans [Credit: bunterhund]

Social inequality already existed in southern Germany 4000 years ago, even within one household, a new study published in the Science finds. Archaeological and archaeogenetic analyses of Bronze Age cemeteries in the Lech Valley, near Augsburg, show that families of biologically related persons with higher status lived together with unrelated women who came from afar and also had a high status, according to their grave goods.

In addition, a larger number of local but clearly less well-off individuals were found in the same cemeteries, which were small gravesites associated with single homesteads. The researchers conclude that social inequality was already part of households structures in that time and region. Whether the less well-off individuals were servants or slaves can only be speculated upon.

In Central Europe, the Bronze Age covers the period from 2200 to 800 BCE. At that time people acquired the ability to cast bronze. This knowledge led to an early globalization, since the raw materials had to be transported across Europe. In an earlier study, the current team had shown that, 4000 years ago, the majority of women in the Lech Valley came from abroad and may have played a decisive role in the transfer of knowledge. Supraregional networks were apparently fostered by marriages and institutionalized forms of mobility.

The current archaeological-scientific project was situated at the Heidelberg Academy of Sciences and led by Philipp Stockhammer from the Ludwig-Maximilians-Universitaet (LMU) in Munich together with Johannes Krause and Alissa Mittnik from the Max Planck Institute for the Science of Human History in Jena and the University of Tubingen. The researchers attempted to investigate the effects of this mobility and other concurrent changes.

The excavations south of Augsburg, which took place at the sites of Bronze Age homestead farms and their associated graveyards, enabled archaeologists to zoom into the Bronze Age in unprecedented resolution in order to investigate how the transition from the Stone Age to the Bronze Age affected the households of that time.

"Wealth was correlated with either biological kinship or foreign origin. The nuclear family passed on their property and status over generations. But at every farm we also found poorly equipped people of local origin," says Philipp Stockhammer, Professor of Prehistoric Archaeology at LMU Munich. This finding suggests a complex social structure of households, as is also known from Classical Greece and Rome.

In Roman times, slaves were also part of the family unit, but had a different social status. However, these people in the Lech Valley lived over 1500 years earlier. "This shows how long the history of social inequality in family structures goes back in time," Stockhammer continues.

Stable social structures over 700 years

It was already known that the first larger hierarchical social structures evolved in the Bronze Age. The findings of the current study were surprising in that social differences existed within a single household and were maintained over generations.

Grave goods can reveal the social status of the deceased to archaeologists. In the Lech Valley, weapons and elaborate jewelry were only found in the graves of closely related family members and women who came into the family from long distances, up to several hundred kilometers away. Other unrelated individuals of local origin were found in the same cemeteries without such high-status grave goods.

This study also succeeded in reconstructing for the first time family trees from prehistoric cemeteries spanning four to five generations. Surprisingly, however, these only included the male lineages. The female descendants apparently left the farms where they reached adulthood. The mothers of the sons, on the other hand, were all women who had moved in from afar.

"Archaeogenetics provides us with a completely new view of the past. Until recently, we would not have thought it possible to examine marriage rules, social structure and social inequality in prehistory," says Johannes Krause, Director of the Department of Archaeogenetics at the Max Planck Institute for Human History.

The archaeologists on the project were able to compare the degree of kinship with the grave goods and the location of the graves and show how couples and their children were buried. This was made possible by generating genome-wide data from more than 100 ancient skeletons, which allowed reconstructing family tress from prehistoric bone. Only the genetically unrelated local members of a household were buried without significant grave goods.

"Unfortunately, we cannot say whether these individuals were servants and maids or perhaps even enslaved," says Alissa Mittnik. "What is certain is that through the male lines, the farmsteads were passed from generation to generation and this system was stable over at least 700 years, across the transition from the Stone Age to the Bronze Age. The Lech Valley shows how early social inequality within individual households can be found."

Source: Ludwig-Maximilians-Universitat Munchen [October 09, 2019]

Inequality: What we've learned from the 'Robots of the late Neolithic'

By: Thomas Schmitt Attorney on September 18, 2019 / comment : 0 Archaeology, Eurasia, Europe, Middle East, Society

Seven thousand years ago, societies across Eurasia began to show signs of lasting divisions between haves and have-nots. In new research published in the journal Antiquity, scientists chart the precipitous surge of prehistoric inequality and trace its economic origins back to the adoption of ox-drawn ploughs.

A Canadienne ox at a historic village in New Brunswick, Canada [Credit: Amy Bogaard]

Their findings challenge a long-held view that inequality arose when human societies first transitioned from hunting and gathering to agriculture. According to the researchers, it was not agriculture per se that ushered in substantial wealth inequalities, but instead a transformation of farming that made land more valuable and labour less so.

"Ox drawn ploughs were the robots of the late Neolithic," explains co-author Samuel Bowles, an economist at the Santa Fe Institute. The oxen were a form of labour-saving technology that led to a decoupling of wealth from labour - a decoupling fundamental to modern wealth inequality. "The effect was the same as today: growing economic disparities between those who owned the robots and those whose work the robots displaced."

In the first of two companion papers, the researchers present new statistical methods for comparing wealth inequality across different kinds of wealth, different societies, in different regions, at different times in history. Their analysis of data from 150 archaeological sites reveals a steep increase in inequality in Eurasia from around 4,000 BC -- several millennia after the advent of agriculture.

"The surprise here isn't so much that inequality takes off later on, it's that it stayed low for such a long time," says lead author Amy Bogaard, an archaeologist based at the University of Oxford who is also an external professor at the Santa Fe Institute.

"The usual story -- that the societies that adopted agriculture became more unequal -- is no longer valid because we observed that some societies who adopted agriculture were remarkably egalitarian for thousands of years," says co-author Mattia Fochesato, an economist at Bocconi University.

Before around 4,000 BC, societies across the Middle East and Europe cultivated a patchwork of small garden plots, which Bogaard likens to present-day "allotments" in the UK. Families would have grown a variety cereal grains, as well as lentils, peas, and other pulse crops that needed to be harvested by hand. Notably, they would have tilled the soil by hand using hoes, in some cases also with the help of unspecialized cattle (such as aging milk cows) to pull ploughs, and carefully monitored their gardens during the growing season to protect them from wild animals. "It was quite a busy landscape, with lots of people working in and around these garden plots."

Humble ox or Neolithic robot? [Credit: Amy Bogaard]

Then something changed. Farmers who were well resourced enough to raise and maintain specialized plough oxen saw new opportunities in farming additional land. A single farmer with an ox team could cultivate ten times or more land than a hoe farmer, and would begin to acquire more and more land to cultivate. Those who owned land and ox teams also began to opt for more stress-tolerant crops, like barley or certain kinds of wheat, that didn't require much labour.

By the second millennium BC in many farming landscapes fields stretched to the horizon, and societies were deeply divided between wealthy landowners, who passed their holdings on to their children, and land-poor or landless families.

The mechanism that drove this change is detailed in an economic model in the researchers' second paper. It reveals a key distinction between farming systems where human labour was the limiting factor for production, versus systems where human labour was more expendable, and where land was the limiting factor.

"So long as labour was the key input for production, inequality was limited because families did not differ much in how much labor they could deploy to produce crops, " Fochesato explains. "But when the most important input became land, differences between families widened because land and other material forms of wealth could be accumulated and transmitted over generations. By chance, or force, or hard work, some families came to have a lot more than others. Then radical inequality arose."

The two new papers are part of a growing body of scientific research that is applying comparative economic measures to the archaeological record. Much of the work is part of Bowles' long-running series of interdisciplinary workshops on the origins of wealth inequality, which convene annually at the Santa Fe Institute. The new research supports previous findings by archaeologist Tim Kohler et al (Nature, 2017), which drew attention to a markedly greater wealth inequality in post-Neolithic Eurasia than in the Americas, where domesticated draft animals would not have been available.

One consequence of inequality, Bogaard notes, is that the most unequal societies tended to be more fragile and susceptible to political upheaval or climate change.

The takeaway for people today is that "if there are opportunities to monopolize land or other key assets in a production system, people will. And if there aren't institutional or other redistributive mechanisms, inequality is always where we're going to end up." Land is still a relevant asset, Bogaard says, "but there are many other kinds of assets now that we should think about people's capacity to own and benefit from."

Author: Jenna Marshall | Source: Santa Fe Institute [September 18, 2019]

Community size matters when people create a new language

By: Thomas Schmitt Attorney on July 17, 2019 / comment : 0 Anthropology, Human Evolution, Linguistics, Society

Why are languages so different from each other? After comparing more than two thousand languages, scientists noticed that languages with more speakers are usually simpler than smaller languages. For instance, most English nouns can be turned into plurals by simply adding -s, whereas the German system is notoriously irregular. Linguists have proposed that languages adapt to fit different social structures.

Credit: iStockphoto, Kronick

"But we actually don't know whether it is the size of the community that drives the difference in complexity," says lead author Limor Raviv from the Max Planck Institute for Psycholinguistics. Perhaps the bigger languages have simpler grammars because they cover larger geographical space and speakers are far from each other, or because large communities have more contact with outsiders. Together with her colleagues, Antje Meyer from the Max Planck Institute for Psycholinguistics and Radboud University and Shiri Lev-Ari from the Royal Holloway University of London, Raviv set out to test whether community size alone plays a role in shaping grammar.

'Wowo-ik' and 'wowo-ii'

To test the role of group size experimentally, the psycholinguists used a communication game. In this game, participants had to communicate without using any language they know, leading them to create a new language. The goal of the game was to communicate successfully about different novel scenes, using only invented nonsense words.

A 'speaker' would see one of four shapes moving in some direction on a screen and type in nonsense words to describe the scene (its shape and direction). The 'listener' would then guess which scene the other person was referring to, by selecting one of eight scenes on their own screen. Participants received points for every successful interaction (correct guesses). Participants paired up with a different person from their group at every new round, taking turns producing and guessing words.

At the start of the game, people would randomly guess meanings and make up new names. Over the course of several hours, participants started to combine words or part-words systematically, creating an actual mini-language.

For instance, in one group, 'wowo-ik' meant that a specific shape was going up and right, whereas 'wowo-ii' meant that the same shape was going straight up. With such a 'regular' system, it becomes easier to predict the meaning of new labels ('mop-ik' meant a different shape going up and right). Participants played in either 'small' groups of four participants or 'large' groups of eight participants. Would the large groups invent 'simpler' (more systematic) languages than the small groups?

Variability promotes structure

By the end of the experiment, the large groups had indeed created languages with more systematic grammars. "The pressure to create systematic languages is much higher in larger groups," explains Raviv. This is because there are more word versions in the larger groups. In order to understand each other, members of a large group must overcome this variability and develop systematic structure. So the more variability, the more it pushed people to make their language even simpler.

The researchers also found that the size of the group predicted how similar that group was to the other groups. All large groups reached similar levels of structure and communicative success. However, the small groups differed a lot from each other: some never developed systematic grammars, while others were very successful." This might mean that in the real world, larger languages are potentially more similar to each other than smaller languages," Raviv says.

"Our study shows that the social environment in which languages evolve, and specifically the number of people in the community, can affect the grammar of languages," concludes Raviv. "This could possibly explain why some languages have more complex grammar than others. The results also support the idea that an increase in human population size was one of the main drivers for the evolution of natural languages."

The study is published in the Proceedings of the Royal Society B: Biological Sciences.

Source: Max Planck Institute for Psycholinguistics [July 17, 2019]

Imitation breeds war in new evolutionary theory

By: Thomas Schmitt Attorney on June 29, 2019 / comment : 0 Anthropology, Human Evolution, Society

When anthropologists consider the origins of warfare, their evolutionary theories tend to boil it down to the resource-scarcity trifecta of food, territory and mates—three resources that would justify the loss of life and risk to a warring group of hunter-gatherers.

Credit: University of Colorado Denver

But researchers from University of Colorado Denver, University of British Columbia and University of Santiago, Chile, created an evolutionary mathematical model to unearth a fourth theory. They found that acculturation—the adoption and imitation of a victor's culture following defeat—could promote the evolution of intergroup conflicts. In other words, groups may evolve to fight for fighting's sake, despite the costs.

"Warriors" and "shepherds" in human evolution

"I've researched the evolution of cooperation and altruism—paradoxes in the conventional evolutionary theory of survival of the fittest—by group selection, but in this case, we wanted to understand the evolution of intergroup conflict," said Burton Simon, Ph.D., associate professor of mathematics at CU Denver, who has worked as a sort of "mathematical anthropologist" for the last decade.

The researchers' mathematical model is based on two classes of people: warriors, who specialize in intergroup conflicts and have a low birth rate, and shepherds, who cannot defend themselves but are highly reproductive. The amount of each within a group depended on the probability that an offspring becomes a warrior or shepherd, a cultural trait passed vertically from one generation to the next.

The study determined group dynamics through three types of events: group extinctions (a whole group dies, e.g., as the result of a drought or a bad crop), fissions (when an overly large group splits into two) and group conflicts due to their "belligerence" (assumed to increase a group's probability of trying to conquer another group). When groups fight in the model, the winner imposes its cultural traits on the loser or eliminates the group altogether. The belligerence of a group and the probability that they will impose their culture (acculturation tendency) are two of those traits.

"You need individuals who are shepherds to reproduce and individuals who are warriors to protect the group," said Simon. "But the right numbers of each can change over time in complicated and surprising ways."

Cultural evolution may promote the spread of conflict

How might these cultures thrive or die? Depending on the initial conditions of each group and which parameters (like acculturation and belligerence) were allowed to evolve, researchers found that sometimes groups fought each other into extinction. In other cases, the whole population reached a peaceful equilibrium.

But when researchers allowed all of the parameters to evolve, they found that acculturation coevolved with belligerence and warrior production. In other words, groups became more and more belligerent over time, and they forced their cultures on their victims instead of killing them.

That cultural evolution may promote the spread of conflict, even in cases where it may hurt both the groups and the individuals, is a theory that has received little attention. A mathematical model was one way to see how it could happen, said Simon.

"I realize mathematical anthropology sounds like an oxymoron," said Simon. "Most people who theorize about why there's so much conflict between human groups use economics and political science. But when you look at a hunter-gatherer society with a mathematical model, which forces you to state your assumptions precisely, the results can be enlightening."

Simon cautioned that the causes of today's conflicts are much too complex for a mathematical model to tackle, but his research is a glimpse into how imitation might indirectly breed conflict in evolutionary theory.

The study was published in the Proceedings of the National Academy of Sciences.

Author: Rachel Sturtz | Source: University of Colorado Denver [June 29, 2019]

New study shows how environmental disruptions affected ancient societies

By: Thomas Schmitt Attorney on June 18, 2019 / comment : 0 Archaeology, Climate Change, Earth Science, Society

LSU College of the Coast & Environment Distinguished Professor Emeritus John Day has collaborated with archeologists on a new analysis of societal development. They report that over the past 10,000 years, humanity has experienced a number of foundational transitions, or "bottlenecks." During these periods of transition, the advance or decline of societies was related to energy availability in the form of a benign climate and other factors.

Aerial view of the eruption of the volcano Grimsvotn in the south-east of Iceland [Credit: EPA/AdalSteinsson]

"Studying the factors that led to the advancement and contraction of past societies provides insight into how our globalized society might become more or less sustainable," Day said.

Day's collaborators include Joel Gunn of the University of North Carolina at Greensboro, William Folan of the Universidad Autonoma de Campeche in Mexico and Matthew Moerschbaecher of the Louisiana Oil Spill Coordinators Office. Gunn and Folan are Mayan archaeologists and Moerschbaecher is a graduate of LSU's oceanography program.

With the human population having exceeded the capacity of Earth's resources, this analysis suggests that a transition toward sustainability for the current energy-dense, globalized industrial society will be very difficult if not impossible without dramatic changes.

The authors say that these past transitions were caused by a combination of social, astronomical and biogeophysical events such as volcanic eruptions, changes in solar emissions, sea-level rise and ice volume, biogeochemical and ecological changes, and major social and technological innovations.

One example is the worldwide crisis that began in 536 AD, which was caused by three major volcanic eruptions within a decade. This event led to the destruction of half the population of Europe via the Black Death plague, starvation and wars. In China and the Mayan region, it led to crop failures, famine and plagues.

They found that when energy was abundant, societies expanded and prospered. Conversely, when energy sources declined, there was societal contraction and collapse. The previous example implies that changes are more likely to transpire due to planetary-scale disturbances and constraints, whether societal or environmental, and will likely lead to strong societal disruptions.

However, in the past, major changes sometimes moved toward a more sustainable social organization. For example, after one disruption, the Mayans switched to a more efficient use of energy and marine transportation and, at the time of European contact, they were leading a sustainable lifestyle.

The study appears in BioPhysical Economics and Resource Quality.

Source: Louisiana State University [June 18, 2019]