It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Monday, April 14, 2025
Archaeologists measured and compared the size of 50,000 ancient houses to learn about the history of inequality -- they found that it’s not inevitable
Three excavated Classic period (ca. 550–750 CE) houses at El Palmillo (Valley of Oaxaca, Mexico). Bottom: the largest and most elaborate residential structure (Platform 11). Top right: a less elaborate residence (Structure 35). Top Left: a smaller residence (Terrace 925).
Credit: Image credit: Linda Nicholas and Gary Feinman.
We’re living in a period where the gap between rich and poor is dramatic, and it’s continuing to widen. But inequality is nothing new. In a new study published in the journal PNAS, researchers compared house size distributions from more than 1,000 sites around the world, covering the last 10,000 years. They found that while inequality is widespread throughout human history, it’s not inevitable, nor is it expressed to the same degree at every place and time.
“This paper is part of a larger study in which over 50,000 houses have been analyzed to use differentials in house sizes as a metric for wealth inequality over time, on six continents,” says Gary Feinman, the MacArthur Curator of Mesoamerican, Central American, and East Asian Anthropology at the Field Museum in Chicago, and the paper’s lead author. “This is an unprecedented data set in archaeology, and it allows us to empirically and systematically look at patterns of inequality over time.”
The paper Feinman led delves into a comparison of the extent of inequality at different localities (mostly archaeological) to figure out how things changed over time. “While there is not one unilinear sequence of change in wealth inequality over time, there are interpretable patterns and trends that cross-cut time and space. What we see is not just noise or chaos,” says Feinman.
The variation that the researchers found challenges long-held views across history and the social sciences that we can use ancient Greece and Rome, or the medieval history of Europe as generalized representations of humanity’s past. “There are a lot of things that have been presumed for centuries— for example, that inequality rises inevitably,” says Feinman. “The traditional thinking expects that once you get larger societies with formal leaders, or once you have farming, inequality is going to go way up. These ideas have been held for hundreds of years, and what we find is that it’s more complicated than that— high degrees of inequality are not inevitable in large societies. There are factors that may make it easier to happen or increase to high degrees, but these factors can be leveled off or modified by different human decisions and institutions.”
“Variability in the sizes of houses may not be the full extent of wealth differences, but it's a consistent indicator of the degree of economic inequality that can be applied across time and space,” says Feinman. “I know from my own archaeological fieldwork in the Valley of Oaxaca, Mexico, that almost always, the larger the house, the more elaborate the house, with special features and thicker walls.”
To quantify and compare economic inequality in different places, at different points in history, the researchers used the variable distributions of house sizes at more than 1000 settlements to calculate a Gini coefficient for each site conducted statistical analyses in which they examined the relationship between the amount of inequality in a society and the political complexity of that society. The Gini coefficient is a commonly employed metric to assess inequality that ranges between 0 (complete equality) and 1 (maximal inequality).The coefficients for each locality were then compared across time and space to examine trends in inequality and assess how it varied in relation to population, political organization, and other potential causal factors.
The investigators then looked at these trends in the Gini values in the context of the size of the sites that were compared and how complex the hierarchical structure of governance was. They found that even while populations have risen over the years, inequality hasn’t always increased in a uniform way.
“The measure of inequality we found in these sites is quite variable, which suggests that there’s not one homogenized pattern,” says Feinman. In other words, contrary to traditional scholarly thinking, there’s no one-size-fits-all explanation for why societies become economically unequal.
“Human choice and governance and cooperation have played a role in damping down inequality at certain times and places, and that is what accounts for this variability in time and space,” says Feinman. “And if inequality isn't inevitable when human aggregations get larger and governmental structures get more hierarchical, then there is a suite of implications for how we view the present and how we look at the past. Although history has shown us that elements of technology and population growth can raise the potential for inequality at certain times and places, that potential is not always realized, as people have implemented leveling mechanisms and systems of governance that mute that potential. The often-expressed views that certain economic, demographic, or technological conditions or factors make great wealth disparities inevitable simply are not borne out by our global past.”
###
Gary Feinman directing the excavations in the Platform 11 residence in El Palmillo.
Gary Feinman and a crew member exposing a plaster floor on Terrace 925 in El Palmillo.
If the archaeological record has been correctly interpreted, stone alignments in Tanzania’s Olduvai Gorge are remnants of shelters built 1.7 million years ago by Homo habilis, an extinct species representing one of the earliest branches of humanity’s family tree.
Archaeological evidence that is unambiguously housing dates to more than 20,000 years ago—a time when large swaths of North America, Europe and Asia were covered in ice and humans had only recently begun living in settlements.
Between that time and the dawn of industrialization, the archaeological record is rich not only with evidence of settled life represented by housing, but also with evidence of inequality.
In a PNAS Special Feature published today, scholars from around the world draw from a groundbreaking archaeological database that collects more than 55,000 housing floor area measurements from sites spanning the globe—data that support research demonstrating various correlations between housing size and inequality.
“Archaeologists have been interested in the study of inequality for a long time,” explains Scott Ortman, a University of Colorado Boulder associate professor of anthropology who partnered with colleagues Amy Bogaard of the University of Oxford and Timothy Kohler of the University of Florida to bring together the PNAS Special Feature. “For a long time, studies have focused on the emergence of inequality in the past, and while some of the papers in the special feature address those issues, others also consider the dynamics of inequality in more general terms.”
“They use this information to identify the fundamental drivers of economic inequality using a different way of thinking about the archaeological record—more thinking about it as a compendium of human experience. It’s a new approach to doing archaeology.”
Patterns of inequality
Ortman, Bogaard and Kohler also are co-principal investigators on the Global Dynamics of Inequality (GINI) Project funded by the National Science Foundation and housed in the CU Boulder Center for Collaborative Synthesis in Archaeology in the Institute of Behavioral Science to create the database of housing floor area measurements from sites around the world.
Scholars then examined patterns of inequality shown in the data and studied them in the context of other measures of economic productivity, social stability and conflict to illuminate basic social consequences of inequality in human society, Ortman explains.
“What we did was we crowdsourced, in a sense,” Ortman says. “We put out a request for information from archaeologists working around the world, who knew about the archaeological record of housing in different parts of world and got them together to design a database to capture what was available from ancient houses in societies all over world.”
Undergraduate and graduate research assistants also helped create the database, which contains 55,000 housing units and counting from sites as renowned as Pompeii and Herculaneum, to sites across North and South America, Asia, Europe and Africa.
“By no stretch of the imagination is it all of the data that archaeologists have ever collected, but we really did make an effort to sample the world and pull together most of the readily available information from excavations, from remote sensing, from LiDAR,” Ortman says.
The housing represented in the data spans non-industrial society from about 12,000 years ago to the recent past, generally ending with industrialization. The collected data then served as a foundation for 10 papers in the PNAS Special Feature, which focus on the archaeology of inequality as evidenced in housing.
Housing similarities
In their introduction to the Special Feature, Ortman, Kohler and Bogaard note that “economic inequality, especially as it relates to inclusive and sustainable social development, represents a primary global challenge of our time and a key research topic for archaeology.”
“It is also deeply linked to two other significant challenges. The first is climate change. This threatens to widen economic gaps within and between nations, and some evidence from prehistory associates high levels of inequality with lack of resilience to climatic perturbations. The second is stability of governance. Clear and robust evidence from two dozen democracies over the last 25 years that links high economic inequality to political polarization, distrust of institutions and weakening democratic norms. Clearly, if maintenance of democratic systems is important to us, we must care about the degree of wealth inequality in society.”
Archaeological evidence demonstrates a long prehistory of inequality in income and wealth, Ortman and his colleagues note, and allows researchers to study the fundamental drivers of those inequalities. The research in the Special Feature takes advantage of the fact “that residences dating to the same chronological period, and from the same settlements or regions, will be subject to very similar climatic, environmental, technological and cultural constraints and opportunities.”
Several papers in the Special Feature address the relationship between economic growth and inequality, Ortman says. “They’re thinking about not just the typical size of houses in a society, but the rates of change in the sizes of houses from one time step to the next.
“One thing we’ve also done (with the database) is arrange houses from many parts of the world in regional chronological sequences—how the real estate sector of past societies changed over time.”
The papers in the Special Feature on topics including the effects of land use and war on housing disparities and the relationship between housing disparities and how long housing sites are occupied. A study that Ortman led and conducted with colleagues from around the world found that comparisons of archaeological and contemporary real estate data show that in preindustrial societies, variation in residential building area is proportional to income inequality and provides a conservative estimator for wealth inequality.
“Our research shows that high wealth inequality could become entrenched where ecological and political conditions permitted,” Bogaard says. “The emergence of high wealth inequality wasn’t an inevitable result of farming. It also wasn’t a simple function of either environmental or institutional conditions. It emerged where land became a scarce resource that could be monopolized. At the same time, our study reveals how some societies avoided the extremes of inequality through their governance practices.” The researchers argue that “the archaeological record also shows that the most reliable way to promote equitable economic development is through policies and institutions that reduce the covariance of current household productivity with productivity growth.”
GINI Project data, as well as the analysis program developed for them, will be available open access via the Digital Archaeological Record.
While serving as a visiting professor in Benevento, outside of Naples, Italy, Adrian Bejan noticed something about the local architecture: All the roofs looked the same. With what seemed like too-shallow peaks on smaller, older structures clustered together, perhaps it was just the style of the times.
Or perhaps the ancient Roman builders were on to something. An expert in thermodynamics and the movement and flow of heat, Bejan, the J.A. Jones Distinguished Professor of Mechanical Engineering at Duke, was the perfect person to sleuth out an answer.
Sitting down with pencil and paper, Bejan went through the equations and calculations that govern heat flow and transfer within two similar shapes: a long roof with a triangular cross section and a circular cone. The results, obtained in collaboration with Pezhman Mardanpour, assistant professor of mechanical and materials engineering at Florida International University, were published online March 28 in the journal International Communications of Heat and Mass Transfer. They showed that there are indeed roof shapes that maximize heat retention—the older generation of Italian architects knew what they were doing.
“Pockets of air aregood insulators, and attics are basically just differently shaped pockets of air,” Bejan said. “While energy conservation is a popular buzzword today, in years long past it was a matter of survival.”
The details of how squat or tall a roofline determines how the air within it will act. Given a single peak on an A-frame or circular cone, if that peak is less than three feet tall, the air will flow smoothly and uniformly across it like water careening down the side of a sink. But if the peak is more than three feet tall, the air will tumble around chaotically like smoke waving wildly in the wind.
Based on the physics of these airflows and heat transfer, if a roof peak is shorter than roughly three feet, it should be about three or four times wider than it is tall to minimize heat loss. And if a roof peak is taller than three feet, it should be an equilateral triangle with a height-to-width ratio of one.
Perhaps unsurprisingly, these are roughly the same ratios that can be found in countless older, modest dwellings created across the world. And they are pretty close to the rooflines that Bejan saw that day in southern Italy.
“This type of insight is not hard to rationalize, but it’s easy to overlook even though there are examples everywhere,” Bejan said. “It’s important for our students—and their professors—to open their imaginations and ask why things are the way that they are.”
While Bejan doubts that architects from days gone by were applying thermodynamics to their roof designs, he doesn’t think their shapes were accidental, either. It isn’t difficult to imagine, he says, discovering that one neighbor’s home is warmer than another’s and copying its design repeatedly across many years.
It’s a lesson, he says, that modern architects could stand to consider as well.
“Today’s homes and buildings are being designed to be as energy efficient as possible,” Bejan said. “But to my knowledge, nobody is considering the physical shape of the building, or any ‘thing’ like a vehicle or animal, as a variable that could help with that efficiency, and perhaps we should be.”
This work was supported by the U.S. Air Force Office of Scientific Research (FA9550-23-1-0716, FA9550-22-1-0525.
“Why people shape roofs the same way.” A. Bejan, P. Mardanpour. International Communications in Heat and Mass Transfer, Volume 164, Part B, May 2025, 108909. DOI: 10.1016/j.icheatmasstransfer.2025.108909
Journal
International Communications in Heat and Mass Transfer
No comments:
Post a Comment