Architectural blueprints of thousands of ancient dwellings reveal horrifying patterns of inequality throughout human history

Archaeologists have created a global database of more than 55,000 residential floor area measurements from a variety of sites around the world, with the aim of examining how inequality grew in pre-industrial societies. Initial findings reveal that wealth gaps tended to emerge where land became a scarce and monopolized resource, but in some societies equality was protected by shared governance mechanisms.

If current interpretations of the archaeological topographic record are correct, the earliest structures identified with our ancestors—stone lines discovered in Oldowan Canyon in Tanzania and belonging to the Homo habilis lineage 1.7 million years ago—may have served as primitive shelters. But archaeological evidence of permanent habitation dates back only to about 20,000 years ago, when much of North America, Europe, and Asia was covered in ice and human communities were beginning to establish permanent settlements.

From that point in time until the beginning of industrialization, the database provides the richest evidence of permanent residence and the rise of social inequality. In a special article in PNAS, researchers from various universities use this data to examine correlations between residence size and measures of inequality.

Scott Ortman of the University of Colorado at Boulder, who led the collaboration with Amy Bogart of the University of Oxford and Timothy Koller of the University of Florida, explains: “Archaeologists have been interested in studying inequality for a long time. While some of the articles in the supplement deal with the development of inequality in the past, others focus on the general dynamics of this phenomenon.” He says the new approach treats the archaeological record as a broad representation of human experience that seeks to uncover the drivers of economic inequality.

Patterns of inequality

Ortman, Bogaard, and Kohler are also principal investigators on the NSF-funded Global Dynamics of Inequality (GINI) project, which serves as a synthesis center at the Behavioral Sciences Institute at CU Boulder. The project recruited archaeologists from around the world to contribute data from existing studies, which were reviewed and consolidated into a central repository. Graduate research assistants and graduate and undergraduate students also contributed to the database, which now includes over 55,000 residential units from sites ranging from Pompeii and Herculaneum to suburban communities in the Americas, Europe, Asia, and Africa.

“This is not all the data that archaeologists have ever collected,” Ortman notes, “but we tried to sample the world and include as much information as is known from excavation studies, remote sensing, and lidar.”

The database focuses on pre-industrial societies from 12,000 BC to the beginning of the Industrial Revolution, and serves as the basis for ten articles in the PNAS supplement dealing with the archaeology of inequality as reflected in housing.

Similarity in residential patterns

In the introduction to the supplement, they write: “Economic inequality, especially in the context of inclusive and sustainable social development, constitutes a major global challenge of our time and a key research topic in archaeology.” They also note the connection to climate change—which may exacerbate economic disparities—and the connection to governmental stability, as recent studies from fourteen democracies indicate that high inequality is linked to political fragmentation and decreased trust in institutions.

The articles discuss the relationship between economic growth and inequality, land use mechanisms, the impact of wars on housing disparities, and the length of time settlements remain inhabited. Research led by Ortman in collaboration with an international team found that in pre-industrial settlements, the dispersion of housing size is proportional to income disparities, and is a conservative estimate of wealth inequality.

“Our research shows that high inequality becomes entrenched in situations where land becomes a scarce resource that can be monopolized,” concludes Bogaard, “but also reveals how some societies have managed to mitigate disparities through flexible governance mechanisms.”

Researcher Kohler and his team also point out that the archaeological record shows that a reliable way to promote equitable development is to adopt policies and institutions that reduce the dependence of family fertility on developments in economic growth.