Ancient Skulls Shed Light on Migration in the Roman Empire

Skeletal evidence shows that, hundreds of years after the Roman Republic conquered most of the Mediterranean world, coastal communities in what is now south and central Italy still bore distinct physical differences to one another – though the same could not be said of the area around Rome itself.

Using state-of-the-art forensic techniques, anthropologists from North Carolina State University and California State University, Sacramento examined skulls from three imperial Roman cemeteries: 27 skulls from Isola Sacra, on the coast of central Italy; 26 from Velia, on the coast of southern Italy; and 20 from Castel Malnome, on the outskirts of the city of Rome. The remains at the cemeteries in both Isola Sacra and Velia belonged to middle-class merchants and tradesmen, while those from Castel Malnome belonged to manual laborers. All of the remains date from between the first and third centuries A.D.

The researchers took measurements of 25 specific points on each skull using a “digitizer,” which is basically an electronic stylus that records the coordinates of each point. This data allowed them to perform shape analysis on the skulls, relying on “geometric morphometrics” – a field of study that characterizes and assesses biological forms.

“We found that there were significant cranial differences between the coastal communities, even though they had comparable populations in terms of class and employment,” says Ann Ross, a professor of anthropology at NC State and co-author of a paper on the work.

“We think this is likely due to the fact that the area around Velia had a large Greek population, rather than an indigenous one,” says Samantha Hens, a professor of biological anthropology at Sacramento State and lead author of the paper.

In addition, the skulls from Castel Malnome had more in common with both coastal sites than the coastal sites had with each other.

“This likely highlights the heterogeneity of the population near Rome, and the influx of freed slaves and low-paid workers needed for manual labor in that area,” Hens says.

“Researchers have used many techniques – from linguistics to dental remains – to shed light on how various peoples moved through the Roman Republic and the Roman Empire,” Ross says. “But this is the first study we know of in which anyone has used geometric morphometrics to evaluate imperial Roman remains.

“That’s important because geometric morphometrics offers several advantages,” Ross says. “It includes all geometric information in three-dimensional space rather than statistical space, it provides more biological information, and it allows for pictorial visualization rather than just lists of measurements.”

“The patterns of similarities and differences that we see help us to reconstruct past population relationships,” Hens says. “Additionally, these methods allow us to identify where the shape change is occurring on the skull, for example, in the face, or braincase, which gives us a view into what these people actually looked like.”

The paper, “Cranial Variation and Biodistance in Three Imperial Roman Cemeteries,” is published in the International Journal of Osteoarchaeology.

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Note to Editors: The study abstract follows.

“Cranial Variation and Biodistance in Three Imperial Roman Cemeteries”

Authors: Samantha M. Hens, California State University, Sacramento; and Ann H. Ross, North Carolina State University

Published: June 1, International Journal of Osteoarchaeology

DOI: 10.1002/oa.2602

Abstract: Ancient Roman populations are expected to exhibit considerable biological variation due to extensive trade networks and migration patterns throughout Europe and the circum-Mediterranean. The purpose of this research is to examine regional biological variation in Italy during Imperial Roman times (I-III Centuries AD) using three samples exhibiting distinctive class and economic systems. The individuals buried at Isola Sacra and Velia represent middle class tradesmen and merchants from coastal port populations from central and southern Italy, respectively; while the individuals from Castel Malnome represent an inland population near Rome of freed slaves and other lower class individuals, involved in heavy labor associated with salt production. Data were recorded from 25 three-dimensional cranial coordinate landmarks and analyzed using Procrustes Superimposition and associated multivariate statistics in MORPHOJ.

Procrustes ANOVA statistics were unable to detect any significant group differences for centroid size (p=0.595); but did detect differences in shape (p=0.0154), suggesting some variation between the three samples. Canonical variates analyses based on Procrustes distance values suitable for small sample sizes indicated that while Castel Malnome was not significantly different from either of the coastal sites (Isola Sacra, p=0.2071 and Velia, p=0.8015); Isola Sacra and Velia were significantly different (p=0.0119). The similarity of Castel Malnome to the other sites may reflect inherent heterogeneity in the sample, as it represents a group of freed slaves likely originating from various geographic locations. The separation of the two coastal sites is not unexpected, as Velia’s location was influenced by an influx of Greek populations in the southern Italian peninsula. This work supports previous studies using traditional craniometrics and dental metrics showing group similarity across the Italian peninsula and a separation between more northern and southern groups.