By putting the Roman DNA Project out to the public, I made the choice to focus on the big picture, on what the results will tell me in general about the people of Imperial Rome. In a grant proposal to an agency like the NSF, NEH, or Wenner-Gren, though, I would have spelled out my hypotheses more fully and in more technical terms. This post provides a bit more information on the specific goals of the Roman DNA Project, without getting too jargony-grant-speak-y.
Goal 1 – Use mtDNA analysis to more fully understand the demographics of the population of Imperial Rome. For this pilot phase of the project, we’ll be looking at mitochondrial DNA to learn more about the maternal genetic lines of the Romans – both the locals and the people that previous isotope study suggested were immigrants. Very broadly, mtDNA (which is passed on, unchanged, from mother to daughter) will give us additional information about the geographic backgrounds of the people buried in the two cemetery populations, contributing further to discussions about demography in Rome. We expect to find mostly central European haplogroups, but there may be some African, Iberian, and Near Eastern genes. In combination with the previous Sr/O/Pb (and to some extent C) isotopes, though, we may be able to say with more confidence that a particular person originated in North Africa, Spain, Asia Minor, etc. Depending on the data produced, we’ll learn more about the origins of the population of Imperial Rome (tracing it back multiple generations) and the origins of specific people at Rome (immigrants or possibly one generation removed).
Goal 2 – Use mtDNA analysis to investigate the genetic diversity of the Republican population of Rome. In addition to learning more about the genetic background of the Imperial population, we plan to look at a sample of people from the earlier Republican period. A new theory has been proposed recently about the Roman Republic, with the suggestion that the population was highly mobile rather than sedentary peasants – perhaps even as mobile as people were in the Empire. Looking at mtDNA from the Republican samples (combined with previous Sr/O isotopes) will tell us a lot about the geographic origins of the population, namely whether there was significant gene influx prior to the Empire. Granted, the Republican sample is a small one, but the data that result should be of great interest to classical historians and demographers and will pave the way for future studies of Republican-era skeletons.
Goal 3 – Use mtDNA analysis to learn more about female mobility in the Empire. We’re also choosing mtDNA for this pilot phase specifically because it’s inherited from one’s mother. The mobility of females is a popular question in classics – many people think that women weren’t often taken as slaves and that they didn’t have the freedom to move like men did. My recent EAA paper compared Sr/O data from M1s and M3s of female immigrants to Rome; I found that women did move, and that some moved multiple times during their lives. Another interesting question that this DNA project will start to answer is about genetic diversity among males and females. The Roman family was often neolocal in residence (the nuclear family lived separately) but patrilocal in burial (people were buried with their father’s/father-in-law’s family). In a Roman burial context, we might expect more genetic diversity in females who were marrying into a family. But more men moved around the Empire because of the military and slavery, so a cemetery population may have more diversity in males, especially if the cemetery was specifically for slaves. Eventually, it would be great to do some Y-DNA testing, to look into the genetic diversity of males as well. But the mtDNA will give us a good head-start on answering questions of sex-specific mobility.
Future Goal – Use DNA, isotope, and palaeopathological analysis to answer questions about disease ecology. Malaria has long been a topic of interest to classicists; some DNA work has been done in the past (see, for example, Sallares’ 2002 book Malaria and Rome) and shows that it’s possible to identify P. falciparum, the organism that causes malaria, within a skeleton. DNA analysis, though, could also let me look for genetic anemias like thalassemia, sickle-cell, and G6PD, which confer some protection from malaria and were likely common in the Mediterranean. Interestingly, I recently charted the oxgyen isotope ratios for people with and without porotic hyperostosis, a bone pathology resulting from anemia, and there is a statistical correlation between high oxygen ratios and presence of porotic hyperostosis. Higher oxygen ratios mean warmer climates, and may also mean geographical areas with higher (or different) parasite loads. There’s definitely promise in looking at the disease ecology of Rome/Italy at a molecular level, so I’m hoping that we successfully extract DNA in this pilot phase.