Historical story

Isotope research missing link for migration research in antiquity?

The view of migration in classical antiquity has been changing in recent years. Humans and animals are turning out to be more mobile than we thought, according to new research techniques. But while one historian is jubilant about these techniques, another is skeptical.

Thanks to research into isotopes and ancient DNA, new information about antiquity is rapidly becoming available to us. For example, when it comes to migration, the theme of this year's Week of Classics. The research results seem to indicate that people were a lot more mobile we thought. But how reliable are these techniques? During a debate about new research techniques in the National Museum of Antiquities, scientists share their vision.

You are what you eat

Today we can look at the DNA of human remains and conduct isotope research on the tooth enamel of skeletons. This is a recent development:the oldest isotope research on teeth from Roman times dates back to 2007. DNA tells where ancestors came from, but isotopes even reveal individual history:your tooth enamel shows whether you spent your entire childhood in the same place or not. Lisette Kootker of the VU conducts archaeological isotope research, particularly with human and animal skeletal remains from Dutch soil, and explains what can be seen in tooth enamel:

“We are what we eat. Everything you eat and drink during your life contains chemical elements that end up in your bones, nails, hair and teeth. Each element consists of isotopes that are chemically almost identical to each other, but differ in mass. Isotopes are found in bedrock and end up in our tooth enamel via the plants and animals we eat. On the basis of the tooth enamel, we determine which locations would be suitable.”

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However, different areas can have the same bedrock, so scientists can't say exactly where someone came from. Kootker:“You can determine where the person does not come from; isotope research is therefore research that excludes.” This limitation is often overlooked when coming up with catchy headlines for an article about new research results.

Rens Tacoma, antiquarian at Leiden University, is therefore somewhat skeptical about the new research techniques:“In addition, the results are of course very nice, but I think we overestimate their importance. This type of examination is expensive and time-consuming, so it is only performed on a limited number of teeth. How representative is the outcome of, for example, 61 examined skeletons from a city like Rome where perhaps a million people lived during the Imperial era?”

The historian himself has conducted years of research into migration flows within the early Roman imperial period (first three centuries AD). He mainly analyzed tomb inscriptions stating the origin of the deceased. “The advantage of this source is that it is not just a single case, but thousands. The inscriptions certainly have disadvantages as a source, but with such numbers you can start looking at the connections. This is a lot more difficult with isotope research.”

Wrong interpretation

The research Tacoma cites is the first isotope research for the Roman period and also deals with migration (by T.L. Prowse, 2007). Prowse saw that 13 of the 61 were skeletons of children who were not born in Rome but had moved to the Roman city during their childhood. The conclusion was then that family migration was much more common than expected. Our view on migration, that it was mainly young men looking for work, should therefore be overhauled.

Tacoma disagrees and he says he is not alone:​​“There has been a lot of commentary on this conclusion because it is far too short-sighted. First, with such a small number of skeletons examined, you cannot make general statements about migration, especially at a time when cremation was the norm. Second, the author failed to take into account the fact that children could end up in Rome in other ways than with family, for example as slaves.”

And which area actually falls under Rome? The city has also grown over the centuries. There is not always clarity about area boundaries in general, Kootker also points out:“When were you actually a 'local' and when did you come from far away? And what was far, before that time? People easily traveled 40 kilometers a day.”

When the area boundaries shift and the data from these areas are interpreted differently, the research results turn out very differently. And with it the claims about migration. Tacoma:“Prowse's claim to revise the migration models was too extreme. But most isotope studies, and I've read quite a few, don't make such big claims.”

Revolution or not?

Some scientists have labeled isotope and DNA research, along with Big Data, a scientific revolution. But Tacoma disagrees:“I certainly do not deny that these new techniques are important in historical research and also for research into migration, but this importance is grossly exaggerated. It has too many limitations and the data is far from hard, which means that researchers have to interpret it.”

Historian Jona Lendering also addresses this subject in his public booklet for the Week of the Classics 2019. He expects that archaeologists will view exceptional finds differently, such as in his example of a Roman bronze coin, which was excavated in Japan in 2013:' A gold item could have been a trade item, but a bronze item has little value. More likely, a Roman had it somewhere in his luggage and unknowingly took it with him. If this is correct, then a bronze coin could be a clue to a Roman in East Asia. This idea, that a Roman in Japan was possible at all, is new', according to his book.

"The fact that scientists no longer think that the coins ended up in Japan in the Middle Ages, but are seriously considering the possibility of Romans in Japan, is related to the way in which the heuristics (the search directions) have been changed by DNA research," he added. Lendering. For example, a Roman slave was found in Vignaro, Italy, whose DNA indicated an East Asian origin. According to Lendering, it is no longer a curiosity but an important piece of evidence. Tacoma:“The conclusion from that study has been heavily criticized. The DNA says something about ancestors, not that the slave came from Japan, so what does this actually say?”

“The Vignaro excavation itself has nothing to do with the currency in Japan, but the DNA revolution is changing our view of prehistory and forcing us to look differently at the time that follows, antiquity. Clues like Vignaro suggest that adjustments for the heuristics for Antiquity do indeed need to be adjusted. If this happens, and it seems like it, we will look differently at Roman coins and glass and the like that have been found in Japan," Lendering responds.

DNA and isotope research is still in its infancy and that includes discussions and teething problems. And perhaps also the naive belief in progress with which it is often approached, according to Tacoma. Time and research results will tell.