Ancient DNA sheds some light on mystery

Migrants from Southern Europe were the likely source of distinctive architecture and pottery associated with the ancient Philistines, an analysis of ancient genomes reveals.

According to the Hebrew Bible, the Philistines occupied five separate city-states along the coast of modern-day Israel and the Gaza Strip.

Archaeologists trace the start of the Philistine era to a period in the twelfth century BCE, when unique Philistine artefacts blossomed in the archaeological record at three known Philistine cities. 

The reason for the sudden cultural shift is a long-standing mystery.

One theory is that a population known as the “Sea Peoples” brought the culture with them from Aegean civilisations in ancient Greece and its surrounds. Indeed, Philistine pottery closely resembles pottery found in the Aegean.

Others have suggested immigrants from Cyprus, Anatolia in modern-day Turkey, Italy, or elsewhere were responsible. 

Another theory is that there were no migrants at all. Ideas adopted from foreign cultures could have diffused into the region and been adopted by the locals.

Michal Feldman from the Max Planck Institute for the Science of Human History in Jena, Germany, and her colleagues wanted to put these competing theories to the test.

They gathered skeletal remains found in grave sites in the ancient Philistine port of Ashkelon that date to 3,000 to 3,500 years ago, at the transition between the Bronze Age and the Iron Age when Philistine culture appeared.

Ancient DNA analysis has been a boon for uncovering relationships between prehistoric peoples. But the hot, humid conditions in the middle east are far from favourable when it comes to preservation of millennia-old DNA.

Almost none of the more than 100 bones contained DNA. But as luck would have it, scientists elsewhere had just discovered that the petrous bone in the inner ear was particularly good at preserving ancient DNA.

“This really changed everything for us, because we managed to get more individuals – enough to do this analysis,” says Feldman.

In total, ancient DNA was extracted from 10 individuals: three from pre-Philistine Bronze age individuals, four infants from the early Iron Age in the twelfth century BCE, and three later Iron Age individuals from around the tenth century BCE.

The four infants turned out to be crucial. Compared to the Bronze-age individuals, and even the later Iron Age individuals, the twelfth century infants had a distinct genetic profile. This was evidence of an influx of genes from outside of the region at precisely the time when Philistine culture took off.

By the late Iron Age, all genetic signs of the migrants had vanished. ““We almost don’t see any trace of this ancestry in the later Iron Age,” says Feldman. “They’re almost identical to the Bronze Age people.”

So, although the arrival of the immigrants heralded drastic cultural changes that persisted in Philistia for about 600 years, they were likely a minority that was quickly absorbed into the population, diluting out their genetic contribution.

“They mixed in the local populations quite quickly,” says Feldman. “That was a bit surprising.”

Because of that rapid integration, the researchers were lucky to have seen the genetic blip at all, Feldman adds. “We could have missed it if we only had the later Iron Age individuals,” she says.

The mystery of where the immigrants arrived from remains. The genetics of the four infants point are similar to ancient genomes from the same time period in Greece and Sardinia, but also the Iberian Peninsula.

To narrow down where in Southern Europe the immigrants hailed from, more 3000-year-old skeletons – ancient DNA intact – are required.

“It will be really cool to get samples for places like Cypress and from parts of Anatolia in present-day Turkey and other parts of Europe that we don’t have samples yet from,” says Feldman.

The study is published in the journal Science Advances.

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