Genomes reveal startling diversity in the ancient world
A new study shows that the ancient world was much more culturally diverse than previously thought.
The analysis of DNA samples from ancient grave sites in Rome shows that the city was populated by people from all over the ancient world.
Two thousand years ago, the Roman Empire’s trade routes stretched from North Africa to Asia, and new immigrants poured in every day, both by choice and by force.
The study shows these far-flung connections became embedded in the genomes of the Romans.
People from the city’s earliest eras and from after the Western empire’s decline in the fourth century genetically resembled other Western Europeans.
But during the imperial period most of the DNA sampled had Eastern Mediterranean or Middle Eastern ancestry.
The study, published in the journal ‘Science’ traces 12,000 years of history using genomes from 127 people buried at 29 archaeological sites in and around Rome.
The researchers from Rome, Vienna and Stanford universities sourced hundreds of samples from dozens of previously excavated sites and extracted DNA from the skeletons’ ear bones. Geneticists then sequenced and analyzed their DNA.
The study said that the oldest genomes came from three hunter-gatherers who lived 9000 to 12,000 years ago and genetically resembled other hunter-gatherers in Europe at the time.
Later genomes showed the Romans changed in step with the rest of Europe, as an influx of early farmers with ancestry from Anatolia (in modern day Turkey) reshaped the genetics of the entire region some 9000 years ago.
But Rome went its own way from 900 BC to 200 BC.
The settlement grew from a small town into an important city. During this growth, migration increased.
This is reflected in the fact that some genome samples which genetic markers resembling those of modern Italians and others have markers reflecting ancestry from the Middle East and North Africa.
That diversity increased even more as Rome became an empire. Between 27 BC and 300 AD, the city was the capital of an empire of 50 million to 90 million people, stretching from North Africa to Britain to the Middle East.
Its population grew to more than a million people.
The study suggests the vast majority of immigrants to Rome came from the East. Of 48 individuals sampled from this period, only two showed strong genetic ties to Europe. Another two had strong North African ancestry. The rest had ancestry connecting them to Greece, Syria, Lebanon, and other places in the Eastern Mediterranean and Middle East.
The study says that once the empire split in two and the eastern capital moved to Constantinople (modern day Istanbul, Turkey) in the fourth century AD, Rome’s diversity decreased.
Trade routes sent people and goods to the new capital, and epidemics and invasions reduced Rome’s population to about 100,000 people.
Invading barbarians brought in more European ancestry. Rome gradually lost its strong genetic link to the Eastern Mediterranean and Middle East. By medieval times, city residents again genetically resembled European populations.
One of the researchers, Stanford University geneticist Jonathan Pritchard said that people imagine that the amount of migration we see nowadays is a new thing.
“But it’s clear from ancient DNA that populations have been mixing at really high rates for a long,” Prof Pritchard said.