Wednesday, November 13, 2019

The Genetics of Rome, Mesolithic to Modern

Fabulous new data set of 127 genomes from Rome, spanning the Mesolithic to Early Modern periods, has just been published in Science by Margaret Antonio and colleagues. This is not a lot of data for such a big problem, but I think the results are still very interesting.

# of
6,000 BC
Similar to all of Western Europe
6000-3500 BC
Mass influx of Anatolian farmers
Copper Age
3500-2300 BC
Rebound of Mesolithic ancestry
Bronze Age
2300-900 BC

Iron Age &
900-27 BC
First appearance of Steppes ancestry and North African ancestry, varying between individuals. Population resembles modern Mediterranean population
27 BC to
300 AD
Population shifts toward the Middle and Near East, implying an influx of people; ancestry is highly variable between individuals
Late Antiquity
300 to 700 AD
Ancestry shifts back toward northern and central Europe, still highly variable
700-1600 AD
Continued shift toward northern and central Europe, homogenization

Steppes ancestry (= Indo-European invaders) appears much later in Italy than in central Europe, as one would expect, although the data is pretty poor. For me the most striking discoveries come in later periods when the data is actually pretty good. At the height of the empire Romans were genetically much closer to people in the Eastern Mediterranean (Jews, Syrians) than they had been in the Iron Age or would be later. This implies a major influx of people from that region. Then, in the 300-700 period, the population changed to become more like that of Central and Northern Europe, again implying a major influx of people. In both of these periods Romans were highly diverse. After 700 the influx of genes from north of the Alps continued at a lower rate and the population gradually homogenized.

The data is wonderful because it provides real evidence for things one might have expected. During the late Republic the Romans took tens of thousands of slaves in the eastern Mediterranean, and between them and willing migrants enough people moved west to substantially change the Roman population. In the Late Antique period our written records are full of invading European barbarians – Vandals, Goths, Lombards – followed by more waves of invaders like Franks and Normans. These people, too, left their mark. The end result, shown by 50 genomes of the 1700-1900 period, was a population that sits on the scatter plots about half way between Syria and England.

The Eurogenes Blog has a little video that shows you the Roman sample moving around the scatterplot, very clever.

Good popular article at Science Daily.

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