Stable population structure in Europe since the Iron Age, despite high mobility

Area of Science:

• Human population genetics
• Ancient DNA analysis
• European prehistory and history

Background:

• Previous ancient DNA studies focused on prehistoric population shifts (14,000-3000 years before present).
• Limited understanding exists regarding population structure changes from the historical period (3000 years before present–present).

Purpose of the Study:

• To investigate European and Mediterranean population dynamics during the historical period using ancient whole genomes.
• To identify patterns of ancestry and mobility in recent human history.

Main Methods:

• Whole genome sequencing of 204 ancient individuals from Europe and the Mediterranean.
• Analysis of genetic ancestry and population structure.

Main Results:

• High inter-individual genetic heterogeneity observed across most sampled regions.
• At least 7% of historical individuals carried uncommon ancestry, indicating cross-Mediterranean contacts.
• Despite observed mobility, overall population structure remained geographically stable, mirroring Western Eurasian geography.

Conclusions:

• Observed dispersal levels, if modeled with standard population genetics, would predict a collapse of population structure.
• Persistent structure suggests a lower effective migration rate than direct dispersal indicates.
• Transient dispersal, potentially driven by improved transportation and Roman Empire policies, likely explains this phenomenon.