Charlie Stross8000 year old fortifications discovered in Siberia (appears to predate agriculture in that location): https://phys.org/news/2023-12-oldest-fortresses-world.html
Oldest fortresses in the world discovered
In a groundbreaking archaeological discovery, an international team led by archaeologists from Freie Universität Berlin has uncovered fortified prehistoric settlements in a remote region of Siberia. The results of their research reveal that hunter–gatherers in Siberia constructed complex defense structures around their settlements 8,000 years ago.
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