Neolithic coastal megastructures

A newly mapped 120‑m stone wall 9 m underwater off Sein Island shows hunter‑gatherers or early coastal communities in Brittany built large, deliberate seawalls ~7,000 years ago. The structure (TAF1) forces a rethink of how and when prehistoric groups coordinated heavy engineering, likely as rapid responses to post‑glacial sea‑level rise and to protect shoreline settlements. — If replicated elsewhere, these finds rewrite public narratives about prehistoric engineering, provide concrete case studies of ancient climate adaptation, and explain the local roots of submerged‑city legends like Ys.