Upper Paleolithic 'Greeks' built walls against cold

Some 23,000 years ago Europe was plunging into the Last Glacial Maximum and, of course, it was cold, very cold. Even in sunny Greece, it seems.

So the inhabitants of a Thessalian cave, near the town of Kalambaka, invented masonry and built the first wall ever, not to protect them from any fleshed threat but from a much more insidious enemy: cold.

From Yahoo News, via Archaeology in Europe.