Stalagmites constructions discovered deep in the Bruniquel Cave (southwestern France) may be the earliest human design projects ever discovered. Dated as old as 175,000 years, they may also be the work of Neanderthals, thus challenging our identity as Homo sapience.

"Neanderthals built mysterious cave structures 175,000 years ago" - good starting read about this story ‎- pa rum pum pum pum
The concept of species is flawed. So why is it so important to us? - a more 'philosophical' (at least Big Picture) take in the story ‎- pa rum pum pum pum
The last picture is from a short movie made by CNRS, 'Cave Structures Shed New Light on Neanderthals', with a good vislalization of the method of dating ‎- pa rum pum pum pum