So, how about this:
Some 336 meters into the cave, the caver stumbled across something extraordinary—a vast chamber where several stalagmites had been deliberately broken. Most of the 400 pieces had been arranged into two rings—a large one between 4 and 7 metres across, and a smaller one just 2 metres wide. Others had been propped up against these donuts. Yet others had been stacked into four piles. Traces of fire were everywhere, and there was a mass of burnt bones. …
Picture at the link.
After drilling into the stalagmites and pulling out cylinders of rock, the team could see an obvious transition between two layers. On one side were old minerals that were part of the original stalagmites; on the other were newer layers that had been laid down after the fragments were broken off by the cave’s former users. By measuring uranium levels on either side of the divide, the team could accurately tell when each stalagmite had been snapped off for construction.
Their date? 176,500 years ago, give or take a few millennia.
Therefore, this was the work of Neanderthals, not modern humans.
What remnants of modern life do you suppose will still be around in 175,000 years or so?