Caves supposedly dug by giant sloths 10,000 years ago in Brazil.

[Hangedman13]

Given the time frame, could we also be seeing other factors in play? Such as water erosion or even humans finding the caves and co-opting them for their use? Heck, I'd even ponder it's because the tunnel the sloth dug was worn down because they dont excavate tunnels to be any larger than they need to fit. The sloths body wearing it down smooth from squeezing through the tunnel.