Tunels are 100 millions year old. We split from chimps 5 millions years ago.
Modern humans are .11 million year old, and we arrived to America .015 million years ago.
the sandstone formation is 100 million years old, not the tunnels
No, what is 100 million years old is the rock layer. The tunnels are `recent`.
Just in time to kill the giants sloths?
as is often the case, one species will make a burro only to have other species take over and modify it, with choice locations, used contiously for several millenia, so an odd scratch here and one there adds up, and we have no other behavioral evidence for this last mega fauna, so who knows?
might find more of these in different stages, with perhaps fossil evidence