second 5 million is to recent, If there had been a HS equalivent that recent there would be evidence all around us.
I used 50 Million years ago for my Avian sapiens TL, and even at that I had the remains of their Civilazation, still exant.
Roads, Mountian cuts, Nano machines, Etc.
Actually the only parts of a civilization left after that long would be stuff they've carved into geologically stable areas and any large deposits of non-reactive metals, like gold.
Without active preservation and maintenance no parts of civilization are going to be around after 10,000 years, hell it only takes a century for roads to be destroyed in most places.
Their could have been a civilization that came close to or met our own level of advancement 30,000 years ago and we'd never know about it unless they put alot of effort into trying to preserve their history by creating stuff that would last in the long term with no maintenance.