AtD translation: It all has to be dated more closely than it is anyway.

[Mike Jing]

P278.18-27   “I was out there for a year. Too long. After a while it seeps
into you. Somebody else now is writing up the report, career expectations
will be a factor. I’m just one of the hired hands that dug in the dirt,
climbed those red rocks and benches and carried the gear, got infected with
the insanity of the place, and they know enough now not to pay any
attention to hysterical girl graduates. It all has to be dated more closely
than it is anyway. Whoever the people were, they only lasted a few years up
in those cliffs. After that, nobody knows. Maybe they kept going. If they
were the same ones who made the exodus southward from Aztlán and became the
Aztecs, that might have something to do with those human sacrifices the
Aztecs became famous for.”

What does this sentence mean exactly?