[Carry_Okie]

At least here, there has to be archaeological evidence (which every site gets checked for before we drill)

LOL Here, "archaeological evidence" is anything 75 years or older.

[Smokin' Joe]

Here, at least, the standard is that the evidence has to be flake debris, tipi rings or some such. (a scattering of beverage containers, cigarette stubs, etc. doesn’t count, unless definite provenance can be established...)