Separating the wheat from the chaff (or removing the signal from the noise)

This is from my Google UFO notification mail:

http://zeenews.india.com/science/did-aliens-visit-us-in-the-past-artifacts-unearthed-in-mexico-is-a-sign-claim-theorists-watch-2076769.html

It purports to show "ancient" artifacts showing alien (ET) representations created by Mexican cultures from their contact with extraterrestrial visitors.

Most are obvious fakes but a few seem to be representative of early MesoAmerican art (sculpted pieces).

How can ufology or science determine the truth of anything so long as hoaxers and miscreants introduce faked material into the archaeological/cultural sediment?

RR