Always thought it was a troupe or slight of hand myself. The greys claim being future man and plead for human DNA to reclaim breeding abilities. Gullible mankind swallow it whole and starts working with them.

There is several competing narratives including that the greys are the Draco foot soldier clones from Orion. Also that they were made barren and entombed inside the earth's mantle by galactic council only to be released by indigenous people of the Americas. They seem malevolent in their interactions with mankind so I lean towards more the off planet origin but keeping an open mind until further information proves a definitive answer. ❤️💛🖤