I submit the following for your study.  This was supposedly an impression of an alien bodies mandible taken from Wright-Patterson Air Force Base.  I have long surmised the so called “grays” are our distant descendants from a time in the distant future where our Sun has aged, turned red, expanded, and boiled most of the surface water off the planet.  Here are some of my reasons:

• They abduct along family lines.  They only abduct certain families, maybe 1-in-100.  The reason I believe this is so is because these are the families whose genetic lines survive until that time and so they are only interested in them.
• They are adapted for darker environment that would exist in the distant future because more of the Suns output has shifted into the Infrared.  Even though the total solar flux is greater at that time, it peaks in the infrared and not the visible so it is less in the visible spectrum.  So the need for the big black eyes, more efficient at light gathering at the expense of other capabilities.
• Their skin is gray, no pigments notably active at any light frequency within the visible range of approximately 450nm-680nm because solar output is low in this region at that time, instead it peaks somewhere nearer 1000nm.
• And now this mandible adds fuel to my argument because it is shaped unlike any primate that currently exists BUT it has exactly the same number and types of teeth as do modern humans.
• A creation of a hybrid species, something that seems tops on the grays agenda, would only be possible with biologically compatible beings, which our descendants would be up to a point.