That's such tiny piece of evidence in the face of all the other evidence about the case though.  The skull has human (male) DNA.  It looks like a hydrocephalic skull.  It may have been bound in some way during his life as an attempt at treatment.  The human/alien hybrid hypothesis is really not supported at all, and makes vast assumptions (that aliens exist, that they visited earth, that humans and aliens could interbreed, etc etc).  There's a reason theories like this are outside of the mainstream; if the evidence supported it, I'm sure every anthropologist would cream their pants at the possibility of human/alien hybrids.  The reason they don't believe it is because the evidence just isn't there.