Aliens do not seem to be interested in hybridization, they do not need it. Aliens changed the ancient man to become a container suitable for an extradimensional entity conventionally called "soul" this entity adds its consciousness to that of the body suitable to contain it . the soul attaches itself to the DNA and enters phase with it, like a third electric wire. But if the DNA is not perfect the soul does not hook and she tends to want to go out (it happens with the body of the terrestrial extra). Even human beings are not all compatible, it seems that statistically only 20% is compatible and has the soul. so if this data is correct it becomes the first reason to hide the UFO phenomenon. accepting that there are aliens is possible, but to reveal that only 1 in 5 people has the soul is not possible, it would destroy human society in a few months.