The following series of photos clearly compares the typical features of the human and extraterrestrial (hybrid) skulls.

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The human skull has three basic cranial plates. The alien skull only two.

Especially on the back of the skull, there are two small holes in the alien's skull, which apparently served the nerve endings outside the skull. There are cases where there is one large hole (about 2 cm) halfway between the forehead and the top of the alien's skull.

Skulls that were subsequently shaped as children do not have any such holes.

In people who have had a head bandage in childhood, a straight skull wall of the frontal skull is typically seen. This alien bone is rounded.

If both skulls compare, then the shape and volume of the skull is clearly different.