'Grey' aliens appear like that because they've taken DNA from humans they have abducted, zany Professor David Jacobs claims.
Giving his unusual theory on grey aliens, the professor of history at Temple University specialising in Ufology, claims it all 'boils down' to them having a slit for a mouth.
After highlighting the similarities in appearance between grey aliens and humans, the professor is convinced they've been created from the DNA of people that have been abducted.
Although grey aliens have been popularised through TV shows, movies and within the media, there has never been any scientific evidence to support the existence of them, reports the Daily Star.
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Despite this, the professor has consistently claimed that aliens are walking among us on Earth and are planning for a “full invasion”.
Speaking on the Richard Dolan Show, he's now shared his theory on how alien greys came into existence and he says it all boils down to the slit for a mouth.
He claims that they've been created through DNA from human abductees as every person who claims to have been abducted always talk about grey aliens.
Professor David Jacobs said: "When people say they were abducted, they almost always talk about grey aliens.
“Because we were being abducted, they used a little bit of us in making grey aliens.
"The reason I’m saying that the grey aliens might have human DNA in them is because grey aliens have two huge black eyes."
He went on to explain alien greys have two holes on the sides of their heads for ears which they need to be able to hear.
Furthering his theory, he acknowledged they've been characterised for having two holes for a nose which again, is similar to humans.
However, the anomaly that he mentioned was the fact that they're believed to have a slit for a mouth, which he claimed makes no sense.
He continued: "The question is, why do they have a slit for a mouth? They do not breathe, there’s no evidence for them breathing, and they get very very close to people, sometimes even touching foreheads."
“I’ve asked people, ‘do you feel their breath on your face?’ The answer is always no. They don’t have lungs, they have very thin little bodies, there’s no back and forth of the lungs expanding and contracting."
The professor explained that alien greys don't talk as everything is telepathic and don't eat in the normal way that humans do.
He continued: "So why is that slit for a mouth there? The point is that there’s probably human DNA in those grey aliens… which allowed for the growth of grey aliens.
“I don’t know but that’s my best guess, and it all boils down to the slit for a mouth, which they should not have.”
The professor's theory on how alien greys came into existence comes after an ex-NASA scientist has recently claimed humans will make contact with aliens within the “next handful of years”.
