To apply Arthur C. Clarke s concept on a biological level, any sufficiently advanced species would be assumed to be alien. In the past half-century human beings have increasingly reported contact with extremely strange beings bearing advanced technologies, often with sinister intentions. In this report we will examine the common characteristics of the grey aliens in comparison to humans, possible evolutionary origin scenarios for the grey-type beings, cultural differences and similarities to human beings, and astronomical inferences for the possibility of advanced life on extrasolar planets. This is an introductory report from an exobiological perspective .
Skin color tends to be very light, from bluish-grey to white.
They are generally between 3.5 feet and 4.5 feet tall, have skin colors ranging from pasty white to dark grey, very large brain capacity for body size, thin skeletal structure, small mouth, nose and ear holes, generally reported to have 4 fingers. Encounters with this type of grey can be disconcerting to the human, as they are often associated with intrusive activities. These small greys have been reported to have 4 to 6 fingers. They are reported to be able to subdue the will of the human and induce a kind of hypnosis. A disorienting aspect of encounters with the greys is their silent presence, as physical speech is absent.