In Fortean theories, the relationships between Greys and other races (such as Reptoids, Andromedans, Lyrans, Pleiadians, etc) is usually more complex, although it is often speculated that the Greys themselves may be both reptilian and/or genetically-engineered in origin. Other sources describe the Greys as "employed" or, according to some sources, enslaved to appear as a researching "workforce" while doing another race's bidding Little is known about Grey social structure or civilization. As mentioned before, its thought that Greys are sentient creatures that act as vessels, or remote bodies - for some other intelligence. When they are not under the direct control of a conscious entity, they seem to behave much like robots. According to witnesses, crash survivors are often found wandering aimlessly around the site. And follow when told to and will stand where you left them if you no longer want them to follow you like "mindless" children. Greys are said to speak to humans telepathically in perfect human language (whatever the case may be), but it's unclear if the speaking entity is actually a Grey consciousness or something else. Many abductees have noted that Greys go about their busywork like robots when they are not interacting with humans. They are diligent and purposeful but seem to lack emotional depth, which is consistent with their expressionless faces. The beings also do not display abstract creativity or art. Their craft design is bland, deliberate and as expressionless as their faces. No abstract design, art or decoration can be seen inside or out. The design philosophy clearly favors high efficiency and function over form. It's been well noted that Greys do not attempt rescue operations for crash survivors, nor do they attempt recovery of craft or its deceased. This lack of concern for lost comrades reinforces the theory that these beings are disposable vessels for something else, which remains a mystery. The overall consensus about the Greys observed behavior is that they are neutral. Neither benevolent nor malevolent. Abductee accounts sometimes describe the creatures speak in a comforting manner while conducting medical examinations. This behavior suggests a level of empathy, the value of which is somewhat diminished by the taking of people against their will and painful medical procedures. They do return them however, usually without serious physical harm. The Greys have been consistently described as short, thin humanoids with grey, hairless skin, and a conspicuously large cranium. Their eyes are large, black and frequently said to be almond-shaped, and their facial features are restricted to a pair of small slits in the place of the nose, and a small, expressionless mouth. Their fingers are usually long and dexterous. Their bodies are proportionally small, and they don't appear to have external genitals. A putrid odor of something like ammonia is often reported by abductees and recovery crews. Greys are exclusively telepathic and do not appear to be capable of producing oral language. The oral cavity contains no teeth or tongue, and the throat contains no vocal cords. Humans in close contact with live Greys frequently report the beings speak to them in their minds. There is minimal technical knowledge about their biology, but we do know a few things. Similar tolerances to heat and cold are observed and cellular respiration requires oxygen, The cardio-vascular system includes a heart, lungs and circulatory system. The lungs do not reciprocate with a diaphragm muscle like in humans but resembles a unidirectional flow system similar to birds. The brain is +20% superior in volume to a similarly sized human, and the cerebral cortex contains more densely compact folds (gyrification). Due to the absence of teeth, tongue and a very simple digestive system - a liquid diet is theorized. Excretion of waste occurs through pores in the skin, which produces the aforementioned ammonia smell. This also explains the lack of body orifices and certain "facilities" aboard their craft. There are four very delicate digits on each of the hands and feet, with the middle being longer in comparison to the others. There are no fingernails. Blood color is brownish, but higher in plasma and copper in comparison to humans.