aliens are biologically different from humans.
Anthropomorphic thinking, however, lies close to the surface of speculation about extraterrestrial intelligence. SETI pioneer Frank Drake was once asked what form an intelligent alien might assume. He answered:
"They won’t be too much different from us. What I usually say, when people ask me that question, is that a large fraction will have such an anatomy that if you saw them from a distance of a hundred yards in the twilight you might think they were human."
Drake continued his description by noting that it was advantageous to walk upright on two legs with your head on top, eyes near the brain, and mouth near the eyes. He clearly believed that human anatomy serves as a pattern for intelligent aliens. Well, old Gorn on the left won't complain! When Drake was asked if aliens were real, he candidly responded: “You talk about something enough times, you begin to believe it. And we sure talk about this a lot.” Since the seventeenth century, philosophers and scientists have understood that anthropomorphic thinking exists in science. That is why scientists differentiate fact from value, resist granting humans a unique status in the universe, and avoid searching for purpose in the cosmos. Scientists claim they can produce objective knowledge even though their work rests upon human perception and understanding of the physical world. Sagan had his own solution to the problems introduced by anthropomorphism. He asked scientists to reject the chauvinisms that marred their thinking. A chauvinism is simpler to overcome than entrenched anthropomorphic thought because the former is easier to recognize and vulnerable to rational argument.
The main chauvinism that threatens the study of extraterrestrial organisms is the widespread belief that life must have the same physical basis everywhere in the universe. Sagan identified oxygen, carbon, ultraviolet light, and temperature chauvinisms. Each of these rests upon the false assumption that terrestrial and alien life have identical chemical and physical requirements.
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