Overview
A humanoid (; from English human and -oid "resembling") is a non-human entity with human form or characteristics. The earliest recorded use of the term, in 1870, referred to indigenous peoples in areas colonized by Europeans. By the 20th century, the term came to describe fossils which were morphologically similar, but not identical, to those of the human skeleton.
Although this usage was common in the sciences for much of the 20th century, it is now considered rare. More generally, the term can refer to anything with distinctly human characteristics or adaptations, such as possessing opposable anterior forelimb-appendages (i.e. thumbs), visible spectrum-binocular vision (i.e. having two eyes), or biomechanic plantigrade-bipedalism (i.e. the ability to walk on heels and metatarsals in an upright position). Humanoids may also include human-animal hybrids (where each cell has partly human and partly animal genetic contents) and human-animal chimeras (where some cells are human and some cells are animal in origin). Science fiction media frequently present sentient extraterrestrial lifeforms as humanoid as a byproduct of convergent evolution.
In theoretical convergent evolution
Although there are no known humanoid species outside the genus Homo, the theory of convergent evolution speculates that different species may evolve similar traits, and in the case of a humanoid these traits may include intelligence and bipedalism and other humanoid skeletal changes, as a result of similar evolutionary pressures. American psychologist and Dinosaur intelligence theorist Harry Jerison suggested the possibility of sapient dinosaurs. In a 1978 presentation at the American Psychological Association, he speculated that dromiceiomimus could have evolved into a highly intelligent species like human beings. In his book, Wonderful Life, Stephen Jay Gould argues if the tape of life were re-wound and played back, life would have taken a very different course. Simon Conway Morris counters this argument, arguing that convergence is a dominant force in evolution and that since the same environmental and physical constraints act on all life, there is an "optimum" body plan that life will inevitably evolve toward, with evolution bound to stumble upon intelligence, a trait of primates, crows, and dolphins, at some point.
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