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The Artyom Reader points to some articles and a video about a family in Turkey that walks on all fours and communicates using a "primitive language."
Link“The patients had a rather primitive language… they spoke to each other using their own language, using only a few hundred words” which the parents could partly understand, Tan wrote. “They were mentally retarded; they could not count from one to ten. They were not aware of time and space. For instance, they did not know where they live (which country, which village, which city). They were unaware of year, season, day, and time. Otherwise, they had quite strong legs and arms.” “The sitting posture was rather similar to an ape,” Tan added. “They could not hold their heads upright; the heads were flexed forward with their skulls. They could not raise their heads to look forward. This head posture with flexed skull was rather similar to the head posture of our closest relatives, like chimpanzees.”