 It has been argued that knuckle-walking of chimpanzees and gorillas  originally started from fist-walking as found in orangutans.
<clarity>  It has been argued that knuckle-walking of chimpanzees and gorillas  originally started from fist-walking as found in orangutans.
 Knuckle-walking of chimpanzees and gorillas originally started from fist-walking as found in orangutans.