 It has been argued that knuckle-walking of chimpanzees and gorillas  originally started from fist-walking as found in orangutans.
<meaning-changed>  It has been argued that knuckle-walking of chimpanzees and gorillas  originally started from fist-walking as found in orangutans.
 It has been argued that knuckle-walking of chimpanzees and gorillas , arguably, originally started from fist-walking as found in orangutans.