Going the' whole hog' is a descendant of going the whole 'orang utan'

 To go the whole hog is a common expression meaning, generally, going the full mile

’ For Lyell and Darwin; going “the whole orang...utan” was allied to evolutionary thinking and meant, most painfully of all for those of a Religious bent, the term meant linking humans to animal ancestors.

 It meant that humans were not creations separate from the rest of the animal kingdom. To go the 'whole orang utan ' then, meant not just to treat humans scientifically but to go all the way to making them animals like all the rest.