Humans are one of the few mammals unable to manufacture ascorbic acid in their liver. Most other animals, except the ape family and guinea pigs, produce ascorbic acid in the liver from glucose in relatively higher amounts than we receive from today's modern diets.

Good way to cripple or control humans is to make them weaker and defective. Most species that dont create their own vitamin c are those like the fruit bat (eats a lot of vitamin c from fruits)