Vitamin C synthesis is a clear example. Humans do most of the work then fail at the last step: https://en.wikipedia.org/wiki/Vitamin_C#Evolution_of_animal_synt

Vitamin C synthesis is a clear example. Humans do most of the work then fail at the last step: https://en.wikipedia.org/wiki/Vitamin_C#Evolution_of_animal_synthesis https://en.wikipedia.org/wiki/Vitamin_C#Evolution_of_animal_...