That seems to be a reasonable thought, although incredibly difficult to prove. Primates and guinea pigs both dropped the ability to synthesize Vitamin C, throu

That seems to be a reasonable thought, although incredibly difficult to prove. Primates and guinea pigs both dropped the ability to synthesize Vitamin C, through different mutations. Now both species have to consume it in their diet to survive. Incidentally, the story of the broken Vitamin C gene in primates and guinea pigs is the main argument that gets used to show how the theory of evolution is supported. In all primates, including humans, the gene to make Vitamin C is in our DNA, but mutated so that it is not usable. But all primates have the mutated gene in the same place. Guinea pigs have a different mutation to the gene. The chance that all primates had the mutation in the same location simultaneously is very remote, suggesting all primates shared an ancestor that developed the mutation.