Much has been made of the fact that both humans and apes need to supplement their diets with vitamin C -- and this fact is used as evidence that we are related to apes. It is much more complicated than that; and there may be an explanation apart from the standard evolutionary one. First of all, this article http://www.grisda.org/origins/12096.htm chronicles something very interesting. Vitamin C is synthsized in different organs in different animals. It can be synthesized in the liver or the kidney. Birds, for instance, synthesize vitamin C primarily in the kidneys. Mammals synthesize it primarily in the liver. I am curious how evolution explains this. Especially since we are -- evolutionarily speaking -- all 'related' to fish, where, if and when vitamin C is synthesized at all, it is synthesized in the kidneys. So here is the evolutionary picture as it seems to be indicated: Vitamin C synthesis does not exist in most fish. Vitamin C synthesis exists differently in most birds than in most mammals. Therefore there must have been -- again evolutionarily speaking -- an ACQUIRING of the ability to synthesize vitamin C in two different ways as fish mutated into other forms of life. And then the ability was selectively dropped in various forms of life. It's not the dropping of an ability that would concern me if I were an evolutionist -- but the acquiring of that ability when it did not first exist. And then to show that it was not even acquired consistently (speaking of where it is synthesized) in 'closely related' animals. Here is a possible alternative take on the thing. We know that mutations occur. We know that if the mutation results in the death or inability to procreate in an organism, that this mutation will spell an end to that particular line. Therefore, it can be said with certainty that if the mutation -- if this is what happened, which I am willing to go with here for the sake of argument -- disabling the synthesizing of vitamin C occurred and the animal and population and species survived, it could only have been because their diets were sufficient not to have minded that mutation. In short, the heavy vitamin C enriched diet came before the disabling of the genetics related to it. Among vertebrates, perhaps, those with the widest and least restricted preferences regarding diets were those who simply never noticed that mutation, whereas others which may have suffered that mutation died (meaning, also, we would not know about the presence of that mutation!). Heavy consumption of fruits and leafy foods would have had to have preceded the loss of vitamin C synthesizing ability, not followed it. If this is the case, there is no need to claim relationship at all among any two groups of organisms on the basis of vitamin C synthesis -- it would be better to look at preferred diets as the cause and not the result of changes in this area.