system
Given the following post, respond as if you're commenting on Reddit:
human
What is the evolutionary advantage of primates losing endogenous Vitamin C production? And are there nowadays humans who are able to produce their own Vitamin C?

I am wondering because it seems plausible to me that due to illnesses spreading more rapidly in human societies as opposed to hunter gatherers, it could be that the immune system advantage of producing Vitamin C could outperform whatever advantage the loss of Vitamin C production had.
gpt
Evolution does not necessarily have to be an advantage, it can be enough that it is not a disadvantage.

If food supplements the Vitamin C intake, there are no negative consequences of no longer producing it.

If those with the gene variation that no longer produces Vitamin C do not have any disadvantages because of it, the gene can spread. Which is likely what happened.