Humans can obtain sufficient vitamin C from consuming animal products, which likely led to the loss of endogenous vitamin C synthesis.

“some 60 million years ago or so the human species entirely lost the ability to synthesize vitamin C in our bodies okay now obviously that started with out with a random mutation that was selected for so we need to take that concept a step further and go well okay it's not just that some people developed or some people developed this change whereby that those particular people can't make vitamin C and and others that made vitamin C continue to live long and happy lives doing that as well the factors no human being none has the ability to synthesize their own environment C that means that gene was not just drifting away it was not out it was selected against there was a good reason why we needed to get rid of that gene to get rid of making the substance”