Is there a point in losing the ability to produce Vitamin C?

Cassie-Fooky has decided to usurp a topic better suited for Cassandra or Amelia, but has seen the chance to get in three memes, so the heck with it. The point is, every primate except for lemures has lost the ability to synthesize vitamin C, together with bats and, for some unfathomable reason, guinea pigs and capybaras. While memeing center, left and right, Cassie-fooky presents evidence from scientists, which falls in two groups: some think the mutation happened and, because it did not kill the species involved, well tehy kept going on. Others think that evolution has to have a plan and that there has to be a reason for the mutation to happen. Cassie-Fooky muses for a bit about what Cassandra and Amelia would make of it, and then memes some more.

Resources.

Article on vitamin C
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145266/

Article on why not producing vitamin C may be an idea.
https://www.nature.com/scitable/topicpage/the-mystery-of-vitamin-c-14167861/

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