male nipples are developmental vestiges, the male condition is derived from response to embryonic testosterone, and is a developmental variation from default.
replyearly stage embryos of both sexes are not easily distinguishable by genitalia, they look morphologically similar. later developmental events culminate in morphological rearrangement to male form.
lack of response to testosterone during development results n a curious state of affairs, where a person is genetically male, having x, and y chromosomes, develops according to a female plan. external appearances are female, with loss of secondary sex development in puberty.
Androgen insensitivity syndrome:
https://en.wikipedia.org/wiki/Androgen_insensitivity_syndrom...
Asking “why” questions about our body / evolution often (not always) gives informative answers. As in the example you gave: https://www.scientificamerican.com/article/the-purpose-of-ou...
replyInteresting finding, though it doesn't explain animals with properly-wired retinas: https://en.wikipedia.org/wiki/Cephalopod_eye
reply(Scientific American is throwing up a paywall even though they're only republishing https://theconversation.com/look-your-eyes-are-wired-backwar... At least they link to the original.)
Correct, though interestingly apropos to the discussion is that sex is one of the ways evolution is able to get around local maximums.
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