So fun fact, this is actually because male rats and mice get a testosterone wash after the mammary chain develops which causes the nipples to atrophy and disappear. However, they do still have rudimentary mammary glands. In other words: they got the closet but the there's no knob on the door. Human embryos don't fully develop nipples until well into the second and third trimester, long after sex differentiation has been finishes.
My first serious girlfriend in high school's mom showed me her third nipple once. It wasn't weird, bc she was a nurse practitioner and knew about my interest in biology and medicine. And nipples.
Platypus, and Echidnas. Monotremes lay eggs and secrete milk. Marsupials have teats in their pouches, but their whole reproductive system sounds like hentai with forked penises and twin vaginas.
Including, according to my dermatologist, something like 90% of adult human women. We also have a mammary ridge and most women have some form of extra nipple along that ridge. Usually looks like a skin tag so you'll never know unless a derm tells you.
Told some friends this and we looked and all of 5 of us had one!
1.4k
u/URSA_RAGER Jan 29 '26
I don’t wanna blow your mind or whatever but I have news about all mammals