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SerifGrey t1_jdmh25z wrote

Reply to comment by _Dnikeb in TIL, the placenta that forms with a fetus isn't created by the mother. It grows from the fertilized egg and some fetuses actually develop outside the uterus attached to the intestines in the body cavity. by darw1nf1sh

Are you saying humans gave birth long ago in our past without a placenta? so how did the baby get the nutrients from the placenta passing through the umbilical cord? I’m confused.

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Dragmire800 t1_jdmkdjf wrote

Not humans, humans always gave birth with a placenta. Millions of years ago, a mammal was infected with a virus that ended up resulting in a structure that became the placenta.

We can look at the non-placental mammals around to deduce how our non-placental ancestor would have spawned offspring. The obvious is egg laying, like almost every animal does today besides placental mammals. We see this in monotremes like the platypus. The other option is to do it like marsupials where offspring is born ridiculously underdeveloped, and spends its early life in a pouch drinking it’s mothers’ milk.

Live birth is observed in some non-mammals, like sharks. Those shark species sustain themselves by eating their siblings while still in the mother

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SerifGrey t1_jdmun8q wrote

Sorry for my dumb question, I should of known it was none humans but I just didn’t think it through, thank you for the information, very interesting.

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Carbon_McCoy t1_jdppuqe wrote

Unborn shark babies eating their unborn shark siblings just to stay alive long enough to be born is one of the most nature-metally things I've ever read.

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2MegaWhats t1_jdprik1 wrote

Baby Shark is darker than the cartoon would lead you to believe

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DeengisKhan t1_jdmkl4y wrote

No humans existed that were non placental, that evolutionary trait developed many species before us, we just still make use of that method of birth in our biology because it works well enough to have kept placental mammals in the game.

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