/sci/ - Science & Math

>>6120881
nipples don't fossilize.
they're inferred from extant analogs and speculative evolutionary trees.

>>6120889
Thanks Captain Obvious, I was looking for a little more though.

>>6120898
you're welcome.

I could give you what you want, but I just woke up and don't feel like writing that much.

just rest assured that your 'missing link' hasn't been found and won't be.

nipples came from sweat glands.

there is no evidence of nipples in ancient animals.

the earliest nipple is probably something like mammoth udders 30,000 y.a., which is essentially yesterday, geologically speaking.

platypus produce milk but don't have nipples. They extrude the milk through the pores in their skin that covers their milk glands.

Well, this is a somewhat iffy topic since mammaries don't fossilize well at all and well documented science is something that's only existed a few hundred years (an insignificant speck of time from an evolutionary standpoint), so looking back very far is impossible, but from looking at currently living species we can take a few wild guesses.

A common guess is that mammary glands are derived from sweat glands. Looking around there might've been a few ways this could've developed. One is looking at marsupials. They have their mammary glands in their pouches. Monotremes in particular are interesting since they have cloacae and lay eggs.
With those two in mind I point out that some fish secrete "milk" that they spray onto their eggs for nourishment. One guess then is that the milk was once used to nourish eggs or strengthen the shell, keep it moist and clean.

Still, I didn't really draw any conclusions simply because there aren't really any reliable ones. Science just doesn't know yet.

>>6120913
Sweat glands you say? So there were reptiles that used to sweat?

>>6120935
Thank you, this is good stuff.

>>6120889

>nipples don't fossilize

>>6120955
This is not strictly true though, there are some (albeit exceedingly rare), examples of fossilized skins, no nipples as of yet but I live in hope of the discovery of a large therapod with magnificent breasts..

>>6120946
well, technically...

there's no such thing as a reptile anymore, modern phylogenetics got rid of the word.
and no,
anything that sweats isn't a reptile.
so by the time sweat glands appeared the animals having them were essentially already mammals.

sweat glands are like nipples though- they don't fucking fossilize.

>>6120981
there are however no fossilized mammal skins from the Mesozoic or earlier.

in fact most ancient mammals are known from the dentary only.

so not only did their skin not fossilize, the vast majority of their body didn't fossilize.

>>6120988
So, is the common view that nipples evolved primarily in mammals?

I did this mock-up, it's maybe where we came from?

>>6121013
nipples are the one thing that makes a mammal a mammal.

solely because all other animals lack them.

so yes.
nipples evolved exclusively in mammals.

oh shit, you're just fucking with me.
I'm too autistic to notice.

>>6120982
>there's no such thing as a reptile anymore, modern phylogenetics got rid of the word.
I hadn't heard this. What are the replacement categories?