I'm also in favor of mermaids with their tits out.... but are mermaids mammals? Do they have tits at all? If so, do they have conventional human breast tissue and nipples or would they resemble other marine mammals? I'm sure this has been extensively discussed somewhere else on the Internet but I'm not gonna look it up because I'm only interested in your take right now.
Oh now THIS is the kind of thing I want to think about. I loveeeee being able to connect my academic interests with my personal ones! (This is why I've been making so many random posts about things like animals and genetics in the ATLAverse lately. I'm quite lucky to be able to study something I genuinely enjoy learning about!)
Anyway, this is so interesting to me. Because the typical "concept" of a mermaid is someone who is half human/half fish. Which does in fact beg the question: where exactly would mermaids be categorized if they were real?
I can actually accept both arguments, honestly. Mermaids being fish makes sense, as the typical mermaid has both scales and can breathe underwater, usually assumed to be with gills. While mermaids are usually only half-scaled from the waist down and otherwise have skin, it could be that the "non-scaled" half is closer to that of sharks. Sharks do still have scales, but their scales are incredibly small and to the naked eye basically appear to be skin. If mermaids are fish, then perhaps the part that is "human-like" is actually just covered in itty-bitty scales.
However, this still leaves the main question unanswered.
Mermaid tits. What's up with that?
If mermaids are fish, they have no need for breasts or breast tissue, because fish don't make milk. If this were a case of convergent evolution, where mermaids and humans just happened to look similar, they still would be unlikely to develop breasts in the way that humans and other mammals did. If they aren't feeding their young milk, then there would be no reason to develop breasts, and all mermaids would have flat chests (and likely no nipples, either). Perhaps they would develop structures resembling breasts made out of fat or blubber, for insulation and nutrient storage similar to camel humps. Again, this would mean that all mermaids (or all healthy mermaids) would have breasts, and again, there would be no need for nipples.
So that's a strike against mermaids being fish (though again, I could still see it).
What about mermaids as mammals?
To me, this makes the most sense. While they may look half-fish, they are actually entirely mammal.
Or. I guess still technically a fish. All vertebrates are really just extremely evolved and specialized fish.
It's easy enough to account for the scales that the typical mermaid has. (Though I really love versions of mermaids that are half aquatic mammal, like seal or whale!). There are in fact mammals with scales. Pangolins! Their scales are just highly specialized hairs that turn into strong, flexible scales. Mermaid scales could be the same thing. The gills are also easy enough to explain if you want mermaids to have them rather than needing to surface to breathe. Gills are the ancestral trait of all vertebrate animals. They wouldn't have to evolve gills, but rather they would have to just never evolve lungs. Or they could have both, and be a bit more like amphibians.
Being mammals, this would also mean that mermaids could have their tits out. Because as mammals, they'd actually have them.
Something that's easy to notice when you look at aquatic animals, mammal or not, is that they all favor similar shapes. They are made to move as smoothly through the water as possible. To do this, they want to reduce drag as much as possible. The best way to do this is to reduce external structures as much as possible, to let the water seamlessly flow over and around their body.
And. Uh. As someone who breasts rather boobily myself, I can definitely say that they get in the way plenty 😂
Which is why most aquatic mammals don't really develop any kind of external breast tissue. Not the way that many land mammals do, and certainly not the way that humans do! Some have teats that are covered or concealed in some way (most cetaceans), fully inverted (some species of seals) or located externally in an area that already creates some drag (manatees have teats located just behind their front flippers).
So, if mermaids did have nipples located in the same area humans do, similar to manatees -- rather than on their stomachs or near the base of their tails -- they likely wouldn't develop much external breast tissue. They'd be flat-chested, or with very small breasts.
However, there is still a way we can realistically (I say, talking about mermaids) have our mermaids breast boobily through the water!
Breast tissue does not go away on its own. Once it's there, the only way to get rid of it is by surgical removal. This is even true for non-human mammals. For example, you can usually tell if a dog has had a litter of puppies before, because they will often have noticeable tissue development around their teats, even after the puppies are weaned. If mermaids developed breast tissue to nurse their young, the breasts would remain even after they stopped nursing.
So you can have mermaid tits! But only on the condition that they've had a baby in the past.
And after thinking through all of this, I actually... don't know if mermaids would have their tits out...
Not in a seashell bra way, of course. But as I said before, having external nipples and breast tissue can create drag in the water, significantly slowing down movement and speed. It would be pretty damn inconvenient if you had to give up essential speed in order to nurse a baby.
Think of professional swimmers. They don't wear baggy swim trunks or stringy two-pieces. They are aiming to reduce drag in the water by making their bodies as streamlined as possible, so they wear swimsuits that hold everything tight to their body.
So if mermaids did in fact develop enough breast tissue that it could be an issue for swimming speed, they would probably do their best to negate that effect as much as possible.
Mermaid binders is what I'm saying.
That is, of course, assuming they have human-like intelligence. If they didn't, they probably wouldn't develop any kind of breasts in the first place, as without the ability to reduce the drag natural selection simply wouldn't favor it.
So, here's my current proposal:
Mermaids are mammals. Mermaids feed their young via milk. Mermaids do not develop breast tissue during puberty the way humans do, but only develop it as a response to pregnancy. Mermaids who have developed breasts wear some type of clothing to bind them close to their chests so they don't slow their swimming.
However! If mermaids don't have the same type of cultural weirdness around breasts that some human cultures do, there's no reason for them to bind their breasts all the time. They'd need to unbind for nursing at the very least, but there's nothing to say they wouldn't unbind for other reasons as well. If they know they'll be doing a lot of swimming, they wrap them up. But if they're going to be taking it slow or staying in one place for a while, they can let 'em hang. In that way, the clothing they use to bind would be more like "work clothes" than an everyday thing.
And again. No seashell bras.
Honestly, thank you so much for sending this ask! This was so much fun to think about and work through. Who knew mermaid tits could provide so much entertainment 😂
