Anonymous asked:

In a theoretical where a human spent their entire life swimming with no or minimal walking, how would that effect it? Like would they just be kind of awkward and not really intrinsically know the motions to do or would their legs not be able to hold their weight? I know swimming uses different muscles and motions from walking but are they that different?

biologyweeps answered:

Well for one the human would probably die at relatively quickly because our skin is really not meant to be put into water for such long periods of time. The water would basically have to be body temperature or we’d cool out. Despite what some people proclaim - I am looking at you, aquatic ape hypothesis - humans aren’t so great at handling water. We don’t have halfway enough fat to properly isolate us and our skin actually… can’t take it all that well.

Like, after prolonged submersion in water our skin just starts… well, dying, and you’ll develop open sores and shortly after infections up to sepsis. That’s not even theoretical, there’s something called ‘immersion foot syndromes’ which are essentially different ways your feet can start rotting off you if you keep them in water, even warm water, all the time (please do not open that link if you’ve got a delicate disposition. stuff’s gross). Now imagine that happened to your entire body. Yeah. 

So, you’d probably die from some terrible sepsis that starts with your skin leaving your body.

But provided that your skin didn’t decide to vacate the premises early on…

Water is as close to continued zero gravity as you can get on our planet. Zero gravity is bad for you. While constantly keeping yourself afloat would probably keep your muscles from atrophying, low gravity results in loss of bone density (something that astronauts actively have to try and fight) meaning that potentially the legs wouldn’t hold them. in fact the bones may break if you lose enough density. 

So yeah, chances are you would just straight up die and even if my some miracle you didn’t you would have a bad time coming out of it. 

[feathery-dreamer]

Don’t newborns have enough fat to insulate them from the cold? Or is that not sufficient to protect from the cool of water, because I know it sucks up much more energy to warm up than air does.

[biologyweeps]

Nope. Newborns can’t thermoregulate superwell which is why you’re supposed to turn them into little marshmellow people in winter. 

I mean it does make sense, considering that inside the womb they’re kept at a cozy, you know, body temperature. They don’t need to heat themselves, they’re surrounded by heating. 

[aiyumedayori]

Okay so, following that line of thought, does that mean if you tried making a more realistic approach when creating a mermaid, she would need to have more fat? Also is it likely that she would need a sort of fat coating her skin or
I mean, what’s the closest thing to a human like skin that could be constantly under water since lots of mermaids are depicted literally just half human???
And then how would that affect her if she spent time out of the water?

[hexcoderose]

I think mermaid skin wouldn’t actually be much like human skin, is the best answer. You could have slim mermaids, but you’d have to be assuming that their internal biology is very different to the average humans’, and more like a fish, so cold-blooded at least (and those wouldn’t be able to leave the water without magic). If you wanted a warm-blooded mermaid, she’d have to be more like a seal, I assume, so with a good layer of fat and probably to having to spend an amount of time outside the water so their bones could take it. (Idk if that’s how seals work exactly? Maybe their bones are just naturally denser? If that’s the case, the mermaid’s would have to be as well?)  

[biologyweeps]

Yeah if you want mammalian mermaids you should be looking either seals or cetaceans. Big cetaceans in part can’t leave water for longer periods of time because the literally weight too much. Beached whales usually die because their internal organs, especially the lungs, simply collapse under their own weight. They can even break their own bones like that. Of course, a smaller mermaid might not have that problem even if you go the cetacean route of ‘All water all the time’ because they have less weight on the base structure.

(if you have deepsea mermaids, another problem is that a lot of fishes down there tend to be more squishy. They can’t take the pressure change well and they usually don’t have a lot of solid bone structure to begin with, so deep sea mermaids even if fish rather than mammal would… probably kinda explode if raised to the surface to quickly, and probably loose a lot of their form even if they don’t. talk about traumatic injury)

But yes ‘cold blodded’ (ectotherm, really) mermaids would need less insulation though you could still get mermaids with at least limited tolerance for dry land. There are plenty of fish who can tolerate time out of the water in different ways (mudskipper mermaids. imagine it) so having a fishy mermaid doesn’t rule it out yet, though of course you won’t get any legs that way.

Additional bit: if you go the mammal route, please decide if the tail is 1) made of tail and therefore spine 2) made of leg. The two don’t move the same way and even if you go with leg-tail, chances are there wouldn’t be knees, because that sort of flex would actually lose you forward momentum. 

But yeah, essentially you gotta decide if leg-tail or tail-tail (and if you do a fishy one, fish tails go vertically not horizontally) and then consider how they can pose because if you do the ‘knee’ bent on a leg-tail, that’s a broken spine right there. 

Generally, assume that the human half is not actually human but just looks that way. If you want a biologically plausible mermaid you sorta need to go more xeno than with a magic mermaid. Magic allows you to handwave the ‘human skin would literally come off’ problem.