When my physiotherapist asked me how I sleep, I said “on my stomach”, he was surprised. So it seems that most people sleep on their back (at least in movies). So why does mankind sleep on their back, unlike all other animals, birds, reptiles and even insects ?
My cats sometimes sleep on their backs, but cats is weird.
I sleep on my stomach too FWIW. It means I don’t snore, which is an unusual trait in hairy-assed blokes such as myself. I’m not sure it’s the best position for your back - my back is OK but it does have quite a curve to it. Not sure if I’d call it lordosis, but it’s more curved than most - I’ve wondered if sleeping on my front has anything to do with this. Just thinking about it in simple terms, sleeping on one’s side would appear to be the best bet for spinal health.
We have a newborn and advice in the UK is overwhelmingly to put him to sleep on his back. This is apparently safer, but it seems to me that he would prefer to sleep on his front. I’ve had this confirmed anecdotally by health visitors that babies prefer to sleep on their fronts, but must be put down on their backs nevertheless in this day and age.
I thought most people slept on their side (not that I have a cite, just an idea).
Some WAGs: It’d make sense to sleep on your stomach to protect your abdomen. On the other hand, it’s easier to get up quickly if you’re on your back or side. Also, the massive gluteal muscle would make sleeping on your back more comfy than grating against the ground with your hip bone. This is all assuming that sleeping positions are older than our current society. And I don’t know if that’s the case.
Personally, I just don’t sleep on my stomach because it makes my boobs hurt.
I expected that answer. They do that to amuse you and Youtube viewers. 
I should have said “on their back and side”.
I understand that women would be uncomfortable sleeping face down.
Also, sleeping on one’s back induces snoaring…
put me down as another side sleeper. I actually find it impossible to fall asleep on my back, though I can shift into this position whilst asleep. I know if I do, because I get a swift poke to the ribs from my wife when the snoring starts. Never really tried sleeping on my front.
I am a woman (a well endowed woman, FWIW) and I sleep on my stomach. My boobs don’t get in the way and prevent me from sleeping at all. I know a lot of women sleep on their stomachs…in fact, I remember my mom wondering if they made special pregnancy mattresses with a cut out for a baby-filled tummy so she could still sleep on her stomach when she was pregnant with my little brother.
A definite stomach-sleeper here. Frankly, I have too big a butt to sleep on my back. Even when I was younger and in better shape, my glutes kept my lower back from touching the floor/bed, which does not lend itself to comfortable sleeping. My mother put me down to sleep on my stomach as a babe - that may be where I acquired the habit. Since the spine has two natural curves in it (one at the neck, the other at the lumbar region), thereby creating odd pressure points, I find it hard to believe that “mankind” sleeps on its back.
If this Man Kind of sleeps on his back, he starts snoring. Then his Woman Kind of punches him until he turns onto his side and stops. I don’t necessarily wake up during this.
I do recall a Ripley’s Believe it or Not cartoon that claimed that Man Is THe ONly Animal Who Sleeps On His Back, but Ripley’s less trustworthy than Wikipedia. Our dog and several of our cats (as noted by others above) have been known to sleep on their backs.
I used to sleep on my stomach all the time, but now, I find whenever I try to do that my arms fall asleep.
For you stomach sleepers, how do you position your srms?
I usually sleep either on my back or my stomach–I can’t get comfy for long periods on my side, but then again, I don’t think I ever wake up in the same position I fell asleep in. My husband sleeps on his side mostly, on his stomach never, and on his back until I wake him up (he snores in that position).
Usually I’ll rest them above my head on the pillow. I’m been known to wake up with them under my pillow though (not a good idea, BTW).
No. You might have to make some adjustments, but I normally sleep on my stomach with my right arm under my pillow.
Probably because unlike them we walk upright. Lay us on our stomachs in our natural position without our heads turned and face is in the pillow.
Other mammals can lay on their stomachs facing forward cause that’s how they walk around all day.
Mammals also don’t have ball-socket joints for shoulders so lying on their backs leaves their front feet up in air which can’t be that comfortable.
You might want to protect your abdomen, but then, humans are fairly large, nasty primates that attack and defend with their arms, legs & maybe teeth, and you’d want those available. A lone human sleeping in the woods would likely sleep with his back against something leaving his eyes, arms and legs facing trouble. Sleeping in groups, as we most often probably were, we probably haven’t been easy prey for very many things over the last million years.
Ugh. I haven’t slept on my back in over 15 years, save for a hospital stay. I start to feel nauseated, just like I’m carsick, whenever I try to sleep on my back. It makes me distinctly uncomfortable in every way. When I got my bellybutton pierced, and later when I got my nipples pierced, I was able to sleep on my side, but I definitely don’t prefer it. Square on the tummy is the way for me.
Baby conure parrots often sleep on their backs and freak out new parrot-owners.
I always used to sleep on my stomach, till I started getting lower back spasms. Stomach sleeping is really bad for your back. Now I’m usually on my side, sometimes on my back.
I am sort of skinny-ish (though for some reason my BMI tells me the opposite). My arms fit into the channel between my belly and my groin, so that my hands cup my upper thighs.
I find it very comfortable, in the same way that the foetal-position feels so very right.
Yep, my current conure does this.
I had a lovebird once who preferred sleeping on his back. Scared the hell out of my husband the first few times, when he thought the bird was dead and not snoozing, but we all got used to it.