It's all about what you're used to.

For a year or two I didn't sleep with a pillow, I can't remember why I stopped using one or why I started again. I was still sleeping on a mattress though. I just used my arm as a pillow.

When I'm hiking, I'm sleeping on the ground without a pillow, and I've never had a problem with it.

On the flip side, I always need an inflatable pillow or a pillow section built into my inflatable mattress when I'm camping, otherwise I need to sleep on my backpack or a pile of clothes or something. Can't sleep without a pillow for the life of me.

A few decades back I visited a traditional zulu village museum. In the wattle and daub huts they had thin logs for pillows, somewhat like firewood. Couldn't find an image in a quick web search.

I read somewhere that we might have slept like orangutans [1] do.

[1]: http://l7.alamy.com/zooms/cbd59529ce184feba45db6c513db67f8/a...

I dozed off last night without a pillow and woke up in that position. Probably a "primate thing".

I sleep without a pillow and have for years. It can be done.

I'm in a pillow dilemma right now and have been wondering about this in the back of my mind for weeks - what position do you sleep in?

I prefer the 'savasana' position, I actually find it more confortable without a pillow in this position, I can also be by the sides or any other position, just not for all night long, I found it actually decreased upper back and neck pains after I removed the pillow

I sleep on my side with my head on my arm.

Before going pillowless, I had a buckwheat pillow. It is less cushy and fluffy than standard Western pillows. I believe they are typical in Japan and not hard to find these days. It helped wean me off the giant fluffy Western pillows.

I have respiratory problems. I sleep better without breathing in allergens and dust mites and god knows what from a pillow. Though it did take a bit of time to get used to doing it differently from how I had my whole life.

Lay on your back.

No, lay on your stomach.

No, lay on your right side.

I do all of these things throughout the night!

A pillow could be a pile of softish branches with leaves.

When I camp I have to put my backpack somewhere, may as well be under my head. "naked and alone" TV show is not terribly historically accurate, surely humanoids have always a bag of something or a rolled up something to rest their head on. Alternately my wife can sleep on my arm and with some work to get my arm position right the blood flow is not cut off; theoretically a household of humanoids could sleep in a line, with the unfortunate one on the end being one of those back sleepers. Interesting bonus is if someone wakes up from hearing a tiger approach statistically half the tribe is awakened automatically for free, silently. Interesting problem is one member wants to roll over or use the bathroom at night and everyone is unhappy.