Cold

Less than a hundred years ago, people would often simply not make it through the winter. I would just be too cold for them and they would die. I assume there are still places in the world where that happens.
It's hard for me to imagine living in situation where my primary concern was simply staying warm and finding food. I don't ever worry that I'm going to die from the elements.
I imagine that the good thing about living in danger of freezing to death is that it keep your priorities ordered. If you can't find firewood, you're probably not going to worry too much what other people think about your hairstyle. The number of real problems a person has is inversely proportional to the number of the problems a person makes up for himself.