Other people cause the complexity; that's what I think.
Of course. It's population that causes
competition that causes complexity.
When it was only a few dozen people in a tribe, like was pretty simple.
Yes it simple for some things, but there is other things that need to be done in bigger groups. But time that you refer is long gone.
Agreed, population causes complexity by acting like big tribe(competitive behavior). Competition grow exponentially when applying to all humanity.
That is why we need to find better collaborative way of humanity evolution.