Yes actually. We know full well what humans were like in hunter gatherer tribes, because we still have such tribes living today.

I suggest you meet the Hadza. A living demonstration of how different human beings are depending on the system you place them in. When humans have neither competition with one another nor a lack of material abundance they become something quite different.

Your interpretation of humans as assholes comes from never having known anything other than capitalism. If you lived in a burning building and never knew any different environment you would also believe that it is natural for humans to endlessly cough.

Do give that thread a full watch, and read the last couple posts. It will change your attitude.