What is human nature?

This question has been answered on different plains and many ways e.g. the terms 'homo ludens', 'homo oeconomicus' etc. are attempts to grasp what is human nature. My assumption is: human being is the only one who is able to construct paradoxes an to behave paradoxically. I don’t want to point in the direction of mankind (“We are poluting air although we know it is killing”). I’m talking about really specific actions and stances: Someone is eating although he is full. Someone kills a beloved person. Someone wants to scream nevertheless he keeps silent. Love-hate is another good example to illustrate the idea. Perhaps we could consider this idea without recurring to a simplyfying rational choice-concept or could or nullifying neuropsychological or biological approaches.

I believe that human nature is to question the world around them and seek answers to those questions.