Most people consider themselves as theists, atheists or agnostics but they don't realize that they are fundamentally humanist because they have not been exposed to situations which would reveal the fact that they are realists and humanists. Here's a hypothetical situation that might expose the truth.
Imagine that gods existed and they have decided to build a new intergalactical shopping mall where Earth is currently located and they are in the process of destroying earth with "nuclear like" explosion. Will you stand up to the gods and tell them that they are wrong and fight for the survival of the planet ? If the answer is "Yes, I will fight for the survival of Earth" then you are a Humanist because you not only disobeyed gods but you derive your decision making process from something outside of gods' will. Your decision making does not depend on existence or non-existence of god unlike atheists who might change their course of action once they are convinced that god exists.
According to The International Humanist and Ethical Union (IHEU)
Humanism is a democratic and ethical life stance, which affirms that human beings have the right and responsibility to give meaning and shape to their own lives. It stands for the building of a more humane society through an ethic based on human and other natural values in the spirit of reason and free inquiry through human capabilities. It is not theistic, and it does not accept supernatural views of reality.
So almost all humans are Humanists ?