In the end we are animals, and among many things that means we inherit a bundle of instincts evolved over the ages to enhance survival of our genes into the next generation.  This is not a moral force, nor is it immoral.  It just is what it is, and sometimes it leads to great deeds and sometimes not so great.

For the most part we are not conscious of this.  The instincts work mainly through our emotions -- desires and revulsions, likes and dislikes, wishes and fears, and so on.  Learning to identify them and then step outside them is I think a modern interpretation of the Buddha's insight.