Why be good?

[dyresand]

What I am asking is: what is the BASIS for objective moral behavior? Where does it come from?

Evolution plain and simple evolution. 

Animals they have morality they always had and always will have a social morality.
http://www.wired.com/2011/12/rat-empathy/

We even have it because we too are truthfully animals as well so there is no difference.
https://news.virginia.edu/content/human-...tudy-shows

Here is the ultimate problem with morals from a god or even a book. The bible was written so long ago it doesn't conform to modern day society. We for the most part don't see slavery,
we don't kill our kids, we don't openly rape in the streets, and sure as hell we don't kill blasphemers and people who mock you and you religion or the non believers I.E. Atheists. 
We are more civilized and sure as hell were not even barbaric anymore for the most part i mean we still have third world countries and the middle east to deal with.