When you don't believe in God, you can't count on Him, so you have to rely on yourself and take full responsability.
Atheists are definitely not more selfish or less sociable or less family loving and caring than believers. Nobody wants to be punished and even more, nobody wants to do to others what he doesn't want them to do to him.
Plenty of behaviors the Bible condones are today repulsive ; That's because we evolve as a society and that also shows God has nothing to do with the way we behave.
We know an american family that is very religious and the daughter is alcoholic with all kinds of social and health problems. She has 6 children and can't take care of them.