what are we supposed to say again when christians ask us where we get our morality?

[Rampant.A.I.]

Why are you talking about empathy in isolation? Why are you ignoring the other genetic traits of reciprocation and a sense of fairness? Why are you equating this directly with breeding success?

Maybe because you do. As you also said...

Societies with deeply flawed rigid moral systems don't survive long term and are replaced. Societies with moral systems that allow development tend to do better.

The theory of biological evolution is about, and only about, reproductive advantage. In terms of evolution, empathy, reciprocation, and fairness have only survival value. For other values, like moral or aesthetic values, people must look elsewhere.

You keep droning on with unsupported assertions that no one but you believes, desperately strawmanning and equivocating, and pretend no one notices.

It's pathetic. Support your assertions or stop talking.