Science cannot speak to general morality, as an abstract set of axiomatically good values, because it tends to tell us that those are completely arbitrary.

But science also teaches us that humans have a set of common, shared values, and while they may be arbitrary in general, they're not arbitrary to us. And they're shared, because humans are not isolated minds, each coming to existence ex nihilo, but in fact are connected through the process of reproduction. All of us have brain architecture we've inherited from a common ancestor.

This is how science can point us where to look for some practical morality.