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I agree that the there is a biological basis to morality, but that doesn't explain everything about it. Empathy is seen in other species and primates are known to have a sense of "fairness." But the full concept of "morality" is a product of our big brains and ability to reason and abstract. I have no reason to think it is entirely based in biology and nothing else. The babies discussed in the link you posted shows only the rudimentary circuitry that lies at the foundation of our morality. As an adult, love and fairness are the key to our moral intuitions. I still have no reason to think that morality is based on a set of rules.
All the best,