Human Social Evolution utilizes morals precisely as genes provide the fabric for evolution.
In biologic evolution, genes express themselves as "behavior" that, if "right", allows that population to continue.
If "wrong" that population goes extinct.
(I put parentheses by way of acknowledging that plants don't have "behavior" as humans do, but they too are at the mercy of evolution for their continuing existence! "Behavior" in this case is still about genes expressing themselves and being "selected" or not.)
The same evolutionary mechanism serves to evolve human populations (Nations/societies/ tribes/families).
Groups of humans have a common goal to have the group continue.
Morals are the behaviors, both encouraged and prohibited, that define a society's social contract with individuals.
If people behave according to societal dictates, the goals of the society are supported. If those goals are able to overcome the multitude of "environmental" factors, that society continues and its morals (right behavior) are justifiably credited.
Morals - Culturally relative (no surprise) and Culturally relevant
At the most basic level, we're social primates, and therefore have to get along in groups.
As with language, and learned concurrently, a specific mix of right behaviors provide for the continued existence of a society.
Morals are learned within one's nation/culture/society/tribe/family.
Jews are forbidden pork.
Micronesians celebrate pigs.
Both are acting "morally", and would say the other is acting immorally, or irrationally.