All eight of the contributor’s answers to “What does evolution tell us about morality?” provide informative and interesting perspectives.
However, none referenced or proposed any specific basis for what I would consider a culturally useful “evolutionary morality." In hopes of provoking discussions about the possibilities for such a morality, I want to informally explore a candidate suggested by consideration of morality’s ultimate source.
The process of evolution itself is certainly not the ultimate source of morality. Evolution is only the process that encodes behaviors in our moral sense and cultural moral codes that increase the benefits of cooperation in groups—the apparent function of morality in human cultures. There is nothing necessarily moral in an absolute sense about these behaviors as is illustrated by the diversity, contradictions, and bizarreness of past and present cultural moral codes.
Game theory has revealed cooperation strategies, such as direct and indirect reciprocity, whose elements appear to be universally encoded in our moral sense and cultural moral codes. But game theory also reveals the cooperation benefits of dividing people into preferred in-groups and ignored, or even exploited, out-groups. There is nothing necessarily moral, again in an absolute sense, about cooperation strategies that exploit out-groups.
But consider the problem these cooperation strategies are solving. Could that problem itself be the ultimate source of morality?
In our physical reality, large benefits of cooperation are commonly available. However, initiating cooperation exposes one to exploitation. Exploitation is virtually always the winning strategy in the short term and can be in the long term. However, exploitation makes cooperation unsustainable. These circumstances set up a cross-species universal cooperation/exploitation dilemma. How can species overcome exploitation’s short term "winning" hand in order to sustainably obtain the large benefits of highly cooperative societies?
Fortunately for us, our ancestors came across reciprocity strategies, such as direct and indirect reciprocity, that solve this dilemma. All such strategies include two elements: motivation to risk initiating cooperation and motivation to punish exploitation, though that punishment may just be public shaming or shunning. Encoding these solutions into our biology and cultural norms enabled us to become the incredibly successful social species we are. Since this cooperation/exploitation dilemma is innate to our physical reality, it defines an ultimate source of morality independent of biology, evolution, and game theory.
Further, there appears to be a cross-species universal subset of strategies that solve the cooperation/exploitation dilemma. These are strategies that exploit no one, that only advocate cooperation and punishment of exploitation.
This cross-species universal subset of strategies defines a candidate universal moral principle: “universally moral behaviors are elements of strategies that overcome the cooperation/exploitation dilemma without exploiting anyone."
But the cooperation/exploitation dilemma is merely a claim about what "is" and the universal subset of strategies that solve it only define universally moral "means." What our ultimate goals somehow "ought" to be is beyond science’s domain. Can we actually define a morality just based on moral "means" without specifying moral "ends?"
For many people, religious and secular alike, their best compact summary of morality is some version of “Do to others as you would have them do to you." No goal is stated. All that is described is moral "means"—it is silent about moral "ends." Knowledgeable Christians should be able tell you that Jesus said this version of the Golden Rule summarizes morality. This is an example of a moral principle that does not have to specify a goal in order to be culturally useful.
This version of the Golden Rule is also highly relevant. It is the best heuristic (imperfect as it is) I am aware of for initiating indirect reciprocity, arguably the most powerful strategy known for overcoming the cooperation/exploitation dilemma. So, if you follow the Golden Rule, you are already following a cross-species universal morality that is inherent to our physical reality.
Why might a group decide to advocate and enforce such an evolutionary morality? While science cannot tell us what we ought to do, science can tell us how we are most likely to achieve our needs and preferences. Many of our needs and preferences can be best met by cooperating with others. Groups could decide to advocate for and enforce such an evolutionary morality because they expect it to best meet their needs and preferences.
Of course, there would still have to be a tremendous amount of philosophical work done to go from the above universally moral "means" claim to the set of moral norms that would define a coherent, well-functioning cultural morality in all its complexity. In any event, the above statement of the principle underlying this candidate “evolutionary morality” might be worth exploring further.