>Morality is defined here as that for which we are held accountable by others, when we work together towards joint goals.

You exclude by definition a personal morality, even though you say, finally, that,

>Again, there's always going to be a tension between interpersonal and intrapersonal morality (the conscience and how we treat others, and behave) and cultural morality, which may dictate just the opposite of compassion and justice.

I agree that we live within a historical moment influenced if not hegemonically constrained by value systems, and that this context brings us "head to head" with "cultural mores of the day."

But it is a bit of a stretch to then say our notions of right and wrong are necessarily those of an "in-group." (I am reminded of Wittgenstein's rejection of private language – with which I disagree.) Being cognizant of the rules of others does not rule out one's own; in particular, it does not rule out mutancy – e.g., that of Nietzsche "Most people would not do that" does not deny the exception to the rule, including the exception that may become the rule.

I am not qualified to comment on Michael Tomasello's, or your, evolutionary theories of morality. That said, they don't cause me particular concern. Indeed, without expertise on the matter, I observe behavior in species more distant to us than Homo erectus that I could accept as "moral."

At an even more rudimentary level, I am sympathetic to the observations of Kropotkin and others: inter-species co-operation, or at least constructive co-existence, is commonplace in nature, and, at least possibly, a foundation for morality. In short, we share the evolutionary experience of the ecosphere. Arguably, ecosystemic existence encourages notions of right and wrong that presage the pragmatic needs of our species, moreover the inherent sentience, consciousness, intelligence of such existence has not only a past but a present and a future, and thus a potential for agency.