system
Given the following post, respond as if you're commenting on Reddit:
human
Is there any act or practice that is universally condemned by all known human societies?

I was thinking about some of the worst ones, but everything I can think of appears to be tolerated by some aspects of human culture. Killing babies? Carthaginians and Spartans did it regularly. Cannibalism? Common in a variety of ways. Necrophilia maybe? 

If nothing is universally condemned, then can one argue that there is no shared human morality? If there are practices that are universally condemned, then what do you think makes them so, compared to things like killing babies?
gpt
Without any specific data, we can discuss particular topics. Things like necrophilia, incest, rolling around in feces, etc. might be lumped together as prohibited for physical safety reasons. When we examine the daily activity of human societies, we might guess that most human groups establish and maintain the value of human life (or at least some individual human lives). But this is not universal, as can be witnessed by suicide bombers, Andres Breivik, etc. 

So, the answer is, there is no shared human morality. What we share is an existence (though some argue this point) and physical/mental capacities that drive us to create and maintain values with symbols. Morality is a cultural/symbolic construction created by our words, customs, practices, and actions. It is relative to, dependent on, and sourced from this meaning-making.  These meanings become moral standards, which often converge around shared values, like that of human life (which is required for, well, everything). 

Even what makes someone entitled to all the rights of human life can be revoked for moral reasons (think, rights taken away from murderers). These standards are often negotiable and contextual in law. In other systems, there are only absolutes (think, religion). Morality is a way to continue and uphold particular values, thus it becomes necessary to examine what a culture values and then how they work (with moral action) to keep those values.

Thus the question becomes, why do certain societies value particular things in a particular way?