It's not that mankind "invents" it, as if everyone gathers around a table and talks out what is moral and what isn't, it's that we evolved as social/tribal animals, whereby empathy was evolutionarily advantageous, which is why most of us have an aversion to things like murdering people, hurting others, etc. We see senses of empathy/"morality" even in lab mice.

Yes, it is conceivable/possible that humanity could continue to evolve, and somehow lose our social/tribal instincts, thus no longer naturally find murder to be wrong to do, but I would highly doubt that would ever happen.