In this case I would actually argue that paleoanthropology and comparative animal behavior studies are FAR MORE valuable evidence.
No, I'm pretty sure neolithic man was just as uncomfortable with senseless murder of other people as we are today. They may not have had codification or explanation of why but I doubt their moral inclinations were dramatically different.
Even the ancient Israelites knew (were literally TOLD by God) that murder (the killing of an innocent) was wrong. But the books of the BIble that FOLLOW Exodus are drenched in blood. Blood at the hands of these people who were favored by God and who had direct connection to him. But who could blame them? God himself seems to have encouraged and supported the vicious genocides His followers undertook.
And that all remains in the BIBLE to this day and is NOT dealt with by the morality of most Christians. Ask a Christian how to explain 1 Sam 15:3 and see what kind of answer you get. It's usually a mass of special pleading to get the Israelites (and God) off the hook for a genocide. In fact the story goes on to say that since Saul FAILED to complete the genocide, God himself turned away from Saul.
Of course no Christian today would support a genocide, but then, neither did the Israelites per the Ten Commandments. But they still did it. (this is assuming the BIble is accurate correct in 1Sam and the other books of the Pentateuch regarding the God-ordained land grab.