Oh us humans, definitely.
And we have to dehumanise the 'other' to justify killing them. Because we need their land, or for whatever reason.
The settlers in America, Africa etc, excluded the 'natives' from the need to treat them as human? The law for 'people' did not include natives.
We have to dehumanise the 'enemy' -- which perhaps carries your point that a regard for human life IS an unbuilt human quality?
That's the nature of us animals ... That's why we need God for us not to be beasts.
Demagogues create and/or inflame a sense of insecurity among the populace and tell them who is to blame. Tribal mentality is so deeply rooted in group animals that it's easy to draw out the "us v. them" mentality from us since many would follow this concept 'instinctively'. This is the animalistic instinct I described in my earlier post, and I'd have to say this is actually 'natural' for any group animals including humans to ensure their own survival and prosperity.
So when Jesus said "Love your enemies", this was unbelievably abnormal especially then, when tribalism was a common practice. He is telling us not to be ruled by group mentality, iow, he's telling us to
go against our animalistic instinct that's built in us to help us survive.
Some may say, "Well, if we love our enemies, they'd love us back" ... Well that's a possibility, but what are the chances of that compared to they'd just kill you anyway? Why take that kind of chance? Why is that necessary when your group is stronger than the other groups? Defeating enemies before they might defeat us would be a better bet, that's what animalistic instinct would tell us.
Further, the even more staggeringly amazing 'earthshaking'(yes literally, the Bible says so

) thing is that Jesus actually showed compassion for the Roman soldiers when they were killing him. He asked those soldiers to be forgiven. This was the most staggering thing I have ever come across; this does not make any sense 'biologically', AT ALL.
How can this mindset come from "the survival of the fittest", that you care about the welfare of your killer when you're dying at his hand? How does a person develop this kind of unbelievable (and some would say misplaced) compassion based on natural selection? I have to believe this is something so faaaaar 'supreme' (or you could say 'strange' also) than any animal would ever develop on their own. So, after a long struggle in my head, I finally concluded that Jesus was not of this world.