A part of physically derived behaviour is 'spiritual' behaviour. In theory it can be traced back to an interplay between internal systems, but it still has an 'otherworldly' quality nonetheless.
What do you mean by spiritual and otherworldly?
I think if you take a closer look at my post you'll see that the answer is already in there.
I get that if you analyze most forms of human behavior it can be reduced to some form of evolutionary fitness yadda yadda. But I genuinely believe that there are many of us who actually want to help others, or make the world a more beautiful place, without any expectation of reward or gain. People who want to transcend the limitations of human nature and society, to 'go beyond' as it were.
That's certainly not everyone. But I think it's true that our cultures aren't entirely about cold rationalism and efficiency, they're also about beauty, friendship, love, sharing, etc etc. Really you can call that whatever you want, spirituality or otherwise, but when you break it down human experience feels like more than the sum of it's parts. Like there is something
more there than pure survival.
And that's why so many of us have come to believe in a literal soul, and that humans are somewhat God-like. Because immediate perception suggests that this is the case. What I'm suggesting is that this perception isn't exactly wrong, it's just an incorrect interpretation of the source of the perception.
It's natural selection in a social species with hugely complex endocrine interactions that are outside, but both driven by, and drivers of, neural processes.
If you want your genes to propagate through the population, it's not enough to understand that you made an error; You need to also feel bad about it, perhaps guilty about it.
It's not enough to notice that that person is sexually attractive, because you will be outcompeted for their attention by someone who both notices
and falls madly in love.
It's not enough to understand that it's better for your kids if you do X, Y, or Z; to be competitive, you need to be irrationally passionate about their success.
Of course, we all know of situations that get very ugly due to people overdoing these emotional states (and millions of others). But underdoing them isn't evolutionarily successful, or at least, wasn't for most of social primate evolution.
None of this is a mystery - but most people are unaware of it, and prefer to think that it's some kind of external influence (which from a purely neurological perspective, our brains are correct to assess that it is).
Our brains and their workings are constantly subjected to external influences that are entirely driven by a desire for us to succeed as individuals. But those influences, despite being external to the brain, are not external to our bodies. They are our endocrine systems, and while it is fashionable to pretend that civilised people are now risen above such base influences, they are nevertheless a massive driver of our behaviour - perhaps even more important than our brains.
Your brain constantly claims to be in complete control. But brains are lying bastards, and you shouldn't trust yours, particularly when it's big-noting itself.