Bitch modern humans have been on this earth for six hundred thousand years creating an enormous number of distinct and unique cultures which shape the people living under them. The absolute arrogance to think you can generalize a hundred billion people's worth of experience based on what you've experienced in your one tiny lifetime. Humans are so fucking diverse there is VERY little you can say is "human nature." But no please tell me more about how people are just selfish by default despite all the fucking evidence to the contrary.
There may well be a fundamental human nature, but no way to test it. But even past that, the amount of times I can find a counter example to what capitalists call human nature is like I'm an anthropologist dunking on Freud.
also the lefts view of mutual aid as being human nature comes from to this day highly influential scientific studies by Kropotkin amoung other things a respected scientist.
the rights view comes from economists running thought experiments. It's like being a modern scientist and trying to explain to an ancient greek that you need to test your hypothesis
"Aha but you see, if we assume everyone is a perfectly rational and 100% self interested..."