Thank you for the clearification!
**I don’t know much about “humanism”**except from sources that are likely to be pretty biased.
As far as altruism from evolution, I think what makes sense is whatever behavior perpetuates and grows the species.
All of our ancestors had one thing in common: they lived long enough to reproduce. They had to work together as a team to some extent to overcome nature’s challenges and proliferate or by definition they don’t end up as out ancestors and the genes that drive that behavior are out.
Have you ever seen the movie, “The Gods Must be Crazy”? The first part is my favorite, where they show a village of “bushmen” who have a simple nomadic life, until a modern “miracle” drops into their midst – a coke bottle from a plane overhead. Then they become materialistic and selfish.