Why has the human brain evolved to understand and do math. I see no evolutionary benefit of walking/tree climbing apes being able to do math ? Yet we are quite good at it. Why do we need things like numbers to hunt prey ? Biologically, it doesn't make sense ( to me at least )

Why has the human brain evolved to understand and do math. I see no evolutionary benefit of walking/tree climbing apes being able to do math ? Yet we are quite good at it. Why do we need things like numbers to hunt prey ? Biologically, it doesn't make sense ( to me at least )

 

Geometry of a sharp rock or arrowhead might be useful for hunting prey. Being able to make a 1:1 correlation between sharp rocks and members of the hunting party, or number of items you've gathered to bring back and the number of people you need to feed. Counting the number of opponents comes in handy for deciding whether to fight or run away.

What about more complex stuff ? I've heard that some other primates can somewhat imagine numbers, but do we use stuff like algebra, calculus, etc. Is it just some evolutionary byproduct of other adaptations ?

That traits that allow us to do mathematics is most likely just a by product of other adaptations that were selected for. An example of such an adaptation would be our linguistic ability allowed us to have recursive types of statements, it could have followed that understanding universal applicability of mathematical functions followed from similar mental abilities. This is a supremely oversimplified example, but hopefully it helps.