“Evolutionary psychology is about adaptation to one’s environment. Where cultures differ environments differ...”
This doesn’t sound like evolutionary psychology to me. It sounds like just regular old psychology.
Your point re: noise in EP experiments is well taken. But if EP can’t be tested by experiment, what use is it?
The human brain is a product of evolution. But as Tim Tyler and Aaron pointed out, any particular human brain is also the product of a developmental process that happens in a memetic environment. Given the brain’s plasticity, I’m leery of claims that concepts like “fairness” are evolved—especially when that concept varies widely among cultures and individuals.