It doesn't defy anything. And evolution doesn't define everything. There are a wide range of cultural values that are possible given our evolutionary heritage. We evolved only the capacity to have a culture, and that could be almost anything. We can override our "programming" because we are intelligent enough to do so. For instance, suicide would seem to be a trait that evolution would discourage, but in some cultures like the Samurai of Japan, suicide in some contexts was considered a virtue.