Here, Clifford Geertz's recent work is instructive. He assumes that bees are genetically programmed to make honey and birds are genetically programmed to make nests, but humans are genetically programmed only to acquire language and culture. In this view, we are not fully human at birth. We haven't got all the stuff we need to cope in the world, to be social, to be moral, to be thinking, to be creative. The crux of Geertz's argument is that human nature is realized only in culture.
Human nature is the capacity to become Javanese, for example.
The virtue of Geertz's position is its lack of parochialism. Relativism in this sense argues for engagement, for dialogue between cultures. It's a deeper form of knowing that entails some recognition that I am one among others. I'm not the center of the universe. The effort in relativism is to determine what that other person is actually thinking.