In contrast to dualism, where opposites are complementary and equal. In a binary worldview, opposites are complementary and unequal.
In the Ancient Near East
"Among the Nilo-Saharan rulers (Kushites and Egyptians), the king was associated with the sun, and appeared with dark skin from sun exposure. It was believed that the sun bestowed strength and supernatural powers. His queen, on the other hand, appeared in public with a covering of white powder. She symbolized the lesser light, the moon. There was an understanding that the moon influenced the female reproductive cycle." Source
In the Old Testament
Has to do with the order of creation, the binary points toward its opposite. The prohibition of onanism: the seed that should fall on the ground is the seed of plants, the seed of man should fall in the womb. Likewise the prohibition of mixing fibers points to the order of creation. And the prohibition against boiling a kid in its mother's milk (mixing death and life).