We constantly breed different desires, whatever they are. Our development depends on the level of these desires. In the beginning our desires are on the lowest level, the so-called animal desires. Later these are followed by desires for wealth, honor, social position and so on. On a higher level are the desires for knowledge, music, art, culture, etc. Finally, we find the more elevated desire for spirituality. Such desires gradually appear in the souls after many incarnations in this world or, as we say, with the development of generations. First the souls living exclusively in their animal nature life were incarnated in our world. Then, next generations of souls experienced the desire for money, honor and power. Finally, these gave way to the desire for sciences and for something higher that the sciences cannot provide.