Intentionality and desire are different things and of the two it is desire that is prior - you can get to intentionality from desire, but not the other way around. There is no evolutionary creation of desire although desire is shaped by evolution which means that its forms are mediated by that which is subject to evolution. Desire is the great gift, the very spark of life. As a purely bodily phenomenon desire has no access to the being of its objects, it is lured and triggered by signs. There is a certain beetle that prefers to mate with old beer bottles. Only mind links desire to being, but the two are not in harmony.