The lesson of the long history of sexual specification is that life is not best served by reduction to a single strategy or morphology. What then is the ideal number of strategies or morphologies for a species? At the individual and embodied level the answer is: as many as there are individuals. Each one provides an element in an avenue to success, each is a contributing morpheme (to borrow a term from linguistics). But at the level of biological organization and morphological strategies of which individuals are only particular examples, the answer is: two. A strategy and its opposite, or mate. The positive and negative ions of an elemental structure.
These two will by necessity be in tention with one another. Their function is to pull the body of mass in opposite directions. But they will also contain fundamental attraction to one another. As between ions, each seeks their mate and compliment to achieve a balanced physical equation.
The important difference between this equation and a world involving only neutrons is that you achieve balance through the combination of complimentary charged particles, not through having only uncharged neutrons. The structure of life is ionic balance, not neutrality. It is an equation, not an integer. It is electricity, exchange, tension, not equivalence.
Of course, in order for the equation to balance, both ions must be of equal value. You cannot have an effective exchange, even in a complex interaction, if the value of one side of the equation doesn’t contribute or the other side doesn’t receive it. Relationships are much more volatile and unstable in some ways than inert particles. But they are also more powerful and tenacious, when their bonds are properly formed and maintained.
Making Nobody Happy 