It's SO much more complex than this biologically, BillyG. What about people, for example, who are born with indeterminate genitals, or genitals of both sexes? There's a whole range of possibilities that your formula doesn't account for.
“Everybody’s Inner Being is Pure Happiness”, MMY. This inner happiness is consciousness itself, being formless it takes on bodies of a Male or Female nature in alternating incarnations on Earth to learn the lessons of life. Being incarnated sometimes Male and sometimes Female gives the formless Soul the full opportunity to experience the full range of experiences of the heart (female) and mind (male). This brings in to question the ‘erroneous’ idea that one can be born “in the WRONG sex”. How can the soul, being sexless, be in the wrong sex? In addition, how can one really ‘change’ one’s sex? Surgically one can remove sexual organs and chemically/hormonally grow breasts, but how about the subtle nature of the physical body, yes, the etheric body? It is said in esoteric literature that the WHOLE man/woman is both negative or female AND positive or male! In a Man the outer physical body is positive or masculine and his subtle etheric body is negative or feminine/passive; conversely in the Female the outer physical body is negative/feminine and the inner subtle body is positive or masculine. Can science eradicate or alter ‘these’ characteristics of the soul? Until modern man can understand the inner nature of man and his subltle bodies he will be unable to understand the nature of the soul and the mistaken notion that the soul can be born ‘in the wrong sex’, IMHO.