In nature the truth is expressed. In modern society we are surrounded by abstractions, concepts and doctrines which serve the human imperatives of economic, societal and power structures. Sex has as its function the perpetuation of life and in the case of humans this primary purpose is required to serve a species where the offspring require huge investment from the parents to bring them to a state where they can in turn breed. It is understandable that in modern society a trans sexual reaction is increasingly common as we have strayed so far from the natural world we came from. If you wish to explore these ideas further (and better expressed than I can) I would recommend reading the 'The Naked Ape'.