My wife is fond of telling me that we all start out female, and that men (XY) are essentially abnormal women (XX). Much as I hate to admit it, she's basically right, as I suppose my nipples were telling me all along. The sexual organs of all mammals start off on similar lines, so embryonic males and females look the same -- they are "sexually indifferent" to use the formal term. For instance, our external genitalia derive from the same precursor: The nub ("genital tubercle") that will become either a penis or a clitoris is androgynous in the early embryo. Similarly, the scrotum is basically the labia majora with longer, folded and fused lips (which explains the odd "weld" along the centerline of a man's scrotum).
In humans, the precursor sex organs, or gonads, start to differentiate into either ovaries or testes at about the eighth week after conception, which is when the "normal-abnormal" split happens. Male testes secrete androgens such as testosterone; add androgens and you get guys. Females develop in the absence of androgens, so in nature, women are the default.
That's unlike in the English language, which takes the opposite tack. Linguists use the term marked to distinguish between a root, or dominant term (happy) and a secondary, derivative term (unhappy). In this case, "unhappy" is marked. Where gender is concerned, the default is for "man" words to be unmarked and "woman" words to be marked, or derivative. Take the two words I just used: "man" is the norm while "woman" is marked (Old English wif + mann). (It would be tempting, but wrong, to make the same case for male/female. They're not related etymologically.)
So we have, for instance: host/hostess; waiter/waitress; heir/heiress; god/goddess; count/countess; actor/actress. (Oscar nominee Alfre Woodard says she calls herself an actor because "actresses worry about eyelashes and cellulite, and women who are actors worry about the characters we are playing.") I'm hard-put to find a counter-example: stripper/male stripper?
Going beyond language, my wife, Louisa Rogers, may be said to have "kept her own name," but I don't recall anyone commenting that I kept my own name when we got married. And when I was young, before the liberating introduction of "Ms.," women were marked by their marital status: Miss and Mrs. And on and on. But while our culture has made men the unmarked gender, nature knows best. Biologically, women are the norm.
Barry Evans (email@example.com) spent much of his youth worrying about his weld.