Male and Female
Humans are mammals and, like all mammals, propagate the species through a process known as sexual reproduction. Each human is of one of two sexes, male or female, and the sex of any given human is readily and unambiguously identifiable at birth based on obvious anatomical distinctions.
[I’ll say this once and then not mention it again: this is a discussion of normal humans. Just as one can say that humans are born with two arms and two legs, one can say that humans are born as one or the other of two sexes. A small number of humans are born without the normal number of arms or legs, and a small number are anatomically ambiguous as regards sex. But normal humans, and that’s the vast majority of humans, are as described.]
There are distinctive physiological characteristics associated with male and female humans. Males tend to be larger and stronger than females; only females can give birth to offspring; males tend to be more aggressive than females. These are traits that humans have in common with many other mammals, and derive from biology, from the effects of various hormones on the male and female bodies during development.
Males and females play distinctly different roles in reproduction. In particular, the physiological investments made by males and females is quite different: for males, reproduction has essentially no cost associated with it; for females, reproduction is costly both in terms of time and physical investment. It follows that the mating strategies of males and females will likely differ: because reproduction for them is inexpensive, males will seek to reproduce as often as practical and with a wide variety of females; females, for whom reproduction is costly, will of necessity reproduce less frequently, and will tend to be more selective in their choice of mates. This will inevitably lead to different and characteristic behavioral patterns for the sexes.
Beyond those characteristics attributable to physiology and evolutionary pressure, there are additional sexual traits that may be essentially random, not readily explained by biology. These so-called cultural distinctions may, unlike differences rooted in biology, vary from culture to culture and change over time.
There is a constellation of traits which we associate with sex. Those which we associate primarily with males are referred to as masculine traits; those associated primarily with females are referred to as feminine traits. While the sex of any given person is either male or female, the degree to which the person exhibits qualities considered masculine or feminine may vary quite a lot.
A male who exhibits qualities normally associated with femininity is still a male: no matter how feminine he may seem, he does not ovulate, and he can not give birth. Similarly, a female, no matter how masculine, remains a female: she does not produce sperm and can not fertilize an egg.
Gender Diversity and Trans Movements
Gender diversity is the idea that there are more than two sexual states for humans. Gender diversity attempts to assert a quasi-sexual dimension, “gender,” independent of, and not constrained by, biological reality. Humans are male or female, distinctions rooted in biology: other so-called genders are expressions of whim, fantasy, confusion, or sincere but mistaken belief in non-existent human variety.
The trans movement asserts that humans can change their sex, either through pure volition (whim), or as a result of drugs and surgery. In fact, people can alter, to some extent, the degree to which they express typical masculine and feminine traits, but they can not change their sex: males remain males; females remain females.
Identity Versus Quality
Both the gender diversity movement and the trans movement are sexual identity movements. That is, both are founded on the assertion that one can claim a sexual identity, and that making the claim is itself sufficient to assume the identity — and, importantly, that no challenge to the legitimacy of the claim is possible. In that sense, such claims are metaphysical, untestable, divorced from biological reality, divorced from qualities of masculinity and femininity.
It is important for these movements that they make claims of identity, and not of qualities. Claims of masculine and feminine qualities can be evaluated objectively. Claims of identity are essentially legal or political claims which, if left unchallenged, grant individuals status which their inherent qualities might preclude.
To pick a topical example: a man who declares himself to be a woman, and who is then given the same status as a woman and so allowed to compete against women in athletic events, will have an enormous advantage, because he possesses essential masculine qualities of bone size and density, connective tissue, muscular development, etc.
False claims of sexual identity — men claiming to be women, women claiming to be men, anyone claiming to be neither man nor woman — should be rejected. If we wish to accommodate claims of special status based on measurable physical traits, on objective qualities of masculinity and femininity, that is a different issue. But false claims of sexual identity are a way of assuming a status predicated on sexual qualities while precluding any evaluation of those qualities. This will inevitably lead to problems, including the kind of athletic cheating currently in the news, and to needless confusion and ambiguity.