“Biological sex isn’t important in daily life – most of us don’t even know what chromosomes we have.”
This objection, like many others transgender activists rely on, is superficially true – most of us haven’t had our chromosomes directly identified with a karyotype. But just because we don’t have a direct experience of our chromosomes themselves doesn’t mean biological sex is some great mystery! The vast majority of human beings – easily over 99.9% – can correct ascertain what chromosomes they do have by observing the unambiguous primary and secondary sex characteristics that result from those chromosomes. And these resulting characteristics are absolutely important in daily life; sex is one of the first things human beings recognize in others, and our ability to correctly determine sex from even the most subtle biological differences is quite impressive.
In this sense, our sex is a bit like our skin color. Do most people take the time to have their melanin levels scientifically measured? No. Does that mean our skin color is irrelevant, or that we can never truly know what it is? Of course not! Sex is the same way – while its biological basis might not be immediately obvious, its physical manifestation is extremely clear. Pretending that sex is irrelevant or inconsequential purely because we can’t examine our own chromosomes at will is just bizarre.
It’s also worth noting that transgender activists themselves acknowledge the social importance of biological sex whenever they complain about transphobia; after all, if biological sex was truly unimportant (or impossible to determine), male people would be able to identify as women and vice versa with no serious problems. The fact that trans-identified males are consistently treated as men and trans-identified females are consistently treated as women – despite their personal identification or the way they present themselves – demonstrates by itself that sex is both immediately obvious and socially relevant in the vast majority of cases.