The concept of “biological sex” is bullshit. When talking about trans people and the sex they were assigned at birth, the terms “biologically female” and “biologically male” are often thrown around without any critical interrogation into their meaning. They’re a fallback for a lot of people who are aware that saying “born female/male” is reductionist, but who haven’t yet done the work to find more accurate terminology. (The terminology I use and recommend is “assigned male/female at birth”). For a variety of reasons, “biological sex” is a faulty concept, rife with scientific inaccuracies, that subtly undermines and invalidates trans identity. Like a pointillist painting, the closer you examine the concept, the more you realize it’s just a cluster of meaningless points of observation, designed to trick you into seeing a complete picture that was never really there in the first place.