[fabian2k]

Scientists tend to understand that part, that's more of a political/cultural thing (I'm ignoring the language part here entirely about which terms to use for which concepts here).

There's the X and Y chromosomes, those produce a binary result (unless you have a genetic anomaly). And after that comes the messy and fuzzy parts I mentioned, where those genes trigger changes in hormone levels and development. And those parts are analog, very complex and contain a lot of different parts. So the outcome is not binary anymore.

[altruios]

...well actually...

There are more combinations than merely having only X, or an XY combination. And there is more fuzziness even in the Y and X expression, as you said. It's fuzzy all the way down. The tale of Binary results has always been from compression of reality: Always has been.

[grey413]

As it happens, in humans there is a single gene on the Y chromosome, named SRY, that typically switches on male-linked traits.

But you're right, the full range of biological possibilities is very fuzzy . SRY itself a just a regulatory switch that other sex-linked traits are conditionally dependent on. If the switch gets broken, you develop as female. If genes that support the switch break, you might develop as female. If a sex-linked trait downstream from SRY mutates, then pretty much anything can happen. And other species do sex determination completely differently. Hell, a lot of bacterial sex basically involves throwing pseudo-viruses at each other.