2 ms·
The tl;dr: The species has two chromosomes that act like sex chromosomes. That is to say, our Y chromosome never get's to mingle with other Y chromosomes, and
by swsieber 10y ago
The tl;dr:
The species has two chromosomes that act like sex chromosomes. That is to say, our Y chromosome never get's to mingle with other Y chromosomes, and so it accumulates mutations fairly quick, and thus a sex chromosome. In the bird species, there are 2 such chromosomes, and thus 4 unique states with regards to those unique chromosomes, as opposed to our 2 states.
They are defining sex not through sexual organs, but through the chromosomal state.
- astrodust 10y agoIt's a very interesting combination of factors here, and they're also making the observation that this could be how the original XX/XY split occurred. Sexual genetics are actually a lot more complicated than people think. There are YY "supermale" people, though it's more common in fish which gender-flip depending on population balance leading to XY males breeding with XY females. A YY male will always produce male children. There's also XXY, XXXY and so on which is where things get even more complicated.