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Comment by appleflaxen | Hacker News Reader

Serious question; I hope it makes sense: What makes these "sexes" and not just "individuals"?

To elaborate a bit: when I read the description, it sounds like a person could make the same claim about humanity: "there are billions of sexes: John, Jane, Tim, Judy, Juan, Maria, etc etc"

How is this different? Or equivalently, what makes a "sex" a "sex" if it's just variability within the sex chromosome, but every individual is able to create progeny with 25% (?) of other individuals.

To me, that sounds like 4 sexes.

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A DNA sex is a set that can merge successfully with another set that produces an offspring. This is not always possible in all life because some sections of the DNA are incompatible when swapped.

Here is the sparrow with four sexes: https://www.nature.com/news/the-sparrow-with-four-sexes-1.21...

Conversely, what we think of sex (the genitalia and dimorphism identification) may not even be defined specifically by genes sets, but by epigenetic/environmental responses.

Even though alligators have DNA sets that are swapped, they are largely physically sexed by temperature: https://en.wikipedia.org/wiki/Temperature-dependent_sex_dete...

It even has an advantage, as females without mates can sometimes spontaneously reproduce and have offspring that are both male and female: https://en.wikipedia.org/wiki/Parthenogenesis_in_squamata

> what makes a "sex" a "sex" if it's just variability within the sex chromosome, but every individual is able to create progeny with 25% of other individuals?

I haven't read the article yet (looks like it's been DOSed by traffic from Hacker News?), but your criterion would be met in a population of 201 entities (numbered from 0 to 200) where each entity X can procreate with entities in the range [X-25 ... x+25] (mod 201, of course). That would arguably yield 201 distinct sexes, where each individual is sexually compatible with 25% of the population.

If a mapping between compatible sexes existed such as in your example, it would be more useful to think of sex as continuous spectrum rather than a discrete collection.

Perhaps. But only because the mapping I've defined has so much symmetry.

Instead of the range [X-25 ... X+25], assign to each sex a random one of the 200-choose-50 (4.6 * 10^47) possible groups of partners sexes with size 50.

It would be impossible to completely describe the set of sexual compatibilities without simply enumerating them, and therefore necessary to treat the sexes as a set of discrete entities.

That's why I wrote "such as in your example."

I think that if each individual was randomly compatible with some subset of the population, we don't have 200 sexes, we have one sex and a 25% fertility rate.

There are 20k different sorts of genitals. More seriously, it would be chromosomal differences I guess.

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