6 sexes?
June 28, 2006 9:30 AM   Subscribe

How many sexes are there?

I came across mention of a theory a few years ago that argues that our theory of intersex are woefully inadequate to the evidence. This scientist argued that medical researchers have identified six different sexual variances, presumably including intersex and hypersex individuals. I'm trying to track down information about this theory of sex, and coming up empty-handed. Does anyone know more about it? Specifically, I'm interested in the sexual categories and their causes: chromosonal deformities, in utero hormonal imbalances, etc.
posted by anotherpanacea to Science & Nature (17 answers total) 7 users marked this as a favorite

Best answer: The Intersex Society of North America might be a good place to start.
posted by ThePinkSuperhero at 9:35 AM on June 28, 2006 [1 favorite]

Best answer: I've heard mention of five sexes, and googling reveals "The Five Sexes: While Male and Female Are Not Enough"

She doesn't seem to mention chromosome specifics there, but AFAIK there's XX, XY, XO, XXX, and XXY.
posted by needs more cowbell at 9:39 AM on June 28, 2006

*why, not while.
posted by needs more cowbell at 9:40 AM on June 28, 2006

I think the definition of what a sex is needs to be answered first. If the definition is what it takes to reproduce a species, there are only two. If the definition is related to the different characteristics which are expressed by sex-linked genes and sexual behavior, there may very well be more.
posted by Ironmouth at 9:42 AM on June 28, 2006

If one were to decide based on karyotype rather than on which organisms produce the larger gamete, then we would have to conclude that women (with two of the same type of sex chromosome) are the same sex as roosters (who also have two of the same type of sex chromosome, whereas female chickens have two different types of sex chromosome).
posted by grouse at 9:47 AM on June 28, 2006 [1 favorite]

(I should add that there are other things besides sex chromosomes that can contribute: one interesting thing is Androgen Insensitivity Syndrome, wherein a person has XY chromosomes but may appear entirely female, or even hyperfeminine.)
posted by needs more cowbell at 9:47 AM on June 28, 2006

Response by poster: From the Intersex Society link: "How Sexually Dimorphic are we?":

XXY, XO, XYY, XXYY, XX males, 47,XXX females. Plus plain old XX and XY. That's 8! Oh, well. This doesn't include things like Androgen insensitivity or other developmental issues. Thanks all!

I'd still love to hear if anyone knows the 6 sex theorist, but obviously that's a gross simplification.
posted by anotherpanacea at 9:52 AM on June 28, 2006

I agree that specification what you mean by "sex" is.
For example, someone can be born XY (male) and yet their phenotype can be a female (should be XX- aka androgen insensitivity). Or the other way around- born XX and develop as a male (lack of estrogen production causing an excess of androgen.
You can define it by reproductive possibility, phenotype, genotype, combinations thereof, sexual organs (typically, ovaries = female and testes = male...yet, once again, not always that cut & dry...can have (usually rudimentary) ovaries and be XY genotype yet look like a female OR male and...ok, I'm not really sure about that, but the sexual organs could still be a factor in your definition of "sex." It is these organs which contribute greatly to one's phenotype with the X & Y chromosomes causing development or lack thereof- testes with development causing repression of ovarian production due to genetic repressors they send out. Based off an old experiment where some scientist removed sexual organs from an animal to test the "default" pathways of mammals).
posted by jmd82 at 10:29 AM on June 28, 2006

jmd82, aren't XX people that develop as male usually the result of a translocated SRY gene (translocated to an X chromosome)? It sounds odd that low estrogen production would lead to someone developing near-completely male.
posted by needs more cowbell at 10:41 AM on June 28, 2006

There's 3. Sex is a reproductive variable, either you impregnate, get impregnated, or do it to yourself. End of story.
posted by ewkpates at 11:20 AM on June 28, 2006

ewkpates: You forgot "can't impregnate nor get impregnated." By your criteria, there are four.
posted by Mozai at 12:23 PM on June 28, 2006

I think ewkpates is on the right track here...by "sexes", is the OP meaning actual genetic genders or enacted seualities?
posted by Thorzdad at 2:29 PM on June 28, 2006

Best answer: jmd82, aren't XX people that develop as male usually the result of a translocated SRY gene (translocated to an X chromosome)? It sounds odd that low estrogen production would lead to someone developing near-completely male.

Both can happen, depends on what's going on in the person. The SRY translocation/mutation is probably more straight forward, but an hormone inbalance can lead to phenotypically male (possibly due to estrogen insensiticity rather than androgen oversensitivity?). The idea of the female 'default' pathway is being overturned as it is realised there are specific switches needed to push female development.

I assume the question is focussing on human sex, as anything wider becomes too complicated. In which case it can be almost infinite. Take into account the difference between sex determination (are you genetically male or female or ...) and sex development (what phenotype do you end up with?), either of which can be messed up in many ways. Sure, the majoority of people fall into the two 'normal' sexes, male and female, and everything else can probably be considered a spectrum between them. But there's definitely more than six set types.

Some examples. You can be genetically XY and phenotypically XX to the point you can reproduce as a female. You can have more or less than two sex chromosomes (XXY, XO, etc). You can be male on one side and female on the other (classic hermaphroditism). You can even be born one gender and develop into another. Basically, think of a scenario, there will be cases out there.

This doesn't even begin to touch on gender (what you identify as) or sexuality (who you want to shag). Those are additional factors that add even more layers of complexity. The more I study biology the more I discover that what is possible or even normal is far greater than would be expected.

I took a postgrad class in this last year. I don't really have layperson references (although Dr Tatiana's Sex Advice to All Creation is very good), but I do have all kinds of scientific journal articles sitting around if anyone wants copies.
posted by shelleycat at 3:17 PM on June 28, 2006

A link from the intersex page posted up there goes to this page about fetal development from the sick kids hospital in Canada. It's very good, easy to understand, pretty much scientifically correct, and gives insight into why sex is all so messy.

Basically, the fetus starts out as bipotential, ie has no sex but has the potential to become either sex. Genes turn on at a specific stage of development that cause the gonads to develop into testis or ovaries. This is sex determination. That gonad then produces formones that drive further development of the fetus to beome the set gender. This is sex development. So problems with the genetic switch can lead to the wrong hormones being made (or no hormones) and problems with hormone balance or hormone action in the body can lead to the wrong phenotype being developed. These are all complicated, highly regulated cascades, ie lots of genes and hormones and proteins etc involved, so there are lots of places things can get messed up and lots of things working to stop it getting messed up.

The primordial germ cells, cells that become either eggs or sperm, are also bipotential. They migrate to the gonads where the hormones make them form the appropriate gamete (egg or sperm). This is why a genetically male, phenotypically female person can end up with eggs (the female hormones are what drive the choice), and become a mother. This is rare though because everything esle has to develop properly too. It's more likely that problems with the pgcs will lead to infertility.
posted by shelleycat at 3:36 PM on June 28, 2006

shellycat's link is great.
posted by tula at 12:04 AM on June 29, 2006

seconding shellycat's link. awesome.
posted by anonymoose at 3:12 AM on June 29, 2006

Response by poster: Thanks everyone. For the record, I'm 1) concerned with humans, and 2) interested in the various categorical strategies people use to define sex, not gender or sexuality. So: functional, anatomical, genetic, etc. That's why the notion of "6" specifically is troubling me: I can't figure out what they would be. Five I get: m/f/inter/hypermale/hyperfemale. Eight, as I pointed out in my last comment, makes sense from the chromosonal perspective, and the fifteen-plus you see by charting the various developmental tracks also makes sense to me. But six? I'm guessing that's starting with five, so it's basically anatomical/hormonal. But where'd the sixth one come from? Some sort of neuter/asex?

Anyway, thanks again for all the answers. PS- I love Tatiana!
posted by anotherpanacea at 9:46 AM on June 29, 2006

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