Was there always just males and females


let me start with the caveats - I was on my 3rd beer, I was chopping onions in the kitchen and Discovery was on in the living room.

I think I heard them say that in the beginning, there were more genders than male, female and hermaphrodite…

something about evolution having selected the most successful sexes i.e. males and females and of course hermaphrodites. is this true, or was it just an onion fumes and beer induced hallucination?

  • a concerned hermaphrodite

Fossil records from the Castro district in San Francisco dating back to the Pre-Cambrian Era indicate at least 17 different sexes. Today the region is still home to at least 11, as the idea of reproducing with a different sex than their own has yet to be discovered.

Welcome to the boards, heynow; what a damn fine question!

I read a lot of SF and I have often wondered if the whole male/female thing might turn out to be only one way (out of many possibilities) to butter the cat; can we imagine any systems where more than two parents would be required?

Has sexual reproduction evolved more than once on Earth? (like the eye or legs or flight) - is sexual reproduction in plants and animals the result of descent from a common ancestor?

SWAG: Mangetout, sexual reproduction exists at the bacterial level with various genetic transfer methods. So I wouldn’t be surprised if all sexual beings evolved from a small set of sexual bacteria way back in history.

I’ve also heard of molds with more than two sexes, but I’m too lazy to Google it (even if I could come up with semi-intelligent search terms :)).

In his book The Player of Games, Iain M. Banks describes a fictional society with three sexes… males, with a penis; females, with a uterus (but no ovaries); and an apex gender, with genitalia described as something like “a vagina turned inside out,” and this gender had the ovaries. The way reproduction worked was that a male copulated with an apex, resulting in a fertilized embryo, and then the apex implanted the embryo into the female.

It was also interesting to note that this fictional society had the apexes as the dominant gender…

but er… why are we wandering into sci-fi? if evolution refined and redefined so many species, then why not genders?

even today aren’t there fish or sea-somethings that change their sex in between. then there is some sea worm which is female and has males inside her stomach (or whatever passes for a uterus) busy inseminating eggs…

then there are hermaphrodites that make perfect clones of themselves

i think its just presumptious to think that evolution didn’t play a role in determining gender also

what say?

I read a short story once in which an alien race had four genders. Three were “males” and looked pretty much alike. They were called (I think… it’s been a while) preparators, ovulators and impregnators. The preparator has sex with the female and his bodily fluids stimulate her body to be able to accept an egg. The ovulator then places an egg inside her and the impregnator impregnates said egg. The female carries the child to term and gives birth to it, but it has no genetic material from her, only from the three males. Not sure how the preparator’s genetic material got involved, though.

Wish I could remember the name of the story or the author’s name.

god that sounds so terminally convoluted… why wld you want to remember the name??

Well, it was a good story. Good doesn’t necessarily equal plausible, though.

The Puppeteers in Larry Niven’s Known Space series have three sexes; two types of male and a female, but it later transpires that the females are actually a different species altogether and that the pregnancy is an entirely parasitic one.

I suppose the key element of the two-parent model is that DNA splits into two strands, so each parent contributes half; is a coding macromolecule possible that would split into three parts?

who says pregnancy is anything less than parasitic in real life??? just cos the host survives…

Well hermaphrodite is actually both genders, isn’t it, ie male and female? Because flowers and stuff have sexual reproduction hence the huge disappointment in Biology class on discovering what “Sexual Reproduction” would cover… we had to wait another few months for Human Reproduction.

The other “gender” would be that producing asexually, or parthenogenically.

As I understand it, what defines male/female is sperm/egg. So seahorses that get pregnant are male, because they provide sperm. So for there to be another gender, there would have to be a three-way baby making scenario, where there was, eg:

(1) sperm
(2) egg
(3) trigger(?) regulator(?)

And (3) would be your third gender. I am not sure though if Nature has ever found it necessary to have more than two genders for successful reproduction. It would be fascinating to know if there was, though. Perhaps a scenario where the egg had 50% of chromosomes, the sperm had 25% of chromosomes, and the marm (I made this up) provided another 25%. Beings carrying marms would be known as amales, perhaps. I have no clue how the three of them would do the dirty, though.

no, actually what i think i heard was that there were like more than 10 sexes and this is where the beer zoned in and i kinda lost the thread of the show… either

  • sexes could mate with more than one sex i.e. there is no single ‘opposite’ sex


  • male could mate with female and Sex X and Sex Y and Sex Z… the ones best at fertilising and fulfilling the er… basic objective of reproduction were the male and female which cld only create other males and females and hence survival of the fittest

I suppose another possibility would be to have intermediate forms (like ferns and mosses, oh and in a way, those nasty things on the Alien Movies), but allow/require each of these intermediate forms to reproduce too.

Am I the only one who remembers “Alien Nation”?
George, the cop, his wife Susan, and Albert, the one who helped them conseave.
I remember things like that, but not my spelling leasons.

heynow - what I don’t quite get from that description, is that surely what defines gender/sex, as in “different” or “opposite” gender - is something that can be mated with. So what makes Sex X, Y and Z different from (mateable) females? Vaginas but no eggs? Ergo - are they in fact sterile females?

The main function of most life forms on this earth seems to be to survive, spread, reproduce, so I can’t get how there could be extra “genders” around that couldn’t reproduce, unless they were sterile or abnormally deformed versions of the male/female genders. Unless they were some sort of auxiliary gender, like the external stomachs of that jellyfish that are actually separate from it(??)

It seems to me that a minimum of two types of gametes are needed for sexual reproduction to perform the stirring up of genes. Possibly one could get by with a single gamete type, but still have two fuse together to make up a fertilised cell. Having more than two gametes involved is a very much-increased complexity for little extra benefit.

I can see that one might have auxiliary genders that are infertile – in the same way as worker ants and bees – but I guess that these options are really genderless.

Then there is polymorphism. This certain exists in the natural world with creatures of the same species have two or more significantly different body structures and or behaviours. There is often a significant difference in body size. I think that cannibalistic tadpoles are one example. The polymorphs reproduce in the normal way and produce offspring of both types.

Would it be possible to have a system of polymorphism where there are two males (A and B) and two females (A and B) where :

male A+ female A -> male A
male A+ female B -> female A
male B+ female A -> male B
male B+ female B -> female B

Here each of four sexes all need each other to produce both male and female of the same type.

Agreed, but I wonder how much of that is predisposed by the precise chemistries that life on Earth chose to use; if the coding macromolecules were vastly different in structure and/or behaviour (assuming, of course, that this is even a possibility), then it might have ended up being simpler to have three genders or more.

It’s also important to consider that evolution doesn’t always result in the adaptation that is the best that is logically possible from a design view, to a large extent it has to work with what already exists, so the final solution is often not an elegant or minimalist one, just one that works OK.

On strictly biological grounds it seems implausible. Why have sex at all when the best way of reproducing your genes is asexual cloning? The most convincing currect theory is that sex, which involves giving your descendants only half your genes, is successful only because it speeds up evolution. So to have a third sex would involve diluting your own genes even more, while probably not significantly speeding up evolution. Not to mention all the practical problems.

All these postulated “facilitator” genders are implausible, because they get no benefit from their role in reproduction. The genders that produce the gametes are the ones that actually reproduce, the others are essentially sterile. The only way they could evolve is through some sort of eusociality, like with sterile worker ants and bees. You could consider the sterile female workers a third gender, since they are genetically distinct from the fertile females and fertile males. Workers are X0, females are XX, males are XY. Workers are produced when eggs germinate without fertilization, meaning that the workers are much more closely related to the queen than her sexually created daughters and sons. That means that it can make more sense for the workers to help the queen raise sons and daughters than it does for them to try to raise their own.

But keep in mind that the distinct division between genders that we see in mammals isn’t neccesarily the most common way to do things. Many, if not most, animals are capable of producing both eggs and sperm. Some produce eggs at one point in their life cycle, and sperm at another. But what is the difference between sperm and eggs? The main difference is that sperm are motile, and eggs aren’t. There are some species that are isogamous, meaning that they only produce one kind of gamete, a large motile one. But this is somewhat inefficient, since it is essentially creating motile eggs. Probably the first sexual animals were isogamous, but quickly evolved two gamete forms.

But why require two gametes to fuse to form a new organism? Why not three, or four, or five? Well, the real question is why you would require two, instead of one. Many organisms get by just fine without sexual reproduction. And it is something of a mystery why an organism would go to all the trouble of sex to produce an organism that is only half related to them, instead of 100%. The most common explanation is that sexual reproduction speeds up evolution and produces more variation. But there is a price, you children are only half yours. Sexual reproduction is worthwhile, but not overwhelmingly so. Requiring a third gamete is riskier and more complicated, and your children are only 1/3 yours. It seems that once you’ve got the simplest version of sexuality you’ve done enough to get all the variation you’ll ever need and more. Increasing that is only going to cause problems, and won’t solve anything that having two forms of gametes already solves.