Question about evolution...(maybe mature audience, I don't know)

If there was no almighty God, and the universe was created by star dust and atoms blowing up; then can someone explain this one thing to me: Sex. Why does it exist? Why are there only two genders?

Since there is sex, there must have been a reason for it. Right? And isn't that reason was to populate the earth?

My reading eyes might not be in today, but what was the question in your post? You pretty much answered it yourself in that it is to populate the earth.


There are two genders simply because God or Evolution, or any other higher being/explanation just made it that way. Asking why there are two genders is like asking what the meaning of life is. Nobody really has an answer.

Oh, and correct me if I'm wrong, but there is one fish with three genders. I think it's Male Female and Super-Male or something along those lines. Don't quote me on it.

Originally Posted by BB_11

My reading eyes might not be in today, but what was the question in your post? You pretty much answered it yourself in that it is to populate the earth.


There are two genders simply because God or Evolution, or any other higher being/explanation just made it that way. Asking why there are two genders is like asking what the meaning of life is. Nobody really has an answer.

True, I did answer my question(s), but then I would like someone to explain it then. I don't think evolution could make there two genders because it was all star dust and things in my closet.

As you requested, I won't quote you on the fish thing.

Originally Posted by Naruto Uzumaki

If there was no almighty God, and the universe was created by star dust and atoms blowing up; then can someone explain this one thing to me: Sex. Why does it exist? Why are there only two genders?

Since there is sex, there must have been a reason for it. Right? And isn't that reason was to populate the earth?

Sex is very beneficial to organisms. To be brief, it eliminates detrimental mutations much more quickly than asexual reproduction, and increases genetic variety.

Sexual reproduction consists of the DNA of two organisms being mixed and matched, and a new organism resulting with this entirely new genetic structure. In a population that reproduces asexually, a bad mutation will cut off an entire line of descent. Sexual reproduction gives organisms a way around this - Some of the offpsring may have a mutation, but others won't, and this will ensure genetic continuity.

Why only two sexes? Well, 3 sexes would be beneficial in terms of variation, but this is outweighed by the sheer difficulty in getting 3 organisms to fit together to reproduce. Two sexes suffices.

Of course, even in humans, we have genetic disorders that I guess could count as other genders (although most are infertile anyway). People can be born with XXY or XXX chromosomes. XXY (Klinefelter's syndrome) results in a man with breasts and a lot of female features - basically half man, half woman. XXX causes too much estrogen, and although I've never read about the specifics, I think most cases are infertile.

In terms of the origins of sexual reproduction, many simpler forms of life use both sexual and asexual reproduction, and some are hermaphroditic. I guess these can give you an idea of the transition towards sexual reproduction. If you want it explained more clearly though, I'd be happy to.

Originally Posted by Mad Hatter

Why only two sexes? Well, 3 sexes would be beneficial in terms of variation, but this is outweighed by the sheer difficulty in getting 3 organisms to fit together to reproduce. Two sexes suffices.

AHHH!! Three-some! Sorry immature moment. But seriously 3 sexs would be quite confusing and how would anyone know which sex to mate with?? If there was going to be more than 2 sexes there would have to be 4 or some other even number or 1 sex would die out. Unless one of the sexes could mate with BOTH the other 2. The whole question is quite confusing. It's like your asking why are we here?? Which nobody knows..

Knowing something and believing something are two different things. Though a belief is true to the beholder. Have fun with your meaning of life. You'd make a fortune if you told theologians and scientists!

I think House MD can answer this question substantially.

"Sex COULD kill you. Do you know what the human body goes through when you have sex? Pupils dilate, arteries constrict, core temperature rises, heart races, blood pressure skyrockets, respiration becomes rapid and shallow, the brain fires bursts of electrical impulses from nowhere to nowhere, and secretions spit out of every gland, and the muscles tense and spasm like you're lifting three times your body weight. It's violent. It's ugly. And it's messy. And if God hadn't made it UNBELIEVABLY fun, the human race would have died out eons ago." - Dr. Cameron

Originally Posted by Mad Hatter

Why only two sexes? Well, 3 sexes would be beneficial in terms of variation, but this is outweighed by the sheer difficulty in getting 3 organisms to fit together to reproduce. Two sexes suffices.

To expand on that, there are other coupling patterns that prove equally unfeasible.

For example, if we had three species, of which any two of which could couple with each other for procreation, "survival of the fittest" would dictate that two would typically prefer each other over the third. Thus the third would effectively be "bred out" over time (e.g. intronically discarded).

Alternatively, if we have one alpha sex that could procreate with the two others, we either have a situation where the populations are equal, which would effectively cut procreation down to a fraction (for the alpha sex being commodity), or if the alpha sex is naturally born at a higher rate, we'd see it naturally opt for one of the other genders over the other: Again, survival of the fittest.

Even in the scenario of three sets of genes required for procreation, as described, we also have the side-effect of increasing the rate of genetic normalization within populations.

Of course, we may one day discover any one of the above three gender scenarios in nature, but the complexity described still explains why we have yet to.

If evolution were true, then I'd expect to see only one gender and not two. Wouldn't it be easier if you could just have your own child when you wanted and not have to rely on another person? That makes more sense, to me.

Originally Posted by D3PyroGS

If evolution were true, then I'd expect to see only one gender and not two. Wouldn't it be easier if you could just have your own child when you wanted and not have to rely on another person? That makes more sense, to me.

Natural selection works just as much on populations as it does on the individual. Since sexual reproduction is very beneficial to the population, populations with sexes are more likely to survive than those without them.

Of course, there are some populations that have stopped sexual reproduction. A type of lizard (I can't remember the name off the top of my head) reproduces with unfertilized eggs. There are no males, but the females still mount each other in a mating ritual. I guess this is a situation in which the natural selection on the individual is stronger than that of the population.

Originally Posted by Mad Hatter

Natural selection works just as much on populations as it does on the individual. Since sexual reproduction is very beneficial to the population, populations with sexes are more likely to survive than those without them.

Not only that, but since a primary function of sexual reproduction is to unite and mix divergent branches of a species, two sexes makes much more sense than three or more. With two, if two slightly genetically deviant members of a species meet by chance, they can mate and possibly produce offspring with the positive characteristics of both. Three sexes would require three animals coincidentally meeting at the same time - not nearly as likely.

Since sexual reproduction is very beneficial to the population, populations with sexes are more likely to survive than those without them.

But I mean a race with one sex that can reproduce at will. It would make much more sense, evolutionary-wise.

Originally Posted by D3PyroGS

But I mean a race with one sex that can reproduce at will. It would make much more sense, evolutionary-wise.

Elaboration as to why would help.

Many species produce asexually. Many others are dimorphic. In both cases sexuality is suited to the nature and role of the species being considered. Consider why it may be beneficial to have one gender that can bear children, and one that can't. From that, how might it be advantageous for one gender to be colored according to their environment, and the other stand out in stark contrast? One made to look small and non-threatening versus large and dangerous?

Or, if it helps to look at things the other way around, what might happen to a species where every member can become pregnant?

"Sex COULD kill you. Do you know what the human body goes through when you have sex? Pupils dilate, arteries constrict, core temperature rises, heart races, blood pressure skyrockets, respiration becomes rapid and shallow, the brain fires bursts of electrical impulses from nowhere to nowhere, and secretions spit out of every gland, and the muscles tense and spasm like you're lifting three times your body weight. It's violent. It's ugly. And it's messy. And if God hadn't made it UNBELIEVABLY fun, the human race would have died out eons ago." - Dr. Cameron

You all do realise that this quote made this topic basicly done, don't you?


Well frogs are doing quite ok I think and they can change gender according to what is necesarry to reproduce.

But I think that the reason only one member can become pregnant as pregnancy takes a lot of energy and the need for food doubles. So from a survival point of view it would be reasonable to think that one member becomes pregnant while the other member takes care of the pregnant member. If both members would be pregnant than survival chances would slim as both members needed a substantial amount of extra food which may not be available.

"Sex COULD kill you. Do you know what the human body goes through when you have sex? Pupils dilate, arteries constrict, core temperature rises, heart races, blood pressure skyrockets, respiration becomes rapid and shallow, the brain fires bursts of electrical impulses from nowhere to nowhere, and secretions spit out of every gland, and the muscles tense and spasm like you're lifting three times your body weight. It's violent. It's ugly. And it's messy. And if God hadn't made it UNBELIEVABLY fun, the human race would have died out eons ago." - Dr. Cameron

Ha. Half those things happen when you play an intense game of basketball or any intense sport.

Elaboration as to why would help.

Hmm. I simply meant that it would have been easier for Evolution (as a process - I certainly don't agree with it) to have made one gender and not two. It takes two to continue the race of X-animal, while it would make more sense, natural selection wise, for one animal to be able to reproduce at will. I hope I am being understandably clear.

Originally Posted by D3PyroGS

Hmm. I simply meant that it would have been easier for Evolution (as a process - I certainly don't agree with it) to have made one gender and not two. It takes two to continue the race of X-animal, while it would make more sense, natural selection wise, for one animal to be able to reproduce at will. I hope I am being understandably clear.

But two sexes allows for more changes, more changes increases the likelihood of a beneficial change, which leads to a species surviving longer. There are quite a few animals that do reproduce asexually, but they tend to have few predators or easy access to food, so they don't need to change.

Besides, having too many animals is bad for the ecosystem, it leads to a lack of food, and an increased spread of disease, which makes having two sexes to limit the number of population make even more sense.