rounser said:
If hermaphrodites were as successful as males and females, they'd be everywhere, and females and males would be nowhere.
Well, first off, they are everywhere. Take a shovel, dig up some dirt. The earthworms worms you see are true hermaphrodites. Given that, in terms of biomass there are more hermaphrodites on land than there are vertebrates. So much for them not being successful.
The specialists always tend to win; that's the way evolution usually works...
Then why are there still so many earthworms?
Not true. If hermaphrodites could compete with males and females, the biological chemistry would find a way to do it over those hundreds of millions of years.
There's a common misconception - that if a solution is even throetically possible, evolution will find it. This is simply not true.
Evolution is not driven by a thoughtful mind - it does not say, "This would be advantageous, so I will do it". Evolution does no
seek advantage. Evolution must happen on a trait by chance, and that trait must be advantageous (or at least not harmful) at the time in order for it to come to be part of a species. A great many unlikely things have come up during the course of terrestrial evolution, but there's many things that also haven't come to pass. Evolution does not try every possible solution. It only tries the ones it happens to stumble across.
If being a hermaphrodite were better than being a male or female, I guarantee you that there would be almost no males or females in the human race...only about as many hermaphrodites as exist among humans now.
Perhaps you weren't reading fully - there are no true hermaphrodites among vertebrates now. Not because it's disadvantageous, but because it's not physically possible. The presence of active testes causes deformaties in ovaries, and vice versa. Getting to a state where that is not the case requires a fundamentla restructuring of how the testes and ovaries work. This is not exactly easy to do without killing the organism, or making it sterile.
The nature of sex is fundamental to our existence; it's the very beating heart of evolution. To pretend that it's a spandel (a left over trait, an accident with no purpose like having a chin is inevitable if you have a jaw) makes no sense.
Well, hermaphrodism does not at all change the nature of sex, in that it still allows for the remixing of genetic material.
Nobody said it had no purpose. I said that, now having it, it is nigh impossible to change. There are any number of things in the land-vertebrate body plan that are similar - bilateral symmetry, or having four limbs. We are stuck with the basic body plan of our ancestors because radical alterations are not easy to do, while subtle alterations are.
As you put it, the method of our reproduction is fundamental. Therefore, changing it is nigh impossible. Consider that the trait must result in a fertile cross-fertile with non-hermaphordites. The trait must be heritable - when it mates with normal members of the species, tyhe results must at least carry the potential to produce later hermaphrodites. It must also be able to mate with normal members of it's species - for example, a critter who had the full set of male and female parts would also emit both male and female pheromones, which might well exclude it from mating. For humanoids - how likely are you to make with another human who has both sets of genitalia?
Something so core to how our species exists would be corrected to become optimal very quickly indeed.
Not necessarily. There are many traits that would be advantageous that we don't posess. A spinal column that isn't so vulnerable to stress injury would be highly advantageous, but we don't have it. And that's simpler than hermaphrodism.
To offer a D&D analogy, a dedicated cleric is better at being a cleric than a wizard/cleric is, just as a dedicated wizard is better at being a wizard than the wizard/cleric is too.
Ah! But you see, what we don't know is if a dedicated wizard of cleric is better at being
a character than a multiclass. Being a better wizard isn't advantageous unless what you need is a better wizard. And, like players, nature doesn't know for sure which is better beforehand. It makes it's choice, and only finds out later. Unlike players - nature doesn't have the option of simply changing it's choice later on
I never denied that. But it's important to understand what that mixing is for - it's specifically to fight off bacteria, viruses, infection, disease, parasites and assorted other nasties that go through many generations of evolution in your gut, on your skin and between your cells in an attempt to crack the locks.
It's for a lot more than that. Avoiding the deformities of recessive genes, and increasing the availability of immunities to the population are notable, but are far from the limit of what the mixing is for.
Genes interact in strange and mysterious ways. If you don't mix them, you don't fully experiment with the material at your disposal.
. Hermaphrodites are definitely sexual - they're just not quite as good at being a male as a male is, nor at being a female as a female is.
We've never seen a true vertebrate hermaphrodite, so we cannot say what it is or is not good at. We most certainly cannot say that their non-appearance is proof, because we don't know if the experiment has ever been tried.
Perhaps Stephen Jay Gould put it best. The phrase "Survival of the fittest" is a bit of circular logic. The typical way we define fitness is by survival. That means the phrase reduces to "Survival of those who suvive," which gives us no information - speciifcally, it gives us no information on why they survived.