Can there be three genders or more

[thunkit]

I have mostly seen that during evolution the amount of gender increased that is Assexual basic unicelluar animals,then came hermaphrodites then bisexual and also i have seen that the more the amount of gender the more intelligent they are in general
is there a possibility of having more genders in the future evolution?

 

[nobahar]

Hi Thunkit.
I don't see what other genders you could have.

 

[Eslocklier]

I don't either. "bisexual" and "hermaphrodite" are not genders. One is a sexuality, the other is a phenomenon.

 

[cesiumfrog]

Aren't there microorganisms with dozens of genders?

 

[nobahar]

Aren't there microorganisms with dozens of genders?

What do you mean?
Male/Female or some 'variation' thereof -such as Hemaphroditism (with its own variations) - is all I am familiar with. Essentially, they are all based on just a male/female theme. (Or no gender.)

 

[cesiumfrog]

What's to stop there from being three distinct classes of individual, which are each fertile in combination with other classes and infertile in combination with other individuals of the same class?

 

[bobze]

There are shrimp, ants and a few other species that have "multiple" sexes. In the case of the shrimp they have chromosomes ZZ, ZW, WW (male, female and hermaphroditic female, who can self fertilize, if memory serves correct).

There is also another species of shrimp I believe who's sex is determined by certain genes, not chromosomes and can again have 3 "sexes". From an evolutionary standpoint there is lots of reasons that only 2 sexes stayed with most of the animal kingdom. Most of which probably have to do with the way that resource utilization occurs for the production of gametes and the fact that once a good system for introduction of variation was hit upon, it stayed.

There are other problems as well, like the http://www.indiana.edu/~curtweb/Research/cost%20of%20males.html" . As males hinder a populations ability to grow and a individual to get it's genotype into the next generation, the evolutionary benefit of sex decreases.

Which tells us there is something else going on. When we observe species which cycle through asexual and sexual reproduction, we notice that they favor sexual reproduction during times of environmental instability--Producing more varied offspring who are more likely to "hit" upon a novel permutation of variation and be more successful in the later environments.

Adding another "sex" to such a system would make the "cost of sex" become a 4 fold cost, instead of a "2 fold cost".

If you want to learn about it, I'd suggest John Maynard Smith's The Evolution of sex, as that is still pretty much the primer on "why sex". That would also prepare you to understand more eloquent ideas about the evolution of sex.

 

[nobahar]

Surely, you still have only a male/female distinction. The individual in question would simply be male or female with respect to another individual.

E.g.(Where -> denotes DNA transfer from one individual to another.)
A -> B -> C <-A
This would make C a female. A a male. B a male with respect to C and a female with respect to A. So the gender definition just has to be considered relatively.

 

[bobze]

The problem is, methinks, is in defining sex. Like so many things in biology, there isn't an all inclusive definition that pertains to all life forms.

If we take the approach of reduction and say that "sex" is the necessary and sufficient number of variant types needed to maintain population growth (go back to the picture I put in, in the above post)-Then indeed we can have more than one sex.

The ants can have at least 3. Where there is the female sex (the queen) and 2 'male' sexes. One 'male' sex is capable of fathering only workers, while the other is capable of fathering only other queens.

Without all three the population would collapse. There is even a potential "fourth sex" for some of these populations because of line-hybridization with queens from similar, yet distinct species.

The terms "male" and "female" we apply to mammals creates a dichotomy not necessarily applicable to all other organisms on earth.

Again, it gets really complicated when we get outside the paradigm of humans or mammals. Imposing definitions on nature is a quick way to play the fool. When we create a definition for nature and nature disagrees the definition changes. We have to be mindful of that. Its similar to a caveat our gross anatomy teacher offered us on our first day of gross anatomy. "The cadaver is always right".