Is it possible that there could be more than two sexes in an alien species?

Yes it could be perfectly possible. Many things could be possible when it comes to life on other planets that we would find very strange. For example all life on Earth is carbon based, but there's nothing to say that on another planet it couldn't be nitrogen or oxygen, or even something bizarre like chlorine or mercury based.....

As far as how it could work: humans are diploid organisms, meaning we have 2 full sets of chromosomes; 2 copies of each one. However, there are some species even here that can be triploid or tetraploid organisms. Usually it isn't natural and the organism cannot reproduce or may not be able to survive, but sometimes, especially in plants, they can have desirable traits. For example, grass carp are common in some ponds to keep it clean of weeds, but they aren't pretty fish so you don't want them to reproduce and take over. You can get grass carp with 3 sets of chromosomes (triploid) and that makes them sterile so they can't reproduce. Seedless fruits are another example.
Anyway, in humans since we have 46 chromosomes, or 2 copies of all 23 different chromosomes, our sex cells have to have half the number of a normal human. They go through meiosis and come out with 23 chromosomes. Then they combine to give you a 46 chromosomed human.

Point being, there could be an alien species that has to have 3 or more sets of all chromosomes (assuming they have chromosomes or DNA at all). Their reproduction could work essentially the same as ours somehow, and require 3 parents. Each of the parent's sex cells would have 1/3 the total number they need to reproduce, so when the 3 come together it forms a viable alien fetus.


Just a thought. Hope that satisfies you. That's a very interesting question, and I think it is totally possible. Maybe not likely, but who knows.

Of course, if we want to speculate that their are aliens, whose to say whether or not there might be more than 2 sexes.

I read in a scifi novel once where there was some organism that had 3 sexes... 2 supplied genetic material to the 3rd, which incubated the progeny and may or may not have contributed genetic material... so who knows... it's not impossible.

If more than two gametes fused to form a zygote, you could have one sex per gamete needed.  There are single celled organisms, particularly fungi, in which there are numerous mating types, gametes which can fuse with any type other than the same type.  All animals, even sponges, form heterogametes, one large (ovum), one small (sperm, even if not flagellated).  That is what defines two sexes, even in hermaphrodites.  The mechanics of reproduction are immensely varied on that theme, such as sea horses where the males carry the young.  Freed of the constraints of Earth's natural history and able to construct one of your own, anything is possible.

The Pierson's Puppeteers from Larry Niven's "Known Space" stories had a pseudo-three-sex configuartion.  A separate species which reproduced independently was the third sex--not so far off from flowers which require another species to pollinate them.

On earth there are a number of organisms that have more that two sexes. So if there is life on other plants, there is no reseon that it too could not have multiple sexes also.

If there is life with  a complex body structure (multi-celled with organs) on other plants, chemically it is most likely if not necessary that it would be organic based, and two sexes would be the most efficient means to produce genetic diversity by means of sexual reproduction. The entire purpose of sexuality is genetic diversity, multi-sexes would ensure the greatest diversity but also could be a limiting condition in mate selection.

On Saturn the sexes are three
which is awkward I think you'll agree
for performing con brio
you must have a trio
and it even takes two for a pee

(Attributed to "Dr. A" Isaac Asimov)

Hell yeah that is possible!

First of all, as stated by ogyno84, that already happens here!

Check out this article for one example:

http://www.newscientist.com/article/dn20191-zoologger-the-hairy-beast-with-seven-fuzzy-sexes.html#.Uifsk2RC4yc



What if an alien civilzation were more like some insects that we have on Earth? Like bees?

Some are born to be essentially genderless and have no reproductive role whatsoever, while others are born with the sole purpose of procreating.

The purpose of a differentiation between genders is the need to exchange the encoding material necessary for life (i.e. what is DNA for us.)

That just means that two is the minimum for gender differentiation, right?