Sometimes, it can seem as if men and women are completely different species (at least, that’s what the trashy magazines and multitude of shitty books on relationships would have you believe). Indeed, the behavioral and hormonal differences between the two can often feel like an insurmountable gap for some.
But imagine how much tougher those whinging tits would have it if they had to contend with seven sexes, not just two.
Sound crazy? Well, it’s not crazy if you’re a protozoa. Namely, not if you are Tetrahymena thermophila, which are fairly common fresh water ciliates who just so happen to have seven different genders (conveniently named I – VII). Not only that, but our little unicellular friend also has two nuclei: a macronucleus for all its basic cellular functions, and a micronucleus dedicated to getting it on.
That’s right- their sex life is too complicated for their regular nucleus. An individual sex cannot reproduce with another of the same type (Type I can’t have little protist babies with another Type I, for example), but those 7 sexes can combined in 21 different combinations.
So yeah, it’s a little more complicated than man + woman = baby.
But what’s really interesting about these little guys is that those 7 sexes are not evenly distributed through the population. See, their sex is not determined solely by genetics (like a human’s is). Instead, their genes give them a probability of being born a certain sex- the environment is actually the determining factor (this is not a unique trait- there are many other species, including the three-lined skink lizard, that incorporate temperature and environment into sexual determination).
The sex-influencing mat gene and 13 other alleles are the influencing genetic bits. And the mat gene comes in multiple varieties, so when you really think about it, it’s no wonder the little guys need a completely separate nucleus to handle procreation.
Anyway, the alleles that allow for the possibility of multiple different gender outcomes perform better than those that only allow for one, which eventually skews the population a bit.
Seven sexes may seem like overkill, but it appears to be working for these little guys. They’re like a tiny, Earth-based version of Star Trek Species 8472 (which had 5 sexes, I believe)… only not as ugly: