Just found "male:female ratio" in the sources. Not sure about that. The world of genders is not binary!
Means the ratio between registered male and registered female members. Example: 10 registered males, 5 registered females. Ratio: 2:1.
And declared; that's important. For understandable reasons, many women don't just give out that information and prefer to stay under the tallywacker radar.
I'm not sure what the ratio information's purpose is, as it's obvious you'll probably get a high ratio on female-oriented forums, but maybe for a first-time visitor, it's something nice to know. (Especially if you're a woman, again... ;))
I think the OP meant that Elk should add support for Alien genders, though :D Or maybe, replace "Gender" with "Current gender" or "Chosen gender"...
Well, I suppose the ratio was added (at the time of... SMF 1.0?) because it was possible.
Maybe the gender could simply be "moved" to a custom profile field and let people handle it the way they want. ;)