When life began, reproduction was asexual. After some evolution, sexual reproduction became possible, which has, as one of its benefits, more mixing of the gene pool (strengthening the species as a whole), producing more variety and basically “helping” evolution along, as I understand it.
Anyway, how likely is it that somewhere down the evolutionary line some species may eventually have three (or more) “sexes” necessary to reproduction? Could this possibly be significantly more advantageous than requiring only two sexes to reproduce?
…ebius sig. This is a moebius sig. This is a mo…
(sig line courtesy of WallyM7)
To elaborate slightly: Trisexual reproduction adds a whole new facet to the game that it’s doubtful could ever be an advantage. While I suppose it would result in greater genetic diversity, the act of getting three seperate beings together to mate successfully isn’t something likely to happen (successful mating meaning that all three do their seperate parts to making a new creature, not just having a good time). Unless there was some major restructuring of the reproductive organs, imagine that the female had to be fertilized by the male, and then the male’s sperm had to be activated by another mating between the female and the “male-2” (for lack of a better term). This is twice as much work (if not more) for something that’s been working out well enough already with simply a male and a female.
On the other hand, m/f reproduction beats out asexual reproduction due to the mixing of genetic materials and the chance for healthier creatures to pass on their genes while the weaker ones are deprived of a chance to mate. And it’s more fun.
“I guess one person can make a difference, although most of the time they probably shouldn’t.”
Empirically, genetic algorithms gain very little, if any (depends on the application/implementation), effectiveness when the number of parents per offspring is raised above two.
Actually, just the other night I was visiting a web site that documented trisexual reproduction amongst humans. The females looked either enthralled or in pain.
A Piers Anthony book (I don’t recall the title as I read it about 15 years ago) had as one of its central themes a tri-sexual race. Here’s how it worked:
Any two of the three ‘types’ of being could be around each other with no trouble. As soon as the third type showed up all three instantly engaged in sexual reproduction. They couldn’t help themselves and there was no stopping it.
As a result the species had developed an elaborate system of pathways and what-not that ensured their were never more than two types of being present at any given time.
Presumably there were sanctioned areas where one went when one wanted to reproduce.
I think Dawn: Xenogenesis by Octavia Butler involves tri-sexual reproduction too, and has some interesting ideas on why it might be an evolutionary advantage.
Walk the Moons Road by Jim Aiken also covered the concept. The same with the TV series Alien Nation. It’s not exactly a new concept.
The best (and most hilarious) version was Ed Subitzky’s Saturday Night on Antares, the Planet with 12 Different Sexes in the National Lampoon. You think you have trouble . . . .
“What we have here is failure to communicate.” – Strother Martin, anticipating the Internet.
Ok, as much as I love sci-fi (and check out The Gods Themselves, by Asimov, btw), there are some real-world examples. There’s a species of fungus (don’t have my biology book handy, sorry) that actually has 17 known sexes. It only takes two, but any two fungi of different sex can mate.
“There are only two things that are infinite: The Universe, and human stupidity-- and I’m not sure about the Universe”
–A. Einstein
I’ve often wondered if the genetic role of the female was to preserve the genetic line, and the role of the male to introduce change. Or stated a different way, the female brings genetic stability, the male shakes things up. Look at mitochondria (sp?), which is passed down infinitely from generation to generation along maternal lines. Maybe it’'s the interplay between static and chaotic that makes for successful evolution.
In a tri-sexual species, what could be the three functions?
Ahhh, love how Piers Anthony (and Robert Heinlein for that matter) play out their Freudian fantasies (and nightmares) in their so-called legit Sci-Fi books. Free sex, forced sex, sexism, and misogyny all become legit when they’re part of an alien culture.
Peace.
And before I’m attacked by any rabid Heinlein fan, I must warn you, I read Number of the Beast – it’s stinks it does.
I could see a species evolving, where the female was impregnated twice. After the first fertilization, the egg wouldn’t be a true embryo, but a kind of meta-egg. It would take the second impregnation to form a true embryo. It’s still an embellishment on male and female, but in that scenario there would be two types of male.
Perhaps this would arise if there was a evolutionarily successful cross-species mating. Male and female of species A mate, and before much in the way of cellular differentiation happens, a male from species B mates with the pregnant female of species A. The sperm of species B invades the embryo that the female carries, and basically infects it with its genetic material, much like a retrovirus. Only this time, a successful new creature is formed. If enough of these cross-species two stage matings happen, a breeding population is formed, with the female of species A*B “expecting” to be impregnated in two stages. The first type of male would be mostly species A-like, and the second type of male would be mostly species B-like.
Wierd, but feasible, I suppose. Any geneticists out there?
