- All told, sexual reproduction is weird. Given the "choice" of passing on 100% (asexual) of one's genome to the next generation or 50% (sexual), you would think that 100% (asexual) would be a more effective technique. Consequently, there must be some kind of advantage to sexual reproduction; otherwise, it's extraordinarily odd that it's so commonplace.
- One major speculation is that sexual reproduction (along with the recombination often involved in meiotic events) sort of shuffles the genome and results in a level of variation that is beneficial enough to compensate and then some for the 100 v. 50% transmission. I.e., it's a lot easier to get novel combinations when the various mutations occurring randomly in the population are routinely combined in parallel fashion, rather than waiting for a single line of asexually reproduced genomes to accumulate those same mutations serially. These variations would theoretically be key to evolutionary flexibility to changing environments.
- However, sometimes particular allelic combinations are, to whatever extent, idealized , so it would be beneficial if they were kept together. So there exists a second tension - while sexual reproduction is best at creating these sorts of beneficial allelic combinations (consisting of multiple novel mutations at multiple loci), asexual reproduction is best at maintaining a particular combination. Sexual reproduction effectively shuffles and loses those "perfect" combinations.
- This model / theory is called the "Sisyphean Model," as just like good ol' Sisyphus, sexual reproduction will push the alleles up the proverbial hill of higher fitness, only to lose that powerful combination via another sexual reproduction. And the boulder rolls back down, and sexual reproduction must begin again.
I don't really care if that makes all that much sense; the major point is that we spent four hours talking about sexual reproduction v. asexual reproduction, sans "sexual reproduction" jokes, and the whole shebang ended by discussing a metaphor based on the myth of Sisyphus. When the professor asked if anyone in the room knew why it was called "Sisyphean," I was one of two people who could give an account of the actual myth of Sisyphus. (You will recall my Camus fanboydom). I didn't know this at the time and thought I was just the only person willing to talk. So I described the myth. We're rolling along, and the major point is that this is something of a tricky situation, that clearly something MUST be going on to explain why sexual reproduction is so common, but this Sisyphean Model seems to at least partially counteract that effect. Class winds down, the professor asks if there are any questions, and after a couple seconds of silence and blank faces, I simply ask:
"So, what you're saying is that we're supposed to imagine sexual reproduction happy?*"
* - Just so we're all on the same page here, Camus rather famously ends his metaphor of Sisyphus as stand-in for the human condition by declaring that we must imagine him happy as he pushes the rock pointlessly up the hill. Defiance of his fate is his only means to maintain anything resembling individual freedom, etc. This is, imho, a fairly major 20th century philosophical quote, and someone in the room *should* have been familiar with it.
The professor - who, mind you, just described how these kinds of literary metaphors sometimes shape scientific thinking - just stared at me blankly. Mark, a classmate from my program (and the only other guy in the room, it turns out, who could have explained the myth), almost fell off his chair laughing. Everyone else: crickets.
And you know what? Screw you, roomful of academic biologists. That was GOLD JERRY GOLD, and I don't even care if you didn't get it. On three hours of sleep, I delivered a second level, perfectly-timed literary joke, and it's not my fault y'all's all ign'ant.
That is all.
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