EggplantTrent

I understand the concept that sexual reproduction promotes more genetic variation in a population, thereby allwoing that population to adapt and go through natural selection easier (if that's the right word), but is that all there is to it? Is this the only reason why sex evolved?

EggplantTrent

IoftheBholder

In my opinion, evolution describes how but not "why"; unless you consider natural selection to be a reason.

However, I find the underlying question quite fascinating. How did sexual reproduction evolve and what selective advantages did it supply?

It part, it's interesting becaue too much genetic variation is harmful. So if sexual reproduction does introduce more genetic variation, how is it that it's not too much?

i!

AmbiguousUbiquity

I don't understand this question. Are you comparing sexual reproduction by itself, or against asexual reproduction? Or are you wondering how sexual reproduction came about? There are five major factors in having evolution occur (mutation, gene flow, genetic drift, selection, and randomness of mating) that are not necessarily needed in a population that has only asexual reproduction. As the populations got larger, it would have made no sense to continue an asexual reproduction trend.....as species were able to spread out and adapt to new, larger environments, biology kicked in at some point (I don't know when), to make it more efficient to reproduce. You can find more info on this at many ecology websites, I would imagine.

Lauren

Doubting Didymus

What do you mean by "promotes more genetic variation"? I think the biggest advantage of sex is recombination. Picture it this way (but don't try to take this as an example of how evolution actually works, because I'm going to specify a 'goal' organism for the sake of demonstration).

Suppose we have a population of ten Asexual organisms 'made' of 10 imaginary genes, creatively named 1 2 3 4, and so forth. Suppose that each of these genes has a different form it can be found in, which is an improvement over the old version. call them 1a, 2a, 3a etcetera.

in the population of asexual reproducers, (we'll assume that each generation remains the same size, and we'll give a mutation rate of 1 gene per hundred per generation, and mutations are limited to changing from 1 to 1a and so on.), the first new generation will have one lucky individual with a new beneficial gene. He might outproduce the others because of that, but within a few more generations we're bound to get a different beneficial gene in an organism that isn't descended from our first mutant. Here is where lacking recombination really fucks you over, because having been lucky enough to get two different bonus mutations, there's no way of getting them to sit in the same individual, ever. each direct lineage has to come across ALL of its beneficial mutations on its own.

The advantage of sex, in the same scenario, is that the two organisms with different bonus genes are likely to sexually reproduce, either immediately, or their ancestors down the track, just because they are both at an advantage. When that happens, theres a good chance that one of the offspring will inherit BOTH beneficial genes, and he is now at double the advantage of either of his mutant parents. Recombination means that you can horde all your beneficial mutations into the same organism, where asexual reproducers have to rely on being lucky enough to come by all their beneficial mutations independantly.

Dr.GH

Oy, Oy, Oy.

There are other advantages to sexual reproduction that the increase of genetic variation. Others, reduce genetic variation.

Let's take the very "selfish gene" position. "I, the selfish gene" am not the most fit. But I want to survive. Sexual reproduction, with a heathy dose of self fertilization, will give the opportunity to exagerate genetic diversity. This will include "I, the less fit selfish gene." Consider the recessive genes. Genetic diversity, regardless of source, is good for species survival, and this, either unchecked or severly selected, leads to species origination.

Undercurrent

An immediate advantage to sexual reproduction, for males, anyway, is that they exert a lot less effort in reproduction. Why bother carrying the full reproductive apparatus around when your environment is full of oranisms you can inject your DNA into and they'll reproduce for you at no risk to you. If everybody's doing this, you're screwed, but so long as there's a good pool of "females" it's probably an easier strategy.

And all this stuff about genetic diversity, good of the species, sure, but only as a by-product of the greedy, parasitc male breeding strategy.