Say you are a single celled organism. To reproduce you have to double your size and then you need to split yourself in half. Repeat indefinitely.
Now say you are a single celled organism that has the option to reproduce sexually. To reproduce you need to increase yourself to 3/2 your original size and find a similar mate. Then you both contribute 1/2 to the new organism and repeat indefinitely.
Asexual reproduction requires you to double in size; sexual reproduction requires only a 3/2 increase. Therefore the turn-around time for sexual reproduction is inherently shorter than for asexual reproduction (assuming there are viable mates readily available).
Is there a selective benefit to a shorter turn around time for reproduction? If the species must constantly be adapting to a changing environment (that would be everyone), then having a higher rate at which new mutations (and thence adaptations) are introduced into the population is critical.
Secondly, given that there is enough food but it takes time to collect, I count more offspring for sexual reproduction:
In sexual reproduction, there is an additional child from the first generation of children (as compared to asexual splitting) created in the same amount of time: At the +50% mark #1 & #2 mate to create #5, and #3 & #4 mate to create #6. Then, at the 100% mark (or plus an additional 50%) #1 & #2 mate to create #7, #3 & #4 mate to create #8, and, at the same time, the initial children #5 & #6 mate to create #9. #9 is also one generation ahead of the offspring of asexual replication.
Now, to be honest, I’m confused. I don’t think that anything above is particularly complicated. However, Wikipedia does not note this as a benefit of sexual reproduction. It actually says that asexual reproduction is much faster. This makes me think that I must have made a mistake or else someone would have added it.
The going theory appears to be that since every organism in an asexually reproducing species can give off children, then there is twice the potential for offspring. This completely ignores any struggle that an organism might have that would prevent it from reproducing, or that work can be split with a mate making it easier to reproduce.
My main assumptions are, among others, that there already is a significant population of organisms, the organisms are not too fussy about their mates (no significant waste of energy searching for a mate), energy / work is being split with the mate, and that the limiting factor has to do with gathering food. I can’t see how, if these (reasonable?) assumptions hold, sexual reproduction isn’t the dominant, winning strategy.