I think that sexual reproduction has 5 benefits.
1)it bans selfishness by forcing you to spend time with others. it forces sociality onto you. if there was no sex, you would have no reason to interact with anyone. you could just eat grass, and then there could be two you’s. cells just eat each other. but since animals are sexual, they form groups. species that are less forced into forming groups, are less likely to form groups, and because of that, they may be defeated by another species that did formed larger packs.
2)by banning cloning, it ensures that some amount of genetic diversity would always persist, and it would act as a buffer against environmental changes. you can’t generate mutations when you need them. it has to be already there. for example, humans turned the banana plant into an asexual species because they didnt want seeds inside the fruits. then a pathogen arised, and killed all the bananas. and humans were forced to take the wild varient of banana, and domesticate it from scratch. if they kept it sexual, only some of them would be killed by the pathogen, others would be more resistant because of their different genes. if you don’t entirely ban the ability to clone, everyone would clone themselves because their clones would look more similar to them than their sexual offsprings. and so there would be no diversity, and extinction would happen at the first instance that the environment changes.
3)it allows multiple traits to be selected at the same time. in an asexual species, when a beneficial mutation happens to someone, for that mutation to spread to the whole population, that individual has to clone itself and become the whole population. if there are two individuals that had a beneficial mutation, sorry, you have to choose only one. the one with the best mutation would defeat everyone, including the other other ones that have good mutations. without sex, mutations have to be collected serially, one after the other. sex makes it so that you can collect mutations in parallel. genes can expand within a population without their hosts needing to expand. if a gene gives 10% advantage or 1% advantage to its hosts, it can get selected. genes get tested again and again in different combinations with each other. good ones slide past each other, without butting heads. and bad ones are surgically removed without being forever tied to the rest of the genome.
if we try to model this with math, the speed at which new mutations arise is equal to the population size, times mutation likelyhood per birth, divided by time between each generation, so, either divided by period or multiplied by frequency
m = p * l * f
if you have sexual reproduction, when a good mutation happens, it is guarenteed to stay. so the speed at gaining good mutations is the same as the speed of good mutations happening
but if you have asexual reproduction, after a good mutation happens, you have to wait until it becomes dominant, before you can get the next good mutations. if we say that the speed a cell expands to the whole population is proportional to logarithm of the size of the population (since the cell multiplies exponentially)
m = l * f * p / log(p)
in both sexual and asexual reproduction, larger population size means faster evolution. since limit(x/(x/log x)) as x goes to infinity aproaches infinity, we can say that, evolution speed of a sexually reproducing species becomes infinitely faster than the evolution speed of an asexually reproducing species of the same size as population sizes increase.
4)it prevents the species from fragmenting into lots of other species, by maintaining gene flow between different populations. so it not only makes evolution faster in larger population sizes, it also does make your population size higher.
imagine that you have a rock on the forest floor. the bottom of the rock and the top of the rock would have different conditions. so different species of bacteria would grow in those patches. now imagine that the forest has a desert next to it. the forest has forest foxes living in it, and the desert has desert foxes. a mutation can happen in desert foxes that would be beneficial to forest foxes but not desert foxes. that mutation can linger in desert foxes for some time, before finding its way to forest foxes, where it quickly starts spreading. so you can pull mutations from a very wide region, not just your immediate surroundings. if the foxes were asexual, a mutant forest fox would only expand into the forest, and a mutant desert fox clones would only expand in the desert. they would be hyper specialised to their habitats. they wouldnt be generalist, because there would be no beneficial to being a generalist. you cant pull mutations from a wide region, if you disabled gene flow. and as you know, generalist species are more likely to survive extinction events than specialist species. the only way for desert fox clones to expand into the forest, is for that desert fox specimen to have an advantage that would cause it take everywhere, which is very unlikely when the forest fox can have forest specific adaptations. so if there were two species in the forest both competing for the same niche, one asexual and one sexual, the sexual species would defeat the other and take the niche, because it can pull genes from a wider region, there are no climate barriers in between, it is less likely to act as barrier.
5)if there is no sex, there wouldnt be polygamy. polygamy (sexual selection) is another thing that can cause evolution. only flying birds and humans have somewhat monogamy, because they have to look after their children for a long time and they decided to use their males for that. in all other species, males are not useful for the species, they fight each other and then they are discarded. there was a fish experiment where when the natural selection was high, the fishes evolved camouflage, but when the natural selection was removed, they evolved colorful pigmentation in order to attract attention and secure mates. so sexual selection can reduce the natural fitness of a species. such as a peacocks tail. maybe in some instances it can also increase. maybe there is instrumental convergence. but i cant think of any such instances. typically it is the herbivores that have horns and they ram into each other during the mating season. and they are not putting up a good fight against the carnivores. they arent becoming carnivores themselves and forcing the other species to become a herbivore. i am also unsure if that is how success would be measured.