Is sex important?

Sex is not important. While there are benefits to sex, there are more benefits to asexual reproduction, or cloning. With enough luck in mutations and through travelling, asexually reproducing species such as the bdelloid rotifer can reap all the benefits of asexual reproduction while avoiding the repercussions.

Organisms that engage in sexual reproduction have, on average, lived longer than those who do not. This is due to the fact that sexually reproducing organisms do not rely only on mutations, which can be harmful. Also, sexually reproducing organisms are less vulnerable to disease, as they have different DNA, which will make it harder for disease to spread.

However, sex requires a lot of effort. As Olivia Judson explains in her book, Dr. Tatiana's Sex Advice to All Creation, "a male flower who wishes to be a Lothario and have his pollen strewn to as many mates as possible must seduce not female flowers but bees... other creatures must wear gaudy costumes, be they fancy feathers or frivolous fins; they must sing and dance for hours and hours; they must perform prodigious feats, building and rebuilding nests and bowers" (2).

Finding a mate requires an enormous amount of energy, and is rather inefficient. There are many flaws to the process, too. Even if there is an organism with a trait that would revolutionize the species, if that organism cannot have sex, the trait will die with them, and the species will never be able to benefit from the organism's trait. Also, sex may interfere with survival. Traits that attract mates are bold so that they can be seen by possible mates, but those traits can also be seen by predators, making them easier prey. Finally, organisms that reproduce sexually must compete with others of their species for mates, as it often takes a while for organisms to decide who to mate with.

Asexual reproduction, however, is much more efficient. Organisms that reproduce asexually have no need to expend large amounts of energy in order to find a mate. Also, asexually reproducing organisms have twice as many offspring as sexually reproducing organisms. "If females [of a sexually reproducing species] have fewer than two children, the population shrinks; more than two, and the population grows," says Judson. "In an asexual population, however, each female needs to have only one child for the population to remain the same size. More than one, and the population will grow" (215).

On the flip side, organisms that engage in asexual reproduction usually die out after a short amount of time either because of harmful mutations or viruses. According to Muller's ratchet, one of the theories attempting to explain why species that reproduce asexually tend to die out quickly, asexually reproducing populations die out because the number of harmful mutations will inevitably grow. Kondrashov's hatchet, another one of these theories, disagrees. It says that each individual can hold some amount of slightly harmful mutations until they die. Because sexually reproducing populations shuffle genes, the unlucky organisms with too many harmful mutations die. However, in asexually reproducing populations, many organisms will die due to bad mutations, as their only way to change their genes is mutation. Because asexually reproducing organisms mostly have the same genes as each other, it is easy for them to be killed by viruses. This is known as the Red Queen.

Something that confused me was Muller's ratchet and Kondrashov's hatchet. They both seem to have the same point. Also, why does Muller's ratchet need assumptions to be met when Kondrashov's hatchet does not? I want to learn about how scientists found out that there are two different types of reproduction, and if it's possible to control mutations.