Eli5: We have a dna correction system to avoid variations, but, sexual reproduction to promote variations. So, Are variations good?
In: Biology
We want *non-harmful* variations. Variation is good as long as it doesn’t result in harm, because it makes a population more resilient. The problem is that most random mutations are harmful, because you’re far more likely to break a thing by jumbling it up than randomly improving it.
With sexual reproduction though, the variation you’re adding to your lineage isn’t random. Even on the most basic level you can guarantee that your partner’s DNA is capable of surviving to adulthood. And most organisms have some form of additional selection process to increase their chances of breeding with the partners that have the most successful genes they can.
An additional consideration is that you *really* don’t want cells that are already part of your body to start mutating. If your gametes have a bad mutation, most of the time the embryo will just die before it matures, and you can make a new one. But if your somatic cells mutate, there’s a good chance of them becoming cancerous, and that can kill you. So for multicellular organisms there’s a strong benefit to resist mutation in general.
The exception for this are microbes like bacteria and viruses. Microorganisms reproduce quickly and don’t have to worry about cancer, so sacrificing one out of a hundred cells to experiment on the off-chance they stumble upon a good mutation is a worthwhile gamble. So they typically have far weaker DNA correction systems than multicellular organisms.
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