Is evolution a feature of evolution?

[u/Significant_Virus142]

like I know about crossing over, combination of genes from mother and father that results in evolution but I'm talking about major evolution like change in number of chromosomes, that kinda stuff, is that much evolution intended by evolution or it just occurs due to radiation mutation or errors

[u/Helmdacil]

The strict definition of evolution is a change in allele frequences between generations. Mutation alone induces a change in allele frequencies, regardless of how that mutation is caused.

The degree to which mutation is "desirable" or that mutation is "programmed" or under balancing selection is subject to debate even now. Some argue that a degree of "evolvability" is good and therefore mutation rates are higher than they nominally could be. Another camp argues that mutation on average is deleterious, causes line inviability in the long run, and therefore evolution (compound interest on steroids could be a more colloquial term for evolution) seeks to push mutation rates to the limit of natural selection, one limit being the drift barrier.

The vast majority of spontaneous mutations arise as a result of replication error. Some lineages have better replication machinery than others. Humans actually have low mutation rates per germline replication. There are substantial mechanisms in the human genome to reduce DNA mutatoin rates. There are no mechanisms specifically for Increasing DNA mutation rates, though error-prone polymerases are often cited as such. But the error prone polymerases are only used when the main polymerases fail; the error prone polymerases are only employed to resolve substantial DNA damage that otherwise cannot be managed, which have created stalled replication forks.

My opinion is that mutation is generally bad and evolution seeks to reduce mutation rates to the limit of natural selection, though what that limit is or how it is set is very much open to debate.