Mutations may be beneficial, neutral or deleterious (bad) for the organism. Around 95% of mutations have no significant immediate effect or are neutral, and most remaining ones are deleterious.<ref>http://www.cs.unc.edu/~plaisted/ce/genetics.html</ref><ref>http://www.talkorigins.org/faqs/mutations.html#Q1</ref> Mutations are unavoidable and they are necessary for evolution to work at all. Natural and [[sexual selection]] decide which phenotypes will be prevalent in future generations and which mutations will become fixed (meaning highly prevalent in the gene pool).
Older parents produce more
mutated offspring.<ref>https://www.bionews.org.uk/page_96182</ref> There is also evidence that the mutation rate is much higher in human males (up to 6 times higher), which has also been found in other species such as birds.<ref>https://www.ncbi.nlm.nih.gov/pubmed/10978293</ref><ref>https://www.sciencedirect.com/science/article/pii/S0959437X02003544?via%3Dihub</ref> This has lead to a hypothesis of evolution being largely driven by mutations in the male germline. This finding is heavily contested however.
== Kinds of mutations that can occur ==