"a mishmash of genes from two different individuals almost always works out" => different individuals of the _same_ species (which btw is how a "species" is defined).
The evolution of organisms that gene mishmash (aka sexual reproduction) is thought to be the result of an ongoing arms race between gene sequences that "try" to stay unchanged (in higher level species) and gene sequences that "try" to "free ride" (from viruses etc.) Being able to build members of your species from "mishmash of genes from two different individuals" has the effect of scrambling the DNA of each species member which makes attack harder.
Organisms that do not do this and reproduce via cloning (aka Parthenogenesis) are often entirely wiped out once a pathogen figures out how to target their DNA -- hence the bananas types we eat change over time.
The evolution of organisms that gene mishmash (aka sexual reproduction) is thought to be the result of an ongoing arms race between gene sequences that "try" to stay unchanged (in higher level species) and gene sequences that "try" to "free ride" (from viruses etc.) Being able to build members of your species from "mishmash of genes from two different individuals" has the effect of scrambling the DNA of each species member which makes attack harder.
Organisms that do not do this and reproduce via cloning (aka Parthenogenesis) are often entirely wiped out once a pathogen figures out how to target their DNA -- hence the bananas types we eat change over time.
ps: Similar evasion is used by some computer viruses: https://www.trendmicro.com/vinfo/us/security/definition/Poly...