How does human evolution or natural selection related to the susceptibility of disease?

due to the pollution and the evolution by men, the cells in our bodies must lose something in order to get something better, in this case, our ability to avoid cancers, diseases. and sicknesses is lost, but we have evolved into even more intelligent species, thus called HOMO SAPIANS

what have scientists found to be the most efficient and effective way to insert new sequences into an individual? a-scientists have created genetically altered foods that release dna during digestion. b-scientists use viruses to insert specific gene sequences. c-scientists irradiate genes so that they can be absorbed through the skin.