Genetic technologies will allow doctors to know who may get that side effect and should therefore not take a drug. Like the slide rules disappeared, so will our current medical technology as the information from the genome project becomes exploited. That might explain why we have more than 200 genes that we seem to have inherited from a variety of different bacterial species. A trip back in evolutionary history could help explain how it happened. Bacteria have lived on the planet for some 3 billion years, while the upstarts, humans, came along less than 200,000 years ago.
Bacteria are among the most primitive life forms on earth.
When our proto-human ancestors first met bacteria, they learned to live together. Bacteria help us with digesting food, for example. Early on during this shared living arrangement, scientists theorize the different species of bacteria transfered their DNA to our sex cells, the egg and sperm. DNA from the micrboes somehow got into the blood stream and found its way to these sex cells. Lo and behold, they still show up in our genes.