DNA absolutely hangs on to useless genotypes for some period of time. Horizontal gene transfer allows for redundant genes to exist. They have increased mutatio

DNA absolutely hangs on to useless genotypes for some period of time. Horizontal gene transfer allows for redundant genes to exist. They have increased mutation which MIGHT lead to some productive change, but for an extended period of time they don't. Not to mention biological mechanism which exist for many many generations even though they aren't used in some grow medium. The disagreement here is about time scale. If it were true that resistant phenotypes often ARE dramatically less fit to the degree you imply we could simply stop taking Antibiotics and everything would revert back to it Susceptible state. When you stop a dosage early you've very likely applying a low dosage to some subpopluation. Dosages are not linear, nor evenly applied throughout the entire population of bacteria in a human body.