The Hardy-Weinberg principle is not generally found in nature because it requires certain conditions in an environment. These conditions are the absence of the things that can cause evolution. In other words, if no mechanisms of evolution are acting on a population, evolution will not occur--the gene pool frequencies will remain unchanged.
Some pregnant women experience a metallic taste in their mouth during the early stages of pregnancy, because of the hormone changes. It's also fairly common to crave certain foods, or go off certain foods, and have a heightened sense of smell.
2. Poor Oral Hygiene (Metallic or Stale Taste). With irritated gums or infections there is often low level bleeding from the gums and as the blood contains Iron (haemoglobin) this can give rise to a metallic or stale taste in your mouth. This and other dental problems are a very common cause of a metallic taste.