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.
All the above medications have side effects that include producing metallic taste in mouth. Oral problems like periodontitis and gingivitis can also cause this taste. It can be the symptom or warning sign for underlying disease like cancer, ulcer, food allergy and lichen planus. Many kinds of poisoning like lead poison, mercury poison, iodine poison, cadmium poison, selenium toxicity, increased copper level can produce metallic taste in your mouth.