Summary: Why do some nations prosper, while other languish? North and South Korea from space. Source: NASA A common way for medical researchers to differentiate between genetic and environmental factors is to study identical twins. Identical twins share the same genes, so the effects of different factors can be evaluated. For example, scientists examined 79 pairs of adult identical twins where one twin had smoked at least five years longer than the other. They found that the smokers […]
