Why Genetic Variation Matters

Scientists think genetic variation may be a natural safeguard for a species, because such variation increases the likelihood that individuals will respond differently to most threats that arise. For example, a disease may be deadly to most members of a population, but if a few individuals are genetically different enough to survive it, the species will live on.

Genetic variation may also help guard against the disorders caused by inheriting flawed genes. Generally speaking, organisms inherit two copies of each gene, one from each parent. In human beings and other animal species, most inherited diseases occur only if an individual inherits a flawed version of the same gene from both parents. In a population with a great deal of genetic variation among its members, the odds of both parents having the same flawed gene are low. But in a population without much variation, it may be highly likely that both parents will have the same versions of genes. In such a group, many offspring may be born with inherited disorders.