Genetic Variation

    Question: Selection is often assumed to eliminate genetic variation. So, why is genetic variation then not eroded over time? 

Well, what is genetic variation and why is it important? Genetic variation is just as it sounds, it is the diverse variation and combinations of alleles in a population's genome. Genetic variation is important because without it there would be no changes in our genes. We wouldn't improve as natural selection cannot happen without variation in our genes. Variation in our genetics in a population is what gets us through diseases and environmental impacts. Loss of genetic variation especially in small populations results in lower reproductive fitness, performance, and thus increases extinction chance. Genetic variation improves the "fates" of individuals and populations because heterozygotes tend to do better than homozygotes because more alleles allows for more solutions to environmental challenges. 

I believe in some situations genetic variation can be eroded due to inbreeding. Continuous inbreeding increases the rates of recessive alleles which would reduce variation over time. This is an issue especially in smaller populations. In smaller populations, everything is amplified. 

When inbreeding is not taking place, genetic variation is not eroded over time due to random mutations and immigration can increase genetic variation. A common tactic used to conserve a population of individuals is bringing in other individuals of the same species but of a different population. This situation would increase genetic variation thus decreasing extinction risk.