Genetic drift
Genetic drift is change in allele frequencies caused by sampling error rather than by any difference in fitness. Each generation is a finite sample of the one before it, so frequencies wander even when no variant is favoured, and a variant can be lost or fixed by chance alone. The effect is stronger the smaller the population, which is why isolated and recently founded populations diverge fastest.
Why it matters
It is the null process selection has to be measured against; a frequency change is not evidence of adaptation until drift has been ruled out.
Also written: drift
Where it comes up
Read about Genetic drift on Wikipedia
Sources
- Genetic drift Wikipedia
- Genetic Drift and Effective Population Size Nature Education Scitable
- Population Genetics Stanford Encyclopedia of Philosophy
