Genetic Drift
Random changes in allele frequencies from one generation to the next due to chance events in reproduction. Effects are strongest in small populations where chance fluctuations are not averaged out.
Used in the Books
This term appears in 5 chapters:
"...ion (antibiotic resistance, immune evasion) provides immediate survival benefit, outweighing long-term costs (genetic load). 2. Small populations (genetic drift): In small populations, deleterious mutations accumulate due to weak selection (genetic drift overpowers selection when population size is small)."
"Book 6, Chapter 2: Genetic Drift - The Power of Randomness Introduction In the summer of 1977, a massive drought struck the Galápagos island of Daphne Major."
"The mathematical relationship is straightforward: even a small amount of migration (one successful migrant per generation) can overpower genetic drift (random changes in gene frequencies) in populations of moderate size, while very high migration rates can swamp local selection, preventing populatio..."
"The process is historical and contingent - small changes in initial conditions can lead to radically different outcomes (see genetic drift, Chapter 2). Yet certain solutions are strongly favored when organisms face similar selection pressures."
"Smaller population experiences stronger demographic stochasticity (random bad years crash the population further). 5. Genetic diversity declines (genetic drift, Chapter 2), reducing evolutionary potential to adapt to threats. 6. Population falls below Allee threshold, where individuals can't find mates or co..."
Biological Context
In small populations, alleles can be lost or fixed purely by chance, regardless of their fitness effects. Genetic drift reduces genetic diversity and can cause populations to diverge randomly. Combined with founder effects, it explains why isolated island populations often differ markedly from mainland ancestors.
Business Application
Small organizations experience 'cultural drift'—random fixation of practices that happened to be present in early employees, regardless of whether they're optimal.