- Population genetics is a branch of evolutionary biology that studies the distribution, frequency, and changes of genetic variation within and between populations of organisms.
- It provides the theoretical framework for understanding how evolutionary forces—such as natural selection, genetic drift, mutation, gene flow, and recombination—shape genetic diversity over time. By combining principles from genetics, statistics, and evolutionary theory, population genetics explains both the short-term dynamics of allele frequencies and the long-term patterns of adaptation, speciation, and biodiversity.
- At its core, population genetics examines the gene pool, which is the total collection of alleles present in a population. Changes in allele frequencies from one generation to the next serve as indicators of evolutionary processes at work. For example, if a beneficial mutation increases in frequency due to natural selection, it demonstrates adaptation to the environment. Conversely, random fluctuations in allele frequencies, known as genetic drift, can have profound effects in small populations, potentially leading to the loss of genetic diversity or the fixation of neutral or even harmful alleles.
- One of the foundational models in the field is the Hardy–Weinberg equilibrium, which describes the expected distribution of genotypes in a population under ideal conditions where no evolutionary forces are acting. According to this principle, allele and genotype frequencies remain constant across generations if mating is random, and if there are no mutations, migration, selection, or genetic drift. Deviations from Hardy–Weinberg expectations provide evidence that evolutionary processes are influencing the population. This model is widely used as a baseline for studying real-world populations.
- Population genetics also sheds light on the role of gene flow and migration in shaping genetic diversity. When individuals move between populations, they introduce new alleles, potentially increasing variation and reducing genetic differences between groups. On the other hand, barriers to gene flow can promote genetic divergence and eventually lead to speciation. Similarly, the accumulation of mutations over time serves as the raw material for evolution, while recombination reshuffles genetic material, creating novel combinations of alleles on which natural selection can act.
- The field has expanded significantly with the advent of molecular genetics and genomics. Advances in DNA sequencing and computational biology allow researchers to analyze entire genomes across populations, revealing fine-scale patterns of variation and adaptation. Modern population genetics informs diverse areas of science, from understanding the spread of antibiotic resistance in bacteria to reconstructing human evolutionary history and migration patterns. It also plays a key role in conservation biology by assessing genetic diversity in endangered species and guiding strategies to preserve healthy, viable populations.
