2(b) Explain the concept of Hardy–Weinberg equilibrium and its relevance to the study of human populations.

Introduction

The Hardy–Weinberg equilibrium (HWE) is a foundational principle in population genetics that provides a mathematical model describing how allele and genotype frequencies remain constant from one generation to the next in the absence of evolutionary influences. It was independently formulated by G.H. Hardy (1908), an English mathematician, and Wilhelm Weinberg (1908), a German physician.

Body

1. Assumptions of Hardy–Weinberg Equilibrium

• Large Population Size – The population must be large enough to prevent random sampling errors (genetic drift).
• Random Mating – All individuals have an equal probability of mating with each other, without regard to genotype or phenotype.
• No Mutation – No new alleles should arise or be altered by mutation.
• No Migration – There should be no gene flow into or out of the population.
• No Natural Selection – All genotypes have equal survival and reproductive success.

2. Mathematical Expression

For a gene with two alleles, A and a, with frequencies p and q respectively:

These proportions remain constant if the population is in equilibrium. Any deviation indicates that one or more of the assumptions are violated, pointing to evolutionary forces at work.

3. Applications in Human Genetics and Anthropology

• Measurement of Evolutionary Change – Comparison of observed vs. expected frequencies helps identify forces such as selection or migration in human populations.
• Carrier Frequency Estimation – Used in calculating carrier rates for recessive disorders like sickle-cell anemia or cystic fibrosis.
• Population Structure Analysis – Anthropologists use deviations from HWE to infer inbreeding, genetic drift, or admixture.
• Forensic and Medical Genetics – HWE is applied to test genetic markers for Hardy–Weinberg proportions before using them in DNA fingerprinting or disease-association studies.

Contemporary Studies

“Hardy–Weinberg equilibrium provides the mathematical yardstick against which real populations can be measured to detect evolution.”

Conclusion

The Hardy–Weinberg equilibrium serves as a baseline model in genetics and anthropology. It helps quantify how evolutionary forces—mutation, selection, migration, drift, and non-random mating—affect human populations. Deviations from equilibrium indicate ongoing evolutionary change, making HWE an indispensable tool for understanding human diversity and microevolution.