2(c) What is Mutation? Discuss its role in the process of evolution with suitable examples.

Introduction

Mutation refers to sudden, heritable changes in the structure or number of genes and chromosomes. It is a fundamental source of genetic variation and a key mechanism of evolution. The term was introduced by Hugo de Vries (1901) while studying Oenothera lamarckiana. Mutations create new alleles, which are then acted upon by natural selection, genetic drift, and other evolutionary forces.

Body

1. Types of Mutation

• Gene (Point) Mutation – A change within a single gene, such as base substitution, insertion, or deletion. Example: Sickle-cell anemia caused by substitution of valine for glutamic acid in the β-globin gene.
• Chromosomal Mutation – Changes in chromosome structure (deletion, duplication, inversion, translocation) or number (aneuploidy, polyploidy). Example: Down’s syndrome (trisomy 21).
• Somatic and Germinal Mutations – Somatic mutations affect body cells and are not inherited; germinal mutations occur in gametes and are transmitted to offspring.
• Spontaneous and Induced Mutations – Spontaneous mutations arise naturally due to replication errors; induced mutations are caused by external agents such as radiation or chemicals (mutagens).

2. Role of Mutation in Evolution

• Source of Variation – Mutations introduce novel genetic combinations, forming the raw material for natural selection.
• Microevolutionary Changes – In small populations, new mutations may become fixed by genetic drift or selection, leading to gradual evolutionary change.
• Speciation – Accumulation of genetic differences through mutation may lead to reproductive isolation and the emergence of new species.
• Adaptive Radiation – Beneficial mutations can enable species to occupy new ecological niches, as seen in Darwin’s finches or Galápagos lizards.

3. Mutation Rate and Significance

• Mutation rates are generally low (about 10⁻⁵ to 10⁻⁶ per gene per generation) but cumulative over time.
• Most mutations are neutral or harmful; a few are advantageous and form the basis of adaptation.
• In human populations, mutation studies help trace hereditary diseases, evolutionary divergence, and genetic load.

Contemporary Studies

“Mutation is the ultimate source of all genetic novelty — the spark that fuels the engine of evolution.”

Conclusion

Mutation forms the foundation of genetic diversity and evolutionary change. Though rare, its cumulative effects over generations drive the emergence of new traits and species. In human evolutionary anthropology, understanding mutation helps explain hereditary diseases, population divergence, and adaptive evolution across environments.