VAID'S ICS – Best UPSC Anthropology Coaching in Delhi Since 1985

Comprehensive Classroom Course · Admissions openRegister now
+91 93113 37737
  • +91-93113 37737, +91-99999 46748
  • 73(FF), Old Rajender Nagar Market, Delhi - 110060
  • MON to SUN 9.00 am - 6.00 pm
Facebook Youtube Instagram
Menu
Enquire Now
Home/Anthropology/Mains PYQ/2021/Paper I/Human Genetics & Human Biology
UPSC MainsAnthropology Optional Paper I 2021 15 Marks Model Answer Available

Genetic Mechanisms of Micro and Macro Evolution — 2021 Paper I

Question · 2021 · Paper I · 15 Marks

Explain the genetic mechanisms of micro and macro evolution.

Model Answer

VAID ICS

Approach

  • Demand of Question: Explain the genetic processes responsible for evolutionary change within populations and above the species level.
  • Structuring the Response: Define micro- and macroevolution → mechanisms of each → show their continuity through speciation.
  • Key Dimensions to Cover: Mutation, recombination, selection, drift, gene flow, reproductive isolation, chromosomal changes and speciation.

Model Answer

Introduction

Microevolution refers to changes in allele frequencies within populations across generations, whereas macroevolution concerns evolutionary change at and above the species level, especially speciation and lineage diversification. The Modern Synthetic Theory, developed through Fisher, Haldane, Wright, Dobzhansky and Mayr, connected Mendelian genetics with Darwinian natural selection. Sewall Wright’s “Evolution in Mendelian Populations” (1931) formally analysed mutation, migration, selection and random genetic drift as forces changing gene frequencies.

Genetic Mechanisms of Microevolution

  • Mutation: Gene and chromosomal mutations create new alleles, providing the primary source of novel hereditary variation.
  • Recombination: Crossing-over, independent assortment and random fertilisation produce new combinations of existing alleles, increasing variation on which selection acts.
  • Natural selection: Differential survival and reproduction alter allele frequencies through directional, stabilising or disruptive selection.
  • Genetic drift: Random fluctuations alter allele frequencies, especially in small populations. Founder effect and population bottlenecks may rapidly reduce or restructure genetic diversity.
  • Gene flow: Migration introduces or removes alleles between populations; it usually reduces differentiation, although restricted gene flow permits divergence.

Thus:

Mutation + Recombination → Variation → Selection/Drift + Gene Flow → Change in allele frequencies

Modern population genetics continues to recognise mutation, gene flow, genetic drift and selection as the principal microevolutionary forces.

Genetic Mechanisms of Macroevolution

Macroevolution does not require an entirely separate genetic machinery; population-level changes become macroevolutionary when they generate reproductive isolation, speciation and persistent lineage divergence.

Reproductive isolation: Divergent populations accumulate genetic differences producing pre-zygotic or post-zygotic barriers. Dobzhansky, in Genetics and the Origin of Species (1937), placed genetic divergence at the centre of species formation. Modern speciation genetics similarly defines speciation fundamentally through the evolution of reproductive isolation.

Divergent selection and drift: Geographical or ecological isolation permits populations to diverge through different selection pressures and stochastic changes.

Genetic incompatibilities: Mutations accumulating separately in populations may interact negatively in hybrids—the Dobzhansky–Muller incompatibility principle—producing sterility or inviability.

Chromosomal evolution: Inversions, translocations, fusions, fissions and duplications can suppress recombination, reduce gene flow or lower hybrid fertility, thereby facilitating reproductive isolation.

Gene duplication and regulatory changes: Duplicated genes can acquire new functions, while alterations in developmental and regulatory pathways may generate major morphological innovations.

Micro–Macro Evolutionary Continuity

Variation → Population divergence → Reproductive isolation → Speciation → Adaptive radiation

G.G. Simpson, in Tempo and Mode in Evolution (1944), integrated population genetics with palaeontology and argued that large-scale evolutionary patterns could largely be interpreted through processes operating within populations over geological time.

Conclusion

Thus, microevolution supplies genetic variation and alters its distribution, while macroevolution represents the long-term consequences of these processes when divergence becomes reproductively and phylogenetically established. Speciation therefore forms the crucial bridge between population-level genetic change and large-scale evolutionary diversification.

2026 How would you find out that a particular disease/disorder is inherited and, if so, in which manner? Elaborate with suitable examples. 2026 What do you understand by fertility and mortality? How are these influenced by biological and socio-ecological factors? 2026 In what manner is our understanding of serogenetics and cytogenetics useful in reproductive biology? What are the major ethical issues involved in reproductive technology? 2026 Why the classifications of Indian populations, based on somatometric and somatoscopic characteristics failed to develop a common understanding of the population diversity?

Want feedback on your answer?

Join the Anthropology workshop or get structured answer-writing guidance from VAID ICS.

Join Workshop Contact VAID ICS

UPSC Anthropology Optional 2021 — Paper I

28 questions

1(a) Animism and Deep Ecology

10 Marks150 words
Syllabus: Paper I > 5. Religion > Forms of religion > Animism
2021Paper IAnthropology of ReligionModel answer available

5(d) Descent Groups

10 Marks150 words
Syllabus: Paper I > 2.5 Kinship > Descent groups
2021Paper IKinshipModel answer available

5(a) Human adolescent growth spurt

10 Marks150 words
Syllabus: Paper I > 10. Human growth and development > Stages of growth > Adolescence
2021Paper IHuman Genetics & Human BiologyModel answer available

5(e) Modes of Subsistence

10 Marks150 words
Syllabus: Paper I > 3. Economic Organization > Modes of subsistence
2021Paper IEconomic & Political AnthropologyModel answer available

5(b) The losses and gains of erect posture

10 Marks150 words
Syllabus: Paper I > 1.5 Characteristics of Primates > Skeletal changes due to erect posture
2021Paper IHuman Evolution & PrimatologyModel answer available

1(e) Thermoluminescence (TL) dating

10 Marks150 words
Syllabus: Paper I > 1.8(a) Chronology: relative and absolute dating methods
2021Paper IPrehistoric ArchaeologyModel answer available