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Home/Anthropology/Mains PYQ/2014/Paper I/Human Genetics & Human Biology
UPSC MainsAnthropology Optional Paper I 2014 20 Marks Model Answer Available

Ageing and Senescence — 2014 Paper I

Question · 2014 · Paper I · 20 Marks

Discuss Ageing and Senescence. Describe either the biological or social theories of Ageing.

Model Answer

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Approach

  • Demand of Question: Explain ageing and senescence and describe one major set of theories explaining the ageing process.
  • Structuring the Response: Define both concepts, distinguish them, then discuss major biological theories of ageing with their strengths and limitations.
  • Key Dimensions to Cover: Ageing, senescence, programmed theories, cellular ageing, free radicals, telomeres, wear-and-tear and evolutionary perspective.

Model Answer

Introduction: Ageing is the progressive sequence of biological, psychological and social changes occurring with increasing chronological age. Senescence refers more specifically to the age-related decline in physiological efficiency, repair capacity and functional reserve.

Thus:

Ageing = Broad life-course process
Senescence = Progressive biological deterioration

Features of ageing and senescence

Common biological changes include:

  • reduced muscle mass and strength;
  • decline in bone density;
  • reduced cardiovascular efficiency;
  • diminished immune response;
  • slower tissue repair;
  • sensory decline;
  • reduced reproductive function.

Ageing is highly variable and is influenced by:

Genes + Environment + Nutrition + Lifestyle + Disease

Biological theories of ageing

  1. Programmed ageing theory

This approach proposes that ageing is partly regulated through genetically controlled biological programmes.

Age-related changes in:

  • endocrine activity;
  • cellular regulation;
  • gene expression

may progressively reduce physiological efficiency.

  1. Cellular senescence and Hayflick limit

Leonard Hayflick demonstrated that normal human somatic cells have a limited number of divisions.

After repeated replication:

Cell division → Replicative limit → Cellular senescence

This challenged the belief that cultured normal cells divide indefinitely.

  1. Telomere theory

Telomeres protect chromosome ends but shorten during repeated cell division.

Thus:

Repeated cell division → Telomere shortening → Replicative senescence

Telomere shortening is therefore associated with cellular ageing, although ageing cannot be explained by telomeres alone.

  1. Free-radical theory

Proposed by Denham Harman, this theory argues that reactive oxygen species generated during metabolism damage:

  • DNA;
  • proteins;
  • lipids;
  • cellular membranes.

Accumulated oxidative damage contributes to declining cellular function.

  1. Wear-and-tear theory

According to this view, tissues deteriorate because of accumulated damage resulting from:

  • metabolic activity;
  • environmental exposure;
  • mechanical stress.

However, organisms possess substantial repair mechanisms, so simple mechanical “wearing out” is insufficient as a complete explanation.

  1. Somatic mutation theory

Mutations and damage accumulating in somatic cells may impair cellular functions over time.

This may contribute to:

  • tissue dysfunction;
  • cancer;
  • age-related degeneration.
  1. Immunological theory

With increasing age, the immune system undergoes immunosenescence.

This may produce:

  • reduced resistance to infections;
  • weaker vaccine responses;
  • altered immune regulation.
  1. Evolutionary theories

Evolutionary explanations argue that natural selection becomes less effective against harmful effects expressed after reproduction.

Important ideas include:

  • Mutation accumulation — late-acting harmful mutations may persist;
  • Antagonistic pleiotropy — genes beneficial early in life may have harmful later-life effects;
  • Disposable soma theory — organisms allocate limited energy between reproduction and bodily maintenance.

Thus:

Reproductive investment ↔ Somatic maintenance

Critical assessment

No single theory explains all aspects of ageing.

Ageing is better understood as an interaction of:

Genetic regulation + Cellular damage + Environmental exposure + Evolutionary trade-offs

Chronological age therefore does not correspond perfectly with biological age.

Conclusion

Ageing is a multidimensional process, while senescence denotes the progressive decline in biological functioning associated with later life. Biological theories such as cellular senescence, telomere shortening, oxidative damage and evolutionary trade-offs show that ageing results from multiple interacting mechanisms rather than a single cause.

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? 2026 Canalization and catch-up growth. 2026 Genetic polymorphism and natural selection.

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