6(a) What is acclimatization ? Discuss adaptive responses to high altitude and cold climate.
20 Marks
Syllabus: Paper I > 9.7 Man's physiological responses to environmental stresses
Physiological and Evolutionary Theories of Aging — 2021 Paper I
Question · 2021 · Paper I · 15 Marks
Discuss the physiological and evolutionary theories of aging.
Model Answer
VAID ICSApproach
- Demand of Question: Explain major proximate/physiological mechanisms of aging and evolutionary explanations for why senescence persists.
- Structuring the Response: Define aging → physiological theories → evolutionary theories → synthesis.
- Key Dimensions to Cover: Free radicals, somatic mutations, cellular senescence, neuroendocrine/immunological decline; Medawar, Williams and Kirkwood.
Model Answer
Introduction
Aging or senescence is the progressive decline in physiological function and reproductive fitness with advancing age. Theories of aging can broadly be divided into physiological/mechanistic theories, explaining how deterioration occurs, and evolutionary theories, explaining why natural selection has not eliminated senescence.
Physiological Theories of Aging
- Free Radical Theory: Denham Harman, in “Aging: A Theory Based on Free Radical and Radiation Chemistry” (1956), proposed that free radicals generated during metabolism progressively damage DNA, proteins and lipids, producing cellular dysfunction and aging.
- Somatic Mutation Theory: Leo Szilard (1959) proposed that cumulative damage and mutations in somatic-cell DNA progressively impair cellular functioning. Modern studies confirm age-related accumulation of somatic mutations, although their precise causal contribution to normal aging remains debated.
- Cellular Senescence Theory: Leonard Hayflick and Paul Moorhead (1961) showed that normal human diploid cells possess a finite replicative capacity, later called the Hayflick limit. Progressive accumulation of non-dividing senescent cells may therefore contribute to tissue aging.
- Cross-linking Theory: Johan Bjorksten argued that increasing cross-linkages among long-lived macromolecules, particularly proteins such as collagen, reduce tissue elasticity and functional efficiency. Experimental work has demonstrated increased age-related protein cross-linking.
- Neuroendocrine and Immunological Theories: M. Dilman (1971) related aging to declining hypothalamic-endocrine regulation, while Roy Walford (1964) proposed that progressive deterioration of immune regulation contributes to senescence and age-associated disease.
Evolutionary Theories of Aging
- Evolutionary theories begin with the principle that the force of natural selection declines with age, especially after reproduction.
- Mutation Accumulation Theory: Peter Medawar, An Unsolved Problem of Biology (1952), argued that deleterious mutations expressed mainly in late life are only weakly removed by natural selection and can therefore accumulate.
- Antagonistic Pleiotropy: George C. Williams, in “Pleiotropy, Natural Selection, and the Evolution of Senescence” (1957), proposed that alleles beneficial to early survival or reproduction may be favoured even if the same alleles have harmful effects in later life.
- Disposable Soma Theory: Thomas Kirkwood (1977) argued that organisms possess limited energy and must trade off investment between reproduction and somatic maintenance. Natural selection favours sufficient repair to survive and reproduce, but not indefinite maintenance of the soma.
Declining selection with age → Imperfect maintenance/late-acting effects → Senescence
Critical Synthesis
Physiological theories identify proximate mechanisms of damage, whereas evolutionary theories explain why such imperfect maintenance and late-life deterioration can persist. Aging is therefore best understood as multifactorial, arising from interactions among genetic regulation, cellular damage, physiological decline and evolutionary trade-offs.
Conclusion
Aging cannot be explained by a single mechanism. The strongest anthropological understanding integrates physiological processes with life-history evolution, viewing senescence as the cumulative biological expression of imperfect repair under declining natural selection.
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UPSC Anthropology Optional 2021 — Paper I
28 questions1(a) Animism and Deep Ecology
10 Marks150 words
Syllabus: Paper I > 5. Religion > Forms of religion > Animism
Syllabus: Paper I > 12. Applications of Anthropology > Anthropology of sports; nutritional anthropology
1(d) “The bio-cultural approach is the hallmark of Biological Anthropology.” Explain.
10 Marks150 words
Syllabus: Paper I > 1.3 Main branches of Anthropology > Biological Anthropology
Syllabus: Paper I > 11.3 Biological and socio-ecological factors influencing fecundity and fertility
Syllabus: Paper I > 7. Culture, language and communication > Social context of language use
Syllabus: Paper I > 9.4 Chromosomes and chromosomal aberrations in man
2(b) Elucidate the concept of “thick description” of Clifford Geertz with a suitable example.
15 Marks
Syllabus: Paper I > 6. Anthropological Theories > Interpretive Anthropology > Geertz
5(d) Descent Groups
10 Marks150 words
Syllabus: Paper I > 2.5 Kinship > Descent groups
Syllabus: Paper I > 12. Applications of Anthropology > Applied human genetics > Paternity diagnosis
Syllabus: Paper I > 1.8(b) Cultural Evolution: broad outlines of prehistoric cultures > Neolithic
Syllabus: Paper I > 9.3 Mendelian population and Hardy-Weinberg law > Evolutionary mechanisms
1(c) Historical Particularism and Franz Boas
10 Marks150 words
Syllabus: Paper I > 6. Anthropological Theories > Historical Particularism (Boas)
5(a) Human adolescent growth spurt
10 Marks150 words
Syllabus: Paper I > 10. Human growth and development > Stages of growth > Adolescence
5(c) Is race a valid and biologically meaningful concept ?
10 Marks150 words
Syllabus: Paper I > 9.5 Race and racism > Biological basis of racial classification
Syllabus: Paper I > 2.5 Kinship > Alliance theory; structuralism
Syllabus: Paper I > 2.4 Family > Types and classification of the family
1(b) Marriage Regulations and Alliance Theory
10 Marks150 words
Syllabus: Paper I > 2.3 Marriage > Rules of marriage; alliance theory
5(e) Modes of Subsistence
10 Marks150 words
Syllabus: Paper I > 3. Economic Organization > Modes of subsistence
Syllabus: Paper I > 1.6 Phylogenetic status, characteristics and distribution > Homo erectus
Syllabus: Paper I > 10. Human growth and development > Ageing and senescence > Theories of ageing
3(a) How do political organisations of simple societies establish power, authority and legitimacy ?
20 Marks
Syllabus: Paper I > 4. Political Organization and Social Control > Power, authority and legitimacy
Syllabus: Paper I > 1.2 Relationships with other disciplines: Social Sciences
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
1(e) Thermoluminescence (TL) dating
10 Marks150 words
Syllabus: Paper I > 1.8(a) Chronology: relative and absolute dating methods
Syllabus: Paper I > 8.3 Research Methods: Tools of data collection
Syllabus: Paper I > 1.8(b) Cultural Evolution: broad outlines of prehistoric cultures > Mesolithic
Syllabus: Paper I > 2.2 The Nature of Society > Social stratification