Theories of Evolution: From Lamarck to Neo-Darwinism
The Theories of Evolution topic is crucial for UPSC GS Paper 3 (Science & Technology) and Anthropology Optional as it explains the biological and genetic foundation of life’s diversity. Understanding Lamarck’s and Darwin’s theories alongside Neo-Darwinism helps aspirants grasp human evolution, genetic adaptation, and species formation—core areas in modern biology and anthropology. It also supports cross-disciplinary insights into ethics, environmental adaptation, and genetic engineering, frequently linked with UPSC Mains and Prelims questions.
Introduction
The theory of evolution forms the cornerstone of modern biology, explaining how organisms change over generations through natural processes. It helps us understand the diversity of life, human origins, and the adaptation of species to their environments. Evolutionary theory bridges genetics, ecology, and anthropology, revealing that all living organisms share a common ancestry. From Lamarck’s early ideas to Darwin’s revolutionary insights and the genetic synthesis of the 20th century, the theory’s development reflects humanity’s evolving understanding of life’s complexity.
Early Ideas: Lamarck’s Theory of Inheritance of Acquired Characters
Jean-Baptiste Lamarck (1809) was the first to propose a cohesive scientific theory of evolution. His theory, known as the Inheritance of Acquired Characters, suggested that traits acquired during an organism’s lifetime due to use or disuse of organs could be passed to offspring.
Key Principles
- Use and Disuse: Organs used frequently become stronger, while unused organs weaken and eventually disappear.
- Inheritance of Acquired Traits: Acquired traits (like strength or flexibility) are inherited by the next generation.
- Adaptation to Environment: Changes occur as organisms strive to meet environmental challenges.
Examples and Significance
- Giraffe’s neck: Giraffes evolved long necks because their ancestors stretched to reach high leaves; the trait was passed to descendants.
- Though experimentally disproved by August Weismann’s germplasm theory, Lamarck’s ideas influenced later evolutionary thought by emphasizing environmental impact and adaptation.
Darwin’s Theory of Natural Selection
Charles Darwin (1859) revolutionized biology with his book On the Origin of Species. His theory explained evolution as a gradual process driven by natural selection—the differential survival and reproduction of individuals with advantageous traits.
Core Principles
- Variation: Individuals in a species vary genetically and physically.
- Overproduction: More offspring are produced than can survive.
- Struggle for Existence: Competition for limited resources ensures survival of the fittest.
- Natural Selection: Fitter individuals pass on favorable traits to their offspring.
- Speciation: Over generations, accumulation of variations creates new species.
Examples
- Peppered moths in England: Dark moths survived industrial pollution better due to camouflage.
- Finches on the Galápagos Islands: Their beak sizes adapted to available food.
Darwin’s work, supported by Alfred Russel Wallace, reinforced the view that evolution is a continuous, natural process, without divine intervention.
Modern Synthetic Theory (Neo-Darwinism)
By the early 20th century, Darwin’s ideas merged with Mendel’s genetics, forming the Modern Synthesis, also known as Neo-Darwinism.
Key Components
- Mutation: Random genetic changes introduce variations.
- Recombination: Gene exchange during sexual reproduction increases genetic diversity.
- Natural Selection: Favors beneficial mutations.
- Genetic Drift: Random changes in allele frequencies affect small populations.
- Isolation: Geographic or reproductive barriers lead to speciation.
Prominent contributors include Theodosius Dobzhansky, Julian Huxley, and Ernst Mayr, who unified ecology, genetics, and evolution into one comprehensive framework.
Criticism and Alternative Views
1. Mutation Theory – Hugo de Vries (1901)
Proposed that evolution occurs through sudden genetic mutations, not gradual change. Later research integrated this concept into Neo-Darwinism.
2. Punctuated Equilibrium – Eldredge and Gould (1972)
Argued that evolution is not always gradual but happens in rapid bursts followed by long periods of stability.
3. Endosymbiotic Theory – Lynn Margulis (1960s)
Suggested that complex eukaryotic cells evolved from symbiotic relationships among simpler organisms—an idea challenging Darwinian gradualism.
Relevance in the Indian Context
Contributions of Indian Scientists
- Birbal Sahni: Pioneer in paleobotany, studied evolution of ancient plant species.
- Satish Dhawan: Supported studies in evolutionary dynamics in relation to space biology.
- Sewall Wright and J.B.S. Haldane (an Indian citizen by adoption) made foundational contributions to population genetics.
Anthropological Perspective
- In UPSC Anthropology Optional, evolution is central to understanding human evolution, fossil evidence, and primate adaptation.
- Fields like evolutionary anthropology explore how natural selection shaped human behavior and culture, integrating biology with social sciences in India’s academic context.
Conclusion
The evolution of evolutionary thought—from Lamarck to modern genetics—demonstrates science’s power to refine itself through observation, experiment, and synthesis. Evolution reshaped humanity’s self-image, bridging philosophy, biology, and anthropology. Today, it continues to underpin biology and genetics, guiding fields from medicine to evolutionary psychology, while reminding us of our shared ancestry and constant transformation.
Key Concepts for Prelims
| Theory / Scientist | Core Idea | Example |
|---|---|---|
| Lamarckism | Inheritance of acquired traits | The giraffe’s long neck |
| Darwinism | Natural selection favors heritable variations | Finches’ beak variations |
| Mutation Theory | Sudden genetic changes create new species | Evening primrose mutations |
| Neo-Darwinism | Integration of genetics, mutation, and selection | Population evolution models |
| Punctuated Equilibrium | Rapid evolution with long stasis | Fossil record patterns |
Analytical Insights for Mains (GS Paper 3 / Anthropology)
- GS Paper 3: Theories of evolution form the basis of studying biodiversity, genetic engineering, and climate adaptation.
- Anthropology Optional: Analysis of human evolution through fossil evidence, environmental adaptation, and genetic continuity connects directly to UPSC Unit 1.4 syllabus.
- Ethical Angle: Evolutionary theory also influences socio-philosophical debates on human origin and coexistence.
Frequently Asked Questions (FAQs)
Q1: What is the theory of evolution?
The theory of evolution explains how species change over generations through variations, natural selection, and adaptation, leading to the origin of new species.
Q2: Who proposed the theory of inheritance of acquired characters?
Jean-Baptiste Lamarck (1809) proposed it, suggesting that traits acquired during an organism’s lifetime can be passed to its offspring.
Q3: What are the key principles of Darwin’s theory of natural selection?
Darwin emphasized variation, overproduction, struggle for existence, and survival of the fittest, explaining evolution as a product of natural selection.
Q4: What is Neo-Darwinism or Modern Synthetic Theory?
It is the modern extension of Darwinism that integrates genetics, mutation, natural selection, and population biology, forming the foundation of modern evolutionary biology.
Q5: Why is the study of evolution relevant today?
It underpins genetics, biodiversity conservation, medicine, and biotechnology—offering insights into adaptation, heredity, and human origins.
