Module 2: Historical Perspectives on Evolution

Evolution

It is the gradual change in living organisms over generations.

Modern Evolutionary Biology

It is primarily associated with Charles Darwin’s theory of natural selection.

Anaximander

He suggested that life originated in water and gradually adapted to land.

Empedocles

He proposed that organisms were formed by chance combination of parts.

Aristotle

He advocated for a “Great Chain of Being” (Scala Naturae), suggesting species were fixed and arranged in a hierarchy.

Christian, Islamic, and Other Theological Views

They believed that species were immutable and created by a divine being.

Special Creation

It is the biblical concept that dominated natural history.

Jean-Baptiste Lamarck

He was a pioneering French naturalist and biologist best known for his early contributions to evolutionary biology.

Jean-Baptiste Lamarck

He proposed one of the first coherent theories of evolution, which emphasized the idea that organisms change over time in response to their environment.

Use and Disuse

Key Aspects of Lamarck's Evolutionary Theory

Lamarck suggested that organs and structures that are used frequently become stronger and more developed, while those that are not used deteriorate over time.

Inheritance of Acquired Characteristics

Key Aspects of Lamarck's Evolutionary Theory

Lamarck believed that traits acquired during an organisms lifetime could be passed on to offspring.

Complexification and Progress

Key Aspects of Lamarck's Evolutionary Theory

Lamarck proposed that life gradually progresses from simple to more complex forms through an inherent drive toward perfection.

Alfred Russel Wallace

He was a British naturalist, explorer, and biologist best known for independently conceiving the theory of evolution by natural selection alongside Charles Darwin.

Alfred Russel Wallace

Unlike Darwin, he emphasized the importance of environmental pressures over competitions in shaping species.

Alfred Russel Wallace

Later in his life, he argued that natural selection alone could not explain human consciousness and intellectm proposing a role for spiritual or supernatural elements in human evolution.

Alfred Russel Wallace

He was an early advocate for environmental conservation and sustainable resource management, emphasizing the impact of human activities on nature.

Alfred Russel Wallace

His key works, which further developed his evolutionary ideas, include:

• The Malay Archipelago (1869)

• Contributions to the Theory of Natural Selection (1870)

• Darwinism (1889)

Theory of Natural Selection

Wallace’s Key Contributions to Evolutionary Biology

• In 1858, Wallace sent a paper to Darwin outlining his ideas on natural selection, which he developed based on observations made during his travels in Southeast Asia (the Malay Archipelago). This prompted Darwin to publish his own ideas in On the Origin of Species (1859).

• Wallace's paper, On the Tendency of Varieties to Depart Indefinitely from the Original Type, was presented alongside Darwin’s work at the Linnean Society of London in 1858.

Wallace’s Line

Wallace’s Key Contributions to Evolutionary Biology

• Wallace conducted extensive fieldwork in the Amazon and the Malay archipelago, leading to the discovery of what is called [ ___ ], an imaginary boundary separating the distinct faunas of Asia and Australasia.

• Wallace’s work in biogeography helped establish the field as a scientific discipline, emphasizing the geographical distribution of species and their evolutionary origins.

Wallace’s Effect

Wallace’s Key Contributions to Evolutionary Biology

• Wallace proposed the idea that natural selection could lead to reproductive isolation and speciation by favoring individuals that avoid hybridization.

Wallace

Wallace or Darwin: He placed more emphasis on adaptation to the environment.

Wallace

Wallace or Darwin: He believed that human intelligence and morality could not be fully explained by natural selection alone.

Darwin

Wallace or Darwin: He took on a more materialistic view in explaining the development and evolution of human intelligence and morality.

Charles Darwin

He was an English naturalist, geologist, and biologist best known for his contributions to evolutionary biology.

Charles Darwin

His groundbreaking work, On the Origin of Species (1859), introduced the scientific theory that all species of life have descended over time from common ancestors through the process of natural selection.

Charles Darwin

His contributions continue to influence scientific disciplines, including genetics, ecology, and anthropolgy.

Theory of Evolution

It remains a conerstone of modern biology, explaining the diversity and adaptation of life on Earth.

Natural Selection

Key Concepts of Darwin’s Theory

• Organisms with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to their offspring.

• Over time, this leads to gradual changes in populations, leading to evolution.

Variation and Adaptation

Key Concepts of Darwin’s Theory

• Within a population, individuals show variation in traits, such as size, color, or behavior. Some of these variations provide an advantage in the struggle for survival.

• Traits that help organisms survive and reproduce become more common in the population.

Common Descent

Key Concepts of Darwin’s Theory

• All living organisms share a common ancestor, meaning that life evolved from a single origin and diversified over millions of years.

Survival of the Fittest

Key Concepts of Darwin’s Theory

• This phrase, popularized later by Herbert Spencer, describes how individuals with favorable traits are more likely to survive and reproduce in a given environment.

Gradualism

Key Concepts of Darwin’s Theory

• Evolution occurs slowly and gradually over long periods rather than in sudden jumps.

Voyage of the HMS Beagle

Darwin's Influences and Observations

• Darwin traveled to various places, most notably the Galápagos Islands, where he observed finches with different beak shapes adapted to their specific diets, leading to insights about adaptation and speciation.

Influence of Thomas Malthus

Darwin's Influences and Observations

• Darwin was inspired by [ ___ ]’s ideas on population growth and competition for resources, which helped shape his theory of natural selection.

Lamarck’s Earlier Ideas

Darwin's Influences and Observations

• [ ___ ] proposed an earlier, incorrect theory of evolution based on acquired traits, but it influenced Darwin's thinking.

Scientific Revolution

Impact of Darwin’s Work

• Darwin's ideas challenged the prevailing belief in divine creation and fixed species, laying the foundation for modern evolutionary biology.

Genetics and Modern Evolutionary Synthesis

Impact of Darwin’s Work

• Later discoveries in genetics, particularly by Gregor Mendel and the field of DNA research, provided mechanisms to support and expand Darwin's theory.

Creationism

Darwin’s ideas were initially met with skepticism and resistance, especially from religious communities that believed in [ ___ ]. However, his theory gradually gained widespread acceptance within the scientific community.

Modern Synthesis

It is a central framework in evolutionary biology that emerged in the early to mid-20th century.

Modern Synthesis

It integrates Darwinian natural selection with Mendelian genetics, providing a unified explanation of how evolution occurs through genetic changes in populations over time.

Population Genetics

Key Concepts of the Modern Synthesis

• Evolution occurs at the level of populations, where genetic variation is acted upon by natural selection.

• Key figures such as Ronald Fisher, J.B.S. Haldane, and Sewall Wright developed mathematical models to describe how allele frequencies change over generations.

Ronald Fisher, J.B.S. Haldane, and Sewall Wright

They developed mathematical models to describe how allele frequencies change over generations.

Genetic Variations

Key Concepts of the Modern Synthesis

• Mutations, genetic recombination, and gene flow introduce variation in populations.

• This variation is the raw material for evolution, with beneficial traits being selected for over time.

Natural Selection as a Mechanism

Key Concepts of the Modern Synthesis

• Darwin’s idea of [ ___ ] is reinforced with the understanding that beneficial genetic variations increase in frequency, leading to adaptation.

Speciation and Macroevolution

Key Concepts of the Modern Synthesis

• Gradual changes in populations can lead to the formation of new species through mechanisms such as genetic drift, geographic isolation, and reproductive barriers.

Gradual Evolution

Key Concepts of the Modern Synthesis

• The Modern Synthesis posits that evolution occurs through the slow accumulation of small genetic changes rather than sudden transformations.

Microevolution and Macroevolution Linkage

Key Concepts of the Modern Synthesis

• Microevolutionary processes (changes in allele frequencies) can scale up to macroevolutionary patterns (the emergence of new species and higher taxonomic groups).

Theodosius Dobzhansky

Contributors to the Modern Synthesis: He linked genetics and natural selection in his work titled, “Genetics and the Origin of Species” (1937).

Ernst Mayr

Contributors to the Modern Synthesis: He emphasized species concepts and geographic speciation.

George Gaylord Simpson

Contributors to the Modern Synthesis: He integrated paleontology with evolutionary theory.

Julian Huxley

Contributors to the Modern Synthesis: He popularized the synthesis and provided a comprehensive framework in the work titled, "Evolution: The Modern Synthesis” (1942).

Evolutionary Developmental Biology

Limitations and Extensions of the Modern Synthesis

• It examines how changes in gene regulation during development influence evolutionary change.

Neutral Theory of Molecular Evolution

Limitations and Extensions of the Modern Synthesis

• It was a theory proposed by Motoo Kimura.

• It emphasized the role of genetic drift in evolution.

Epigenetics

Limitations and Extensions of the Modern Synthesis

• It explores how non-genetic factors influence gene expression and can affect evolutionary processes.

Horizontal Gene Transfer

Limitations and Extensions of the Modern Synthesis

• It is specially important in microbial evolution, showing gene movement between species.