Evolutionary Theory: From Pre-Darwinian Ideas to Modern Genetics

Divine creation stories

Stories that describe a Supreme Being creating life and placing it on Earth, where creations are immutable.

Anaximander

A 6th century BCE Greek thinker who proposed that all organisms descend from common ancestors, predating Darwin's theory of transmutation by approximately 2,400 years.

Carolus Linnaeus

A scientist known for developing binomial nomenclature and a hierarchical classification system to recognize similarities due to shared ancestry.

Binomial nomenclature

A system for naming species using two terms, the first identifying the genus and the second the species, e.g., Homo sapiens.

James Hutton

The founder of modern geology who promoted uniformitarianism and introduced the concept of the great geological cycle.

Uniformitarianism

The principle that the present is the key to understanding the past, suggesting that geological processes occur at the same rate over time.

Great geological cycle

The cycle of erosion and sedimentation that leads to the continuous renewal of the Earth's crust.

Adam Smith

A philosopher and economist who proposed the concept of the invisible hand, suggesting that self-interest in free markets leads to beneficial societal outcomes.

Invisible hand

A metaphor for the unseen forces that move the free market economy, where individual self-interest leads to economic benefits for society.

Natural selection

The process by which organisms with advantageous traits survive and reproduce, shaping the population without purposeful direction.

Jean-Baptiste Lamarck

A scientist known for his theory of evolution through use-and-disuse and inheritance of acquired traits, although with incorrect mechanisms.

Use-and-disuse theory

Lamarck's theory suggesting that traits acquired or lost during an organism's lifetime can be passed on to its offspring.

Hierarchy of classification

A system developed by Linnaeus that organizes living organisms into a nested structure: Kingdom → Phylum → Class → Order → Family → Genus → Species.

Gradual biological change

The concept that biological evolution occurs slowly over a long period, requiring a vast timescale.

Common descent

The idea that all living organisms share a common ancestor.

Erosion

The process by which rock and soil are worn away, contributing to the geological cycle.

Sedimentation

The process of depositing material that has been eroded, contributing to the geological cycle.

Philosopher/economist

An individual who studies the nature of knowledge, reality, and existence, often in relation to economic principles.

Wealth of Nations

A book written by Adam Smith that discusses economic principles and the benefits of free markets.

Optimal outcomes

Results that are most favorable or advantageous, often achieved through competition in free markets.

Vast timescale

The extensive period required for gradual biological changes to accumulate, as suggested by Hutton's geological observations.

Divine plan

The belief that the organization of biodiversity reflects a purposeful design by a Supreme Being.

Competition

The struggle between organisms for limited resources, which can lead to natural selection.

Lamarck's Theory of Acquired Traits

Key idea: Traits acquired during an individual's life can be passed to offspring.

Giraffe Example

Giraffe A feeds on short shrubs → short neck. Giraffe B stretches to eat tall trees → longer neck as an adult.

Flaw in Lamarck's Theory

The longer neck is not inherited; newborns are born with the species-average neck length.

Analogy for Lamarck's Theory

A bodybuilder who develops massive muscles will not give birth to a baby with the same muscularity.

Modern Nuance on Epigenetics

Emerging research shows that parental behaviors can modify gene expression and sometimes be transmitted to later generations.

Thomas Malthus

Core observation: Human populations tend to grow geometrically while food supplies increase linearly.

Malthus's Consequences

1. Competition for limited resources. 2. Periodic crises (famines, wars, epidemics) that reduce the population back toward the carrying capacity.

Population Growth Type

Geometric growth represented by an exponential curve.

Food Supply Growth Type

Linear growth represented by a straight line.

Impact on Darwin from Malthus

Malthus's insight that resources are limited inspired the idea that struggle for existence could drive natural selection.

Georges Cuvier

Founder of paleontology and comparative anatomy.

Cuvier's Contributions

Demonstrated that African and Indian elephants are distinct species and showed that mammoths are a separate, extinct species.

Catastrophism

Philosophy that Earth's history is shaped by sudden, massive disasters that cause extinctions, followed by the appearance of new life forms.

Darwin's Synthesis

Darwin synthesized ideas from Linnaeus, Hutton, Smith, and Lamarck into the theory of natural selection.

Linnaeus's Hierarchy

Highlighted patterns of similarity among organisms.

Hutton's Deep Time

Supplied the necessary temporal canvas for understanding evolution.

Smith's Invisible Hand

Offered a model for competition-driven change.

Differential Survival

Natural selection replaced Lamarck's inheritance of acquired traits with differential survival of heritable variation.

Geological processes

Erosion and sedimentation that operate gradually over immense periods.

Relevance to evolution

Provided the temporal framework necessary for slow biological change to accumulate.

Charles Lyell

Proponent of uniformitarianism, which states that the present is the key to the past.

Charles Darwin

Formulated the theory of natural selection.

Steps of Natural Selection

1. Variation - Individuals in a population exhibit heritable differences. 2. Differential survival - Those with advantageous traits are more likely to survive. 3. Reproduction - Survivors reproduce, passing favorable traits to offspring. 4. Accumulation - Over many generations, advantageous traits become more common.

Chronology of Key Figures

Timeline of significant scientists and their contributions to evolutionary theory.

Charles Lyell's contribution

Developed uniformitarianism and published Principles of Geology.

Charles Darwin's contribution

Formulated the theory of natural selection in 1859.

The Voyage of the HMS Beagle

Darwin served as gentleman's companion to Captain Robert FitzRoy, collecting specimens and making observations.

Glyptodon fossils

Found giant armadillo fossils in strata alongside modern seashells, providing evidence of recent extinction without catastrophe.

Galápagos observations

Darwin noted that mockingbirds differed by island, leading to the identification of 12 distinct finch species.

Post-Voyage Analysis

A team of naturalists catalogued Darwin's collections upon his return to England.

Influence on Darwin

Lyell's emphasis on long, steady change convinced Darwin that natural selection could act over millions of years.

Intellectual lineage

Connections between Malthus, Hutton, Lyell, and Cuvier's ideas that shaped Darwin's theories.

Darwin's early education

Initially pursued medicine but left medical school, later trained as an Anglican priest at Cambridge.

Darwin's activities at Cambridge

Spent time riding horses and hunting while connecting with a natural historian.

Darwin's seasickness

During the voyage on the HMS Beagle, Darwin suffered seasickness and spent about two-thirds of the time on land.

Mockingbirds identification

Local inhabitants could identify a bird's island of origin by sight.

Transmutation of species

Early term for the evolution of one species into another.

Struggle for existence

Competition for limited resources driving natural selection.

Wallace's Line

Biogeographic demarcation separating distinct faunal regions in the Malay Archipelago.

Malthusian pressure

Population growth outpacing resources, prompting competition.

Alfred Russel Wallace

Naturalist who independently developed a theory of natural selection parallel to Darwin.

HMS Beagle

The ship on which Darwin made his key observations during his voyage (1831-1836).

Malthus's Essay on Population

The work that influenced Darwin's ideas on natural selection in 1838.

Gregor Mendel

Scientist who discovered the laws of inheritance, providing a genetic mechanism for variation.

Rosalind Franklin

Scientist who produced critical X-ray diffraction images of DNA.

Watson & Crick

Scientists who described the double-helix structure of DNA.

On the Origin of Species

Darwin's 1859 publication that revolutionized biology.

Joint presentation to the Linnean Society

The 1858 event where Darwin and Wallace presented their findings on natural selection.

Faunal break

The sharp distinction in species between Bali and Lombok identified by Wallace.

Geographic gap

The ~20 mi strait between Bali and Lombok that marks Wallace's Line.

Inheritance

The process through which genetic information is passed from parents to offspring.

1858 fever

The urgency that led Wallace to rapidly send his manuscript on natural selection to Darwin.

Core principle of natural selection

As many more individuals of each species are born, they can possibly survive, leading to natural selection.

1859

The year Darwin published 'On the Origin of Species'.

1866

The year Gregor Mendel's work on inheritance gained recognition.

1953

The year Watson & Crick published the structure of DNA based on Franklin's data.