intro to Evolution

Philosophy & History of Pre-Evolution & Evolution

Lamarck's Giraffe Example

• Suggests that the stretching of a giraffe's neck, driven by an inner need to reach higher leaves, leads to progressively longer necks over generations.

Learning Objectives

At the conclusion of this topic, students will be able to:

• Explain the evolution of ideas regarding the history of life from creationist to naturalist perspectives.

• Outline key pre-evolutionary thinkers and their contributions to evolutionary thought.

• Recognize the significance of the history of thought in the evolution of ideas.

• Understand that the concept of evolution did not emerge out of nowhere but was influenced by earlier thinkers.

• Appreciate how classical Greek ideas, rooted in intelligent design, shaped views on life for centuries.

• Analyze how Charles Darwin integrated his ideas with those of his predecessors.

Teleology and Creationism

Definitions

• Teleology: The philosophical idea that purpose and design govern nature, encompassing goal-directed evolution.

• Creationism: The belief that life, Earth, and the universe are the creations of a supernatural being.

• Intelligent Design: The argument that certain features of the universe and living things are better explained by an intelligent cause rather than an undirected process like natural selection.

Classic Greek Contributions

Aristotle (384-322 B.C.)

• Known as the Father of Western Logic.

• Proposed the Scala Naturae, a hierarchy of life forms with each species occupying its own position on a ladder of complexity.

• Suggested species are permanent, perfect, and do not evolve; this belief dominated for 2,000 years.

The Old Testament Perspectives

• Asserts that all organisms result from a creator's direct actions, each with a specific role (teleology).

• Each organism is believed to have been handcrafted to fit perfectly into its environment.

• Popular belief was that the Earth is approximately 6,000 years old, and the universe is around 13,000 years old, though this varied.

Non-Western Contributions to Evolutionary Thought

• Contributions from other cultures, including Hindu, Buddhist, Hebrew, and notably Islamic traditions, were still heavily religious.

• During the 'Dark Ages,' the ideas of Aristotle and other Greeks were preserved and re-evaluated by Islamic scholars.

• Despite this, views on evolution remained largely creationist.

Evolutionary Thinkers of the 18th - 19th Century

Carl von Linne (Linnaeus)

• Known as the Father of Modern Taxonomy, Linnaeus contributed to the classification of species.

• Introduced the binomial nomenclature, seeking to catalog life for the glory of God without implying evolutionary relationships.

James Hutton

• Regarded as the Father of Geology, he introduced Gradualism, proposing that extensive changes in the Earth's structure result from gradual processes over time.

• Separated geological epochs and considered the Earth as active and changing, implying a much older age than previously thought.

Jean-Baptiste Lamarck

• Proposed Lamarckism, the idea that acquired characteristics could be inherited, marking a step toward evolutionary theory.

• Suggested a universe in which Earth is old with no extinction events; complexity arose through spontaneous generation.

Georges Cuvier

• The Father of Comparative Anatomy and Palaeontology, he established principles of extinction and catastrophism.

• Challenged the notion of gradual evolution, asserting that fossil forms did not generally transition into new species.

Étienne Geoffroy St. Hilaire

• Expanded on Lamarck’s theories, highlighting the underlying unity of organismal design via homologous structures.

Charles Lyell

• A friend of Darwin, he popularized Uniformitarianism, asserting that natural laws experienced today also applied to the past, thus influencing Darwin's geological perspectives.

Erasmus Darwin

• Charles Darwin’s grandfather, who speculated on the evolution of warm-blooded animals from a single living filament in his work "Zoonomia."

The Context of Darwin’s Era

• During Darwin's time, many thinkers debated the rate and mechanisms of evolutionary change.

• Science was heavily interlinked with religion and species were often viewed as fixed within a hierarchical context.

Darwin's Early Education and Interests

• Darwin showed little academic interest and disliked medical studies, preferring natural history.

• He engaged with influential figures such as Robert Grant, who introduced him to Lamarckian ideas.

The Voyage of the HMS Beagle

• Darwin embarked on a significant journey on December 27, 1831, which allowed him to observe diverse life forms and geological features across various islands.

• Notable observations included variations in finches on the Galapagos Islands, leading him to contemplate natural selection and adaptation.

The Development of Darwin’s Ideas

Influences and Discoveries

• Interactions with naturalists like John Gould, who identified unique finch species, broadened Darwin’s perspective on species diversity.

• Darwin’s readings of Thomas Malthus on population pressures inspired thoughts on survival struggles in nature.

Publication and Impact of Darwin's Work

On the Origin of Species

• Published in 1859, it integrated significant concepts such as artificial selection, natural selection, and gradualism.

• The book generated varied reactions and discussions within scientific and religious communities, modifying the landscape of biological sciences.

Reception of Darwin’s Ideas

• Initially met with skepticism, with Darwin's supporters being few. However, over time, his theories laid the groundwork for a shift from static to dynamic views of nature.

Key Figures Supporting and Critiquing Darwin

• Thomas Huxley emerged as an ardent supporter, while critics such as Sir Richard Owen acknowledged certain evolutionary elements but rejected human descent from apes.

Summary of Key Changes in Darwin's Time

• Shifts in thought included a view of a non-static universe, a move away from teleological explanations, recognition of species' mutability, and the dawn of biological sciences governed by natural laws.