Darwin

Darwin’s achievements

• Made evolution widely accepted.

• Replaced essentialism with the idea of changing, variable species.

• Proposed natural selection.

• Explained organism “design” without invoking purpose or divine planning.

Who influenced Darwin at Edinburgh?

learned from Robert Grant (a zoologist and Lamarckian) and Robert Jameson, who taught a /naturalist course.

Darwin on the Beagle — what was his role?

• served as the ship’s naturalist,

• collected specimens and observing animals, plants, and geology.

  • gave him key evidence for later forming his evolutionary ideas.

What was evolution called before

Species transmutation

Why did Darwin keep his 1844 essay secret?

• Fear of backlash (religious + scientific).

• His ideas were radical—species changing wasn’t accepted.

• Wanted much more evidence before going public.

What was Darwin working on in 1856, and why?

He began writing a 1000-page book called Natural Selection, encouraged by Lyell and Hooker, who warned him he might be scooped by others.

What did Darwin do after abandoning his 1000-page Natural Selection, and what did The Origin of Species explain?

He wrote The Origin of Species, which explained..

• natural and artificial selection,

• common descent,

• evidence from morphology

• embryology

• vestigial organs

• biogeography

• fossils.

What were Darwin’s proposed causes of evolutionary change?

Natural selection and use and disuse

What were Darwin’s views on variation and heredity?

• Variation:

  • Conspicuous (sport) variation

  • Continuous (individual) variation

• Heredity: Traits are passed via gemmules, tiny particles carrying information from all parts of the body to offspring.

What was Fleeming Jenkin’s critique of Darwinian evolution?

• Small genetic variants (individual variation) cannot push species beyond fixed limits.

• Large variants (sports) are quickly blended out by sexual reproduction, making them ineffective for long-term change.

What was A.W. Bennett’s critique of Darwinian evolution?

argued that natural selection couldn’t produce complex adaptations requiring many steps, because each step would have to be small yet beneficial.

What was Lord Kelvin’s critique of Darwinian evolution?

Claimed the Earth was too young for natural selection to produce the diversity of life

• because the Sun’s energy reserves were insufficient for a long enough habitable period.

Why was Darwinism considered “dead” by 1900, and what was missing?

• Darwinism (natural selection) lacked evidence from heredity, which wasn’t studied scientifically until later.

• Genetics and evolutionary biology were united in the Modern Synthesis (1900s–1940s).