The True Story of theTheory of Evolution

Or Fitzroy, Fickle Fuegians, and Funny, Feathered Finches

1973: “Nothing in biology makes sense, except in the light of evolution.”

-Theodosius Dobzhansky (1900-1975)

Evolution, Pre-Darwin

Beginnings in Ancient Greece Species are changeable… Variation occurs! Selective breeding utilized already “Artificial Selection”

Widely accepted in early-1800s: Lamarck’s Theory of Acquired Characteristics

Jean-Baptiste de Lamarck 1744-1829

1. Individuals lose characteristics they do not require (or use) and develop characteristics that are useful

2. Individuals inherit the traits of their ancestors.

Thomas Malthus Malthus: An Essay on The

Principles of Populations (1798)

Populations grow exponentially while food supply grows linearly.

Eventually population will outgrow food supply; life is a constant struggle

What keeps a population in check? War, pestilence, famine, competition, etc.

Charles Lyell

Principles of Geology (1830)

“The present is the key to the past.”

Geologic change is the steady accumulation of tiny changes over a lengthy period of time.

Charles Robert Darwin Born in 1809, same day

as Lincoln

Wealthy, upper-class

Father, Robert, was a physician and anti-evolutionist

Grandfather, Erasmus, was pro-evolutionist and gifted debater

Darwin’s Career

Robert: “You will be a disgrace to yourself and all of your family”

Eventually earned a degree in divinity from Cambridge

The HMS Beagle

First voyage: May 22, 1826

Captain Pringle Stokes Mission: survey coast

of southern South America

First Voyage of the Beagle

Stokes – suicide Robert Fitzroy

becomes captain: seeking a literal, biblical interpretation of creation

Boat stolen Fuegians captured as

hostages, then returned to England

The Beagle’s Second Voyage

Darwin – captain’s companion

Fitzroy and Darwin – devoted observers of the natural world

IMPORTANT – Darwin did not SET OUT to discover natural selection

Darwin’s Finches

Galapagos islands (Pacific Ocean)

Finches uniquely related to the individual islands

Ornithologist John Gould helped Darwin make his…

HYPOTHESIS: Modification of original group of finches that colonized islands

Megatherium

Darwin’s Later Life

Returned to England in 1836 and never left again

Suffered frequent illnesses, probably tropical in nature

Married his cousin, Emma Wedgewood

Son Charles fell critically ill in June, 1858

Evolution, Post-Darwin Wallace sends his

manuscript – 1858 Darwin faces pressing

dilemma – to present or not to

Darwin and Wallace present together on July 1, 1858

Around 1900, Mendel’s papers were “re-discovered”, as many scientists attempted to merge the two theories.Alfred Russell Wallace

On the Origin of Species (1859)

Caused controversy in religious and scientific communities

Darwin did not use the term “evolution” and did not suggest humans descended from apes

Questions remained for Darwin… “The eye to this day gives me a cold shudder...”

Theory did not gain wide acceptance until 1930s-40s

Premises of Natural Selection1. Populations overproduce.

2. Resources are limited, so competition ensues.

3. Genetic variations directly impact the ability of organisms to survive.

Premises of Natural Selection

4. Organisms with beneficial differences will have a better chance of survival.

5. Surviving individuals pass their traits onto future generations.

6. This results in a slow change in populations over time.

Natural Selection

process by which individual organisms with favorable traits are more likely to survive and reproduce

IMPORTANT – Individuals do not evolve. Populations evolve.

KEY DEFINITIONS Population: all members of a

species in one area

Species: Group of organisms that can produce fertile offspring

Variation: slight differences among organisms, often caused through genetic mutations

KEY DEFINITIONS Adaptation: Trait that affords

organism a better chance of survival

Evolution: Gradual change in a species over time***

Natural Selection: One mechanism through which evolution occurs

Adaptive Radiation: multiple species descend from one original species because of selection

Darwin’s Mechanisms for Evolution

1. Natural Selection

2. Whatever would cause “nature” to select for such a ridiculous tail on this peacock?