History of Evolution
Monday, February 25, 2013
Scientific Knowledge is
• Empirical: based on observation of the world around you (usually quantitative)
o Based on observational and experimentation
• Testable: Often, but not always, through experimentation (If something can not be
tested, it is not science)
o Evolution to Biology is like:
• Gravitation: Physics
Plate Tectonics: Geology
o Some confusion cause by use of the term "theory" as applied to evolution.
Scientific theory: Well-established explanation of some part of the natural world
that can incorporate facts, laws, inferences, and tested hypothesis
• Key Points
A scientific theory includes multiple parts
No amount of validation changes a multipart theory of law
o Ex: Einstein's Theory of Relativity
o Like relativity, evolution is a theory that:
• Incorporates multiple facts (i.e., species change through time)
• Predictions of the unifying
• Bottom line: when you hear a scientist talking about a theory, it doesn't
imply any reservations whether it is correct of not.
What is evolution?
• General: change through time
Biological: change in gene (allele) frequencies within a population from one generation
to the next. *****
• Gene: small section of DNA that codes for a protein
• Alleles: variants of the same gene
• Important Notes: *****
o Population is the unit of evolutionary change (individuals don't evolve)
o Genetic material must change for evolution to occur (ex: good nutrition NOT
evolution) o Important point: We're all related
•Two levels of studying evolution:
• Short time frame (months, years)
• Genetic changes within a species
• Long time frame (often millions of years)
• Origin and extinction of species
A very brief History of Evolutionary thought
•Q: What did an educated European know about the natural world in 1492?
o European thought during the middle ages:
• Earth at center of universe (Ptolemy-140 A.D.)
• Earth very young
o James Ussher (1581-1656)
• Archbishop of Armagh
• Vice-Chancellor of Trinity College in Dublin
• Primate of All Ireland
• Earth created on Sunday October 23, 4004 BC
• John Lightfoot: vice Chancellor of Cambridge said at 9am London Time
o Plato "World of Ideals"
• For everything, there is an ideal or perfect counterpart
• If species based on a fixed "ideal type" how could they change through
• How to classify living things?
• Ladder of nature
• Organisms can be grouped on a linear scale from simple to
complex (of course, humans above beasts and plants…)
People weren't dumb: they DID recognize that animals were well-suited for their
• Explanation different than today's:
Teleology: the use of ultimate purpose or design as a means of
explaining natural phenomena (think divine purpose…)
o World young and at center of universe
o Fixity of species (no evolution-everything based on a platonic "ideal" type)
o Humans at top of scala naturae
Organisms successful at what they do, because that's how they were designed
•When did things start to change?
o Copernicus: responsible for saying that the earth rotated around the sun
• Don’t just trust the word of some Greek who's been dated for 1500 years,
go out and look for yourself
• Hypothesis testing using empirical data
• Refined refracting telescope
• Proved Copernicus was right and Ptolomy was wrong o So, the earth isn't at the center of the universe, but humans are still at the top of
the scala naturae, right?
o Carolus Linnaeus (1707-1778)
• Swedish Natrualist
• Founded modern taxonomy with System Naturae
• Bionomical classification
• Believed in teleological explanations of natural phenomena and fixity of
Used common attributes to group organisms
Grouped HUMANS with other primates in animal kingdom,
profound shift in thinking about place of humans in nature.
o Richard Owen (1804-1892)
• English Comparative anatomist
• Homology: Defined in 1843 as "the same organ in different animals under
every variety or form and function."
• Owen's explanation: there is a divinely-ordained archetype for living
organisms (common anatomical plans for diff. groups)
• But: pointed out basic similarities in anatomy in otherwise very different
o Georges Louis Leclerc, Comte de Buffon (1707-1788)
French aristocrat and naturalist
• Historie Naturelle (1749-1804)
44 volume encyclopedia
• One of the first prominent scientists to suggest that:
• The earth > 6000 y.o
• Species change over time
• Noted anatomical similarity between humans and apes and discussed
possibility of common ancestry (no mechanisms though)
o Jean Baptiste Lamarck (1744-1829)
• French naturalist born into poor aristocratic family
• Philosophie Zoologique
• First to propose a coherent mechanism to explain HOW evolution might
• Change through STRIVING
• ACQUIRED CHARACTERISTICS passed on to offspring (results
cumulative: EX giraffe's neck
• Mechanism was wrong
• BUT: said that stability of species is proportional to stability of the
• Therefore, if the environment changes, then species have to change to
• I.E., adaptation occurs over time in response to environmental change.
o Georges Cuvier
• French Paleontologist and Comparative Anatomist
• Anti-evolutionist and vocal critic of Lamarck
• Work with fossils from Paris Basin established extinction as a fact. • Explanation: Catastrophism
• Provided further evidence that the earth was OLD
o Charles Lyell (1779-1875)
• Scottish Geologist
• Didn't buy Cuvier's catastrophism.
• Same geological processes observable today also happened in past
• Given enough time, small changes can have a large effect.
• Inescapable conclusion: Earth very old.
o Thomas Malthus (1766-1834)
• English Clergyman, Economist and Natural Scientist
• Essay on the Principle of Population (1798)
• Compared European population growth with food production capacity:
Unchecked pop. Growth faster.
• Disease and other factors keep population in check
• Observation that (if left unchecked) the population will tend to increase