The History of Evolutionary Thought

 
NOTE: The linked names on this page are just for your further interest. 
          You will not be held responsible for information on these pages.
 
I. Ancient Beliefs
 A. Plato (428-348 BC)
 1. idealism
  a. the "idea" is an eternal, unchanging essence
  b. variation has no meaning, only essence matters
 
 B. Aristotle (384-322 BC)
 1. Scala Naturae or scale of nature
 2. from inanimate to plants to animals to man
  a. permanent, unchanging
  b. everything fixed in place according to God's plan
 
 C. The views of these two early Greeks prevailed for almost 2000 years.
 
II. Beginning of Modern Scientific Methods and Thoughts (Image)
 A. Traditional beliefs
 1. all organisms resulted from direct actions of a creator
 2. role of natural science was to catalogue the organisms 
     and appreciate God's great wisdom
 3. Earth was about 6,000 years old
 
 B. Carolus Linnaeus (1707-1778)
 1. father of taxonomy
 2. clustered groups into a hierarchy of increasingly general categories (Image)
 3. done for the greater glory of god - "God's Registrar"
 
 C. Georges-Louis Leclerc, Comte de Buffon (1701-1788)
 1. French naturalist
 2. large inheritance freed him from having to earn a living
 3. suggested in 1779 that the earth might be very old (very heretical at the time)
 4. also discussed the relationship between apes and humans
 5. condemned by the Catholic Church in France and his books were burned
 
 D. Georges Cuvier (1769-1832) Image Wikipedia
 1. founder of paleontology (studied fossils - Image) - anatomist
 2. observed that different strata of sedimentary layers contained different fossils. Image.
 3. catastrophism--explained changes in animal world in terms of catastrophes that had 
 destroyed whole populations of living things in prehistoric times (floods etc.)
 
 E. James Hutton (1726-1797) and Charles Lyell (1797-1875)
 1. both were influential geologists
 2. James Hutton
  a. same processes are responsible for both past and present events 
 -uniformitarianism - Fig 22.4 and movie
  b. one of first to imply great age of the earth
 3. Charles Lyell Image
  a. great champion of Hutton's work
  b. historical and physical continuity of nature
  c. Principles of Geology (1830)--greatly influenced Darwin even though he 
 himself did not admit biological evolution
  d. small forces acting over long periods of time can result in major changes
 e.g. destruction of mountains
 
 G. Jean-Baptiste Lamarck (1744-1829) Image
 1. the first uncompromising advocate of evolution, attempted to provide a  
 mechanism to explain evolution
 2. argued that lowly forms of life arise continually from inanimate matter by
  spontaneous generation, and progress inevitably toward greater complexity and perfection 
 by "powers conferred by the supreme author of all things"--that is by an inherent tendency 
 toward complexity
 3. inheritance of acquired characteristics
 4. emphasized great age of earth
 
III. Charles Darwin (1809-1882) Darwin in 1874
 
 A. Early life
 1. born in 1809 in Shrewsbury, England--the son of a physician
 2. studied medicine in Edinburgh
 3. studied theology in Cambridge--was very religious
 4. at both places he pursued an interest in natural science
 
 B. Voyage of the H. M. S. Beagle (1831-1836)
 1. served as unpaid naturalist
 2. made stops along coasts and islands of the southern hemisphere
 3. noted how plant and animal forms differed with geographical location
 4. Observed fossils vs. extant species
 5. Observations in Galapogos Islands and South America. Drawings
 6. Read Lyell's Principles of Geology on the voyage - true age of earth 
 much greater than 6000 years
 
 C. Return to England after voyage
 1. did not accept notion of evolution until it was pointed out that his 
 specimens of finches (fig. 2.5) from Galapogos were so distinct as to represent different species
 2. this revelation led him to doubt the fixity of species
 3. first published several volumes on geology and the voyage of the Beagle
 
IV. Darwin's Evidence
 A. Hutton and Lyell's evidence supporting geological events.
 
 B. Observations
 1. extinct species related to living (extant) organisms
   a. observations of the fossil record
  b. e. g. armadillos and glyptodont (fig. 2.4) 
 --found fossil species similar to extant species
  c. if both were created at the same time, and if they were so much alike,
  why was only one of them alive in 1850?
 2. characteristics of species varied from place to place
  a. appearance of tortoises dependent on location
  b. slight changes in appearance after island isolation
 3. great variety of organisms on young volcanic islands, e.g., finches
 4. resembled forms on mainland, not distant places
 *organisms in forests of S. America more similar to organisms 
 of  grasslands of S. America than to organisms in forests of Europe
 *this would not be so if were created all at once to be perfectly 
 adapted for that environment.
 
 C. Darwin and Malthus
 1. Malthus wrote Essay on the Principle of Population (1798)
  a. argued that unchecked growth of the human population must 
 lead to famine
      *populations increase geometrically. (Fig. 2.6)
      *food supplies increase arithmetically
  b. nature acts to check population growth via death
      *in humans this is famine, war, and disease
 2. Led Darwin to his idea of natural selection
 
 D. Natural Selection
 1. the differential reproduction of individuals that differ in 
     one or more hereditary characterisitics
  a. difference in survival and/or reproduction not due to chance
  b. has the potential consequence of altering the proportions of 
 different characters
 3. changes the nature of the population as a whole
 
V. Publication of Darwin's Theory
 A. First draft completed in 1844, but was not published
 
 B. Began work on Natural Selection in 1856, was to be a 20 volume set
 
 C. Alfred Russel Wallace 
 1. was a British army surgeon stationed in Malaysia who studied insects
 2. wrote Darwin a letter in which he stated his theory of evolution by 
 natural selection and told Darwin he thought he knew how evolution worked
 3. this resulted in Darwin publishing The Origin of Species (1859) 
 (Fig. 2.7) rather than the 20 volume set he was contemplating.
 
 
 D. First edition said descent with modification (Fig 2.8)--did not use term evolution
 
VI. Evolutionary Theory After Darwin
 
 A. The mechanisms of heredity
 1. genes unknown in Darwin's time
 2. Mendel's theory rediscovered 1900
 3. at first scientists used Mendel's work to discredit Darwinian evolution
 4. later (1920's) determined that laws of inheritance explain genetic variation
 
 B. Modern synthesis--forged the contributions of genetics, systematics and paleontology.
 1. Populations contain genetic variation that arises by random 
     mutation and recombination
 2. Populations evolve by changes in gene frequency brought about by random  
 genetic drift, gene flow and especially natural selection
 3. Most adaptive changes are gradual
 4. Diversification comes about by speciation, which ordinarily entails the gradual 
 evolution of reproductive isolation among populations
 5. These processes, continued for sufficiently long periods, give rise to changes 
 of such great magnitude as to warrant the designation of higher taxonomic levels.

Today's evidence of evolution

I. Fossils - relics or impressions of organisms from the past, preserved in rock.

    A. Fossils most frequently form from:

. organisms with hard parts - shells (Image), bones (Image) and (Image), exoskeleton

. organisms that are quickly buried in mud or sand (forms sedimentary rock)

. organisms trapped in amber (Image)

. Many of the parts found have been hardened by petrification, which occurs when minerals dissolved in groundwater seep into the tissues of dead organisms and replace organic matter. (Image)

. other fossils are replicas, casts from molds left when corpses were covered by mud or sand.

. tracks (Image) and coprolites

    B. Paleontology - the study of fossils.

    C. Aging bones and rocks

1. Relative Dating

    - Law of superimposition

- Transitional forms or missing links (Fig 13.3)

    - Eras, periods within each era, and epochs within periods. Each marked by a large extinction episode. Geologic time table.

2. Absolute Dating

radioactive dating.

        - Radioactive isotope

        - Half-life

        - Carbon14 (Carbon 14 degrades to nitrogen 14, but the comparison is done with carbon 12, which is stable)

        - Potassium-40 (degrades to calcium 40, then to argon 40)

II. The Molecular Record

    A. Universal genetic code - all consist of nucleotides with only 4 possible nitrogenous bases

    B. Protein's amino acid sequences. Fig 17.7

        Ex: cytochrome c (Fig 17.8)

    C. Comparison of DNA sequences or amino acid sequences of proteins between organisms

    D. Can use this data to construct phylogenetic trees

III. The anatomical record

A. Development/Embryology - Fig. 17.4 and another image

    B. Homologous structures - Fig 17.5

    C. Homoplastic (analogous) structures result from convergent evolution - Fig 17.6 and Image

    D. Vestigial Structures Image 1 and image 2

IV. Patterns of distribution/biogeography

    A. Organisms on islands most closely resemble forms on nearest continent

        Forms not identical, but diverged over time

        Example: Galapagos finches (Fig. 2.10)

    B. Earth is 4.6 billion years old

    C. Continental drift and plate tectonics (Fig. 25.3) image caused by - convection cells in the mantle (image) similar to those in boiling water (Image)

        Pangaea, Gondwana, Laurasia

Interesting Links:

A simple but interesting look at the origin of the earth and life from NASA.

Videos from PBS you can watch online: http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Visit any time period at the Berkeley site. Lots of good pictures.

Talk Origins

Evolution