On the Origin of Species 852


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When I teach On the Origin of Species, I follow a trajectory that is indicated on the powerpoint. I also make sure that students get the background for evolutionary biology. In 2009 to 2010, I used the powerpoint to emphasize the Dialogues with Darwin project that I did along with some IH faculty with the American Philosophical Society. (See preceding powerpoint.)

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On the Origin of Species 852

  1. 1. On the Origin of SpeciesUnderstanding Charles Darwin’s Famous Study Bertolino--Origin of Species--Mosaic 852 1
  2. 2. What is Evolution?• Evolution under the influence of natural selection leads to adaptive improvement. Evolution, whether under the influence of natural selection or not, leads to divergence and diversity. From a single ultimate ancestor, many hundreds of millions of separate species have, at one time or another, evolved. the process whereby one species splits into two is called speciation. Subsequent divergence leads to ever wider separation of taxonomic units – genera, families, orders, classes, etc. Even creatures as different as, say, snails and monkeys, are derived from ancestors who originally diverged from a single species in a speciation event.• http://www.bbc.co.uk/education/darwin/leghist/dawkins.htm• This paragraph, taken from an article by Richard Dawkins, can give us a sense of what The Origin of Species did for modern science and ultimately, the modern conception of man’s origin. Bertolino--Origin of Species--Mosaic 852 2
  3. 3. Bertolino--Origin of Species--Mosaic 852 3
  4. 4. Charles DarwinLife and Times• fifth child of a wealthy, liberal English family with a long line of famous ancestors• graduated 1825 from the elite school at Shrewsbury• entered University of Edinburgh to study medicine• entered the University of Cambridge with the goal to become a priest in the Church of England, however, he became interested in nature, geology and biology and learned all about scientific study, observation, data recording and analysis from his professors Adam Sedgwick and John Stevens Henslow,• After graduating from Cambridge in 1831, Darwin hired aboard the British survey ship HMS Beagle in order to participate in a scientific expedition around the world. Bertolino--Origin of Species--Mosaic 852 4
  5. 5. Darwin…• The expedition, expected to take two years, took five years .The ship traveled around the world (see maps on next slides)• During the expedition, Darwin made discoveries about – Geology and how the earth was formed (uniformitarism vs. catastrophism) – Biology and Biogeography (natural variation and adaptation) – The Origin of Species and Anthropology (survival of the fittest, evolution)• After returning in 1836, Darwin spent almost 20 years analyzing the data he collected and writing up the results.• He lived outside London, was married to Emma Wedgewood and had 10 children. Because of his wealthy background, he was able to study without the necessity to earn a living.• He first announced his theories in 1858 and published the On the Origin of Species in 1859. His book was an immediate success. Bertolino--Origin of Species--Mosaic 852 5
  6. 6. Darwin…Darwin spent the final 23 years of his life expanding on different aspects of problems raised in the Origin. His later books-including - The Variation of Animals and Plants Under Domestication (1868) - The Descent of Man (1871) - The Expression of the Emotions in Animals and Man (1872)• The importance of his work was well recognized by his contemporaries, yet many of his ideas were heavily contested and some debates continue into the present.• He died in Downe, Kent, on April 19, 1882 and was buried in Westminster Abbey Bertolino--Origin of Species--Mosaic 852 6
  7. 7. Darwin’s Influences• Aristotle: Plato believed that Ideas or Forms constituted matter; physical objects came from a permanent essence in thought that determined their existence. Aristotle saw matter as the fulfillment of a physical idea—the form constitutes the concept. He looked at the world as it was--Aristotle saw ultimate reality in physical objects, knowable through experience. Objects, including organisms, were composed of a potential, their matter, and of a reality, their form; thus, a block of marble -- matter -- has the potential to assume whatever form a sculptor gives it, and a seed or embryo has the potential to grow into a living plant or animal form. In living creatures, the form was identified with the soul; plants had the lowest kinds of souls, animals had higher souls which could feel, and humans alone had rational, reasoning souls. In turn, animals could be classified by their way of life, their actions, or, most importantly, by their parts.• Great Chain of Being—the order of things. The world has a spiritual hierarchy that extends from the lowest physical creature to the supernatural (amoebas to the archangels with intellectual abilities that are superior to our own.) This theory illustrated that God’s omnipotence included other planets that possibly had spiritual beings—it was a continuum of life that never ended, like a ladder into the heavens from the earth. Bertolino--Origin of Species--Mosaic 852 7
  8. 8. Other Influences• Jean Baptiste Lamark (1744-1829)—all forms of life have arisen through a long process of continuous adjustment. Nature had an instinctive sense for improvement; each living creature, plant and animal, moved to a higher stage of development. The environment proved to be a factor in these movements toward change: the dictates of nature caused animals, plants to modify their features in order to survive. These same changes would move on to the subsequent generation.• Thomas Malthus ((1766-1834)—Populations tend to increase geometrically while food supplies increase arithmetically. Malthus was an economist who discriminated against any social welfare: he connected population growth with food abundance and he believed that this correlation was natural in order to maintain population growth from exceeding the natural sustenance that our world could give. Disease, famine and human conflict are modes to control population in accordance with nature. If we continue to use social reforms to help the poor, we will interfere with nature’s plan to maintain human survival as God intended it to be.• Darwin disagreed with this laizzez-faire cruelty, yet it gave him the basis of his theory of natural selection. Bertolino--Origin of Species--Mosaic 852 8
  9. 9. Voyage of the Beagle—Various Aspects:Full View Bertolino--Origin of Species--Mosaic 852 9
  10. 10. Travels Through South America: Atlantic Side Bertolino--Origin of Species--Mosaic 852 10
  11. 11. Brazil—Upper South America Bertolino--Origin of Species--Mosaic 852 11
  12. 12. ArgentinaBertolino--Origin of Species--Mosaic 852 12
  13. 13. Darwin’s Discovery in ArgentinaDarwin was very curious about the geology of the river valley.The walls of the valley had the same layers of shells he had seenmany times before. It was during this expedition that Darwintheorized that the cliffs of the river valley, and indeed the AndesMountains themselves, had been slowly raising above sea level.The evidence for a planet in a state of constant flux wasbecoming stronger and stronger. While today we take this forgranted, in Darwins day the notion of changes on a planetaryscale went against the view that gods creation was perfect andthus change was Bertolino--Origin of Species--Mosaic 852 unnecessary. 13
  14. 14. The Beagle Travels Past Cape HornDarwin made some of his most importantdiscoveries on the Pacific side of SouthAmerica. Bertolino--Origin of Species--Mosaic 852 14
  15. 15. To Mocha Island off The Mainland of ChileOn March 4th the Beagle entered the Harbor of Talcuhano near Concepcion.Darwin was dropped off at the island of Quiriquina. Here he explored aroundthe coastline of the island and found several expanses of fresh marine rockthat had risen a few feet above sea level due to an earthquake. Darwin alsonoticed raised shell beds on the cliffs above and became very excited aboutthis find, as it was direct evidence that the Andes mountains, and indeed all ofSouth America, may be very slowly raising above the ocean.These discoveries added much weight to Charles Lyells theory that land massesrose up in tiny increments over extremely long periods of time. Darwin acceptedthe idea that the earth must be extremely old. The next day Darwin went byship to Talcuhano Harbor. From the shore he rode by horse to the town of Bertolino--Origin of Species--Mosaic 852 15Concepcion.
  16. 16. Another Discovery Along the Mainland of Chile• Darwin head back, on March 29th, to Chile via the Uspallata Pass, just north of Mendoza. He spent the next few days at Villa Vicencio and explored the geology of the area. He was shocked to find that the local mountains were mainly composed of submarine lava flows, and these at 6,000 feet above sea level and 700 miles from the coastline! Eleven trees had been fossilized and 30-40 had turned into calcareous spar. Most of the trees were a few feet tall and snapped off at the top and 3-5 feet in circumference, and were coniferous.• To make matters even more confusing for Darwin, he also found huge numbers of petrified trees in the same area. His mind was reeling with questions: how long ago was this land under the ocean, how did the trees end up under water so they would become petrified? Darwin spent the next few days thinking about how Charles Lyell would interpret what he was seeing and also began developing some geological theories of his own. Bertolino--Origin of Species--Mosaic 852 16
  17. 17. Up the Andes Mountain Range and ToThe Galapagos Bertolino--Origin of Species--Mosaic 852 17
  18. 18. Darwin’s Discovery:Some of the specimens Darwin collected from the Galapagos:One buzzard, two owls, three flycatchers, three species of mockingbirds,one species of finch, one swallow, one dove, 13 species of finches (Darwinremarked how fascinated he was by the beak gradations, but the variationof finches confused Darwin a great deal), one turtle, one tortoise, fourlizards (sea and land iguanas and two other types), four snakes, and veryfew insects.These specimens helped Darwin come up with theories of reproduction: whydo finches have such a variety of beaks? Do they breed different beaks to Bertolino--Origin of Species--Mosaic 852 18determine their rate of survival?
  19. 19. Variation of Finch Beaks and the Geological Table Bertolino--Origin of Species--Mosaic 852 19
  20. 20. The Beagle Travels to the South Pacific,Visiting New Zealand, Tahiti and Australia.New discoveries are made. Bertolino--Origin of Species--Mosaic 852 20
  21. 21. Darwin’s Discovery: Darwin went with a guide and two horses on a 120 mile inland trip toBathurst, New South Wales. Darwin commented on the scantvegetation, and contrasted it with the tropical forests of SouthAmerica. Along the way Darwin made observations on the localwildlife and was very astonished by the creatures he saw (especiallythe odd-looking platypus). He surmised there must have been aseparate act of creation just for these odd creatures.Again, he mused on the role of reproduction and adaptation: how doliving things change in different climates? Do they take on new traits(adapt) in order to survive the climate changes or do many die off while Bertolino--Origin of Species--Mosaic 852 21other life begins to thrive?
  22. 22. The BeagleDarwin spent 5 years on this ship and his discoveries radically changedhis views on the origin of organic life. Bertolino--Origin of Species--Mosaic 852 22
  23. 23. Questions to Consider1.What point does Darwin prove with his ideas on Variation underDomestication? Which examples does he use?2.What is the difference between domestic and natural variation?3.What is the underlying process of explaining natural variation asopposed to controlled variation? (See “Variation under Domestication”and compare it to “Struggle for Existence” in the text.)4.What examples of adaptation does Darwin use? How can this theorybe used to explain the fact that the dinosaurs became extinct?5.What are the long term implications of natural selection for thedevelopment of humanity? Bertolino--Origin of Species--Mosaic 852 23
  24. 24. Summary of First Four ChaptersCh. 1 Variations under Domestication: Darwin uses examples such as horses, dogs, or pigeons, to prove that with careful selection, consequent breeding it is possible to bring out intended characteristics.Ch.2 Variations under Nature: Darwin discusses the possibility that selection also occurs in nature, just slower than with domestic breeding. The issue here is adaptation to the corresponding natural environment that causes this amazing variability. Yet, one question remained: Why do these variations occur?Ch.3 The Struggle for Existence: Day to day existence is a constant struggle that ensures that selection will occur. Those less able to adapt and thereby survive will reproduce and pass on the traits that made survival possible. In this way, nature ensures that only the fittest survive the process he terms… Bertolino--Origin of Species--Mosaic 852 24
  25. 25. Natural Selection—Chapter 4Ch. 4 Natural Selection. Natural selection explains, why certain species survive and thrive, others, less able to adapt, become extinct. Natural selection, however, also supports the notion of a slow process of adoption and survival. The result is a successive evolution and improvement of a species, and not a sudden creation of each individual species. The intriguing thought behind this is that there is an ongoing process of evolution from one particular ancestor to a variety of succeeding subspecies. There is additionally, a variety of subspecies that have not succeeded (reproduced over time) and eventually they become extinct.• Question: What factors determine which species will survive and which one will die off?• Question: How do you understand the word “selection”?• Question: How do you understand the word “natural”? Bertolino--Origin of Species--Mosaic 852 25
  26. 26. Ideas from Chapter 1• Immutability vs. Variation under Nature—Does the world change?• Darwin’s observations of nature suggest that the earth is very old. Geologists in Darwin’s lifetime (Charles Lyell) had studied fossils and worked on theories that different fossils represent different time periods in earth’s history. Creationists called this a part of God’s plan.• Darwin considered the sea cliffs on the Galapagos Islands: they suggested that the water level gradually receded from a previous point. He found well-formed shells imbedded in the cliff—he hypothesized that the cliff had once been under water. The change couldn’t have been cataclysmic or else the shells would not have been intact.• Darwin discussed the intent of animal breeders who use unconscious selection, a method of matching like traits in order to produce a certain kind of animal. Consider how certain race horses are used as studs—similar idea. These ideas come from “Variation Under Domestication.” Bertolino--Origin of Species--Mosaic 852 26
  27. 27. Adaptation: A Part of Natural Selection• Variation among plants and animals—does the reproduction of like traits occur in nature?• Darwin theorized that living creatures unconscious adapt in order to survive. Adaptive traits are reproduced; non-adaptive ones decrease in number over time.• He looked at domesticated pigeons as an example. He couldn’t believe that man bred seven to eight species of the domesticated pigeon; he concluded that they came from a wild state that was eventually tamed. Later he wrote that “changed conditions of life are of the highest importance in causing variability, both by acting directly on the organization, and indirectly by affecting the reproductive system.” Variation, he believed, “is governed by unknown laws of which correlate growth….something…may be attributed to the …conditions of life. Some…may be attributed to the increased use of disused parts.” Bertolino--Origin of Species--Mosaic 852 27
  28. 28. The Struggle For Existence Darwin understood this as both the individual struggle and the success of reproduction. He called it “ the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms….although some species may now be increasing…all cannot do so, for the world will not hold them.”• Members of a variety with adaptive traits live longer and have more time to reproduce, thus adaptive traits become dominant in a particular environment. Modification of a variety occurs when there is a change that results in better environmental adaptation. Beak, web sizes may alter; certain plants may develop a different way to seed— these are adaptations that modify the species. These traits continue as the creature reproduces to insure survival. This entire process over time is called natural selection. If man can cause unconscious selection through breeding, then why cannot nature do the same? He argues that “natural selection acts only by the preservation and accumulation of small inherited modifications, each profitable to the preserved being”. He believes that the elements of natural selection: physical alterations, reproduction, and intercrossing take place over long periods of time. All of these are a response to the demands of the environment. Bertolino--Origin of Species--Mosaic 852 28
  29. 29. Chapter 6: Difficulties of Theory• This chapter only appeared in the 6th edition to answer various doubts about the theory.• He focused on natural selection, breaking it down from species to species.• He relied heavily on the samples he had found from his journey on the Beagle.• He discussed creatures, like the flying lemur— falsely classified as a bat. The flank membrane gave him reason to think that the lemur once had a longer membrane that connected fingers and forearms, disused through reproduction over time. Bertolino--Origin of Species--Mosaic 852 29
  30. 30. Chapter 7: Instinct• The closest Darwin comes to defining the term instinct is the following: “An action, which we ourselves (humans) should require experience to enable us to perform, when performed by an animal, more respectively by a young one, without any experience, and when performed by many individuals in the same way, without their knowing for what purpose it is performed, is usually said to be instinctive.” (paragraph 2 of Chapter 7) Bertolino--Origin of Species--Mosaic 852 30
  31. 31. To illustrate what he calls instinct in a “state of nature”, Darwin uses bees—hive bees. Then he focuses on ants in great detail.• Why are the worker ants rendered sterile? What modifications within reproduction are they instinctively not supposed to pass on? Darwin sees this as natural selection.• Darwin looks at time: he writes: “As natural selection acts only by the accumulation of slight modifications of structure or instinct, each profitable to the individual under its conditions of life, it may reasonably be asked, how a long and graduated succession of modified architectural instincts, all tending toward the present plan of construction, could have profited the progenitors?” (Chapter 7, section on bees) In this sentence, Darwin is referring to the hive bee, but it is also applicable to all species in their struggle for survival. Bertolino--Origin of Species--Mosaic 852 31
  32. 32. • Evolution postulates that new species are descended fromChapter 9: On the earlier species, which changed into those new species over periods of time. Evolution thus predicts that there wereImperfection of the organisms which existed at these transitional stages turning from one form into another. It is possible that evidence ofGeological Record these evolutionary transformations may be found in the fossil record. This was noted by Darwin: “The number of intermediate varieties, which have formerly existed on the earth, [must] be truly enormous.”( paragraph 1 of Chapter 9) • However, Darwin recognized that the fossil record did not contain fossils of these "intermediate" forms of life and he struggled to understand the reason: • “We continually forget how large the world is, compared with the area over which our geological formations have been carefully examined; we forget that groups of species may elsewhere have long existed and have slowly multiplied before they invaded the ancient archipelagoes of Europe and the United States. We do not make due allowance for the enormous intervals of time which have probably elapsed between our consecutive formations— longer perhaps…that the time required for …each formation.” (Chapter 9) • In other words, Darwin staunchly believed that his theory was correct, so he took issue with the presentation of the geological record (fossils, timeline) as an incomplete process that missed certain evidence of life—species that developed and declined without leaving a record of their existence. Bertolino--Origin of Species--Mosaic 852 32
  33. 33. Bertolino--Origin of Species--Mosaic 852 33
  34. 34. Bertolino--Origin of Species--Mosaic 852 34
  35. 35. The Gradual Change or Adaptation ofSpeciesDarwin was convinced the transition of species tookplace. He suggested a process—look at the circledshapes above and imagine them to be reproductive traitsthat are discarded or strengthened over a long period of Bertolino--Origin of Species--Mosaic 852 35time.
  36. 36. Bertolino--Origin of Species--Mosaic 852 36
  37. 37. Chapter 11—Geographical Distribution• In this chapter, Darwin explores species migration. Why do pigeons survive in multiple climates, while elephants are only found in warm climates? Why do some species seem to travel and form subspecies while others remain exclusive to a particular territory?• Darwin writes: “I believe…in no law of necessary development. As the variability of each species is an independent property and will be taken advantage of by natural selection, so the degree of modification in different species will be no uniform (standard) quality.” (Chapter 11)• So the process of natural selection allows for migration-in other words, it is part of the adaptation process for some species to seek out other environments; it is also crucial for other species to remain in the place of their origin—this insures the survival of the species and subspecies in both cases.• Some of this is intuitive—think about instinct from chapter 7. Some of this is also reliant on how a particular species travels—birds fly, fish swim, so it can be easier for them to travel than certain mammals. However, certain birds and fish cannot survive in different climates. So the process of natural selection determines both the impulse to migrate and the necessary adaption to various climates. The animals that cannot survive elsewhere will stay put. Bertolino--Origin of Species--Mosaic 852 37
  38. 38. Drawings of possiblemigrationsThe first images shows various speciesthat Darwin found in the Galapagosduring his voyage on the Beagle.The second drawing shows ahypothesis of Darwin’s theory ofspecies evolution through the processof migration. Macroevolution coversthe movement/adaptation of animaland plant life in their entiretyMicroevolution shows the changesover time within each species. Forexample, are tortoises the originalspecies for what we call the commonturtle? If so, how did turtles end up inthe Northern Hemisphere? Are they asubspecies of the Pacific tortoise? Howdid the turtle evolve as a subspeciesand why does it live in coolerclimates?. Bertolino--Origin of Species--Mosaic 852 38
  39. 39. More on Migration• Darwin writes: “If, for instance, a number of species, which stand in direct competition with each other, migrate in a body into a new and isolated country, there will be little liable to modification, for neither migration or isolation can do anything. These principles come into play only by bringing new organisms into new relations with each other (the life forms that exist in the place of migration—my note).”• Darwin writes: “It is obvious that the several the several species of the same genus, though inhabiting the most different quarters of the world, must originally have proceeded from the same source as they have descended from the same progenitor.”• Darwin came to these conclusions largely from his study of finches and pigeons. (see slide 19) Bertolino--Origin of Species--Mosaic 852 39
  40. 40. Conclusion of Text—Chapter 14• John Whitfield, a science writer from England wrote the following on Chapter 14: “As its title suggests, the fourteenth and final chapter of the origin, Recapitulation and Conclusion, mostly restates things that Darwin has already said, often several times.”• “This relentless piling, sorting and re-arranging of evidence can make Darwin seem a little OCD, like an intellectual version of Wall- E. But he also knows that beneath all the case studies, theres a logical core to evolution by natural selection, even if he cant put it in an equation. Darwin brackets this chapter by showing that, if you accept the most basic evidence the living world puts before your eyes, evolution follows as surely as a lever moves a stone.”• “And as the reader lowers the book, it points him or her outward. Evolution isnt an abstraction, its not just something you see on the Galapagos Islands. Its going on right now, all around you. This is how you see the world now.” Bertolino--Origin of Species--Mosaic 852 40
  41. 41. As Darwin Puts It:• “Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. “• “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. “(Chapter 14) Bertolino--Origin of Species--Mosaic 852 41
  42. 42. Bertolino--Origin of Species--Mosaic 852 42
  43. 43. EpilogueIntroduction to Social Darwinism(present at the APS exhibit) Marx was greatly influenced by Darwin and he respected his ideas. He wantedto dedicate his major work, Das Kapital,to him, but Darwin refused the honor.Marx misunderstood the theory of natural selection as a method tomanipulate the means (mode) of production so that the exchange ofcommodities would benefit workers in a communist society. Marx wanted to recreate the entire economic model (capitalism) intocommunism: he thought that natural selection would work as a force toimprove man as a species, so it was logical to assume that the next step forman’s survival would be to throw off the chains of wage slavery as a necessarystep in his evolution. Darwin saw this as a misreading of his theory.One result of Darwin’s Origin of Species was Social Darwinism. This ideacame from Herbert Spencer’s term, survival of the fittest. Darwin used thisterm to name the process of natural selection in nature as living creaturesstruggle for their existence. These beings develop variations that grant them anadvantage as they compete for food and shelter. Darwin saw this as anunconscious tool of nature. Bertolino--Origin of Species--Mosaic 852 43
  44. 44. What is Social Darwinism?• Social Darwinism: literally a process of elimination in a capitalist society. The strong adapt to the rigors of the free market system and the poor decline. Society must coexist as a unit, similar to the creatures in a jungle, and each person takes on traits to ensure his survival. Ultimately, it promotes the group that has the dominant traits that lead it to take over their environment. This theory became the basis for some of the most heinous acts in history: it was used to justify ruthless business practices of the industrial tycoons, the conquest of the Americas, the genocide of Native Americans, Imperialism in countries like India, Vietnam, and much of Africa. Perhaps the most odious example is Nazism:• Ernst Haeckel, a 19th German biologist, used the Origin of Species to assert his vision of the German people as a superior race. He believed that nations had to fight to survive as organisms did or they would perish. Society must be ruled by the same laws of competition and aggression that are found in nature. Individual life was unimportant. The Jews, Gypsies, Africans and Slavic people were inferior. Heinrich Himmler admired Haeckel and formed an Aryan youth movement in 1918.• (His work was featured in the APS exhibit along with Eugenics, an offshoot of Darwin’s research into heredity and genetics. Note: these terms came AFTER Darwin’s death.) Bertolino--Origin of Species--Mosaic 852 44
  45. 45. Design For Darwin Birthday Cake Bertolino--Origin of Species--Mosaic 852 45