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Charles Darwin and the Voyage of the Beagle Psalm 104:24-30 O LORD, how manifold are your works! In wisdom you have made them all; the earth is full of your creatures. Yonder is the sea, great and wide, creeping things innumerable are there, living things both small and great. There go the ships, and Leviathan that you formed to sport in it. These all look to you to give them their food in due season; when you give to them, they gather it up; when you open your hand, they are filled with good things. When you hide your face, they are dismayed; when you take away their breath, they die and return to their dust. When you send forth your spirit, they are created; and you renew the face of the ground. What was the motivation for a “new explanation”? • Discuss with your neighbor and generate some suggestions for each of the following… – What was the current, widely held notion of “origins”? – What shortcomings did the prevailing idea(s) have? Overview • By the early 19th century, many of the basic concepts necessary to develop a scientific explanation for the diversity of life on Earth were in place: – Ancient Earth (James Hutton millions years old earth) – Extinction of species as represented in fossils (immutable) – Similarity (continuity) of species (Ray & Linnaeus) – No mechanism was available to explain how species could change over time – Most if not all “ men of science” were convinced that organisms had descended through inheritance from previously existing organisms. Words from Dr. Strohmeyer… • An obvious or veiled argument is often made that religion (Christianity being the main target and lumped in with all religions of every type as being the same and thereby mythical) and it’s accompanying theological/philosophical views were wrong and a negative influence in various ways. • Many evolutionists will claim to be scientific and unbiased but in reality science exists only because there is a “philosophy of science”—a means for defining what constitutes science. Thus no one does anything (including science) without a worldview bias. And for current science the philosophy of life (worldview) is naturalism and its accompanying subisms. – So a word of caution, just because a textbook in a course makes certain claims, doesn’t mean these claims are true. Academic people write textbooks, often later in career and are largely secular and liberal in their worldviews. SO BE DISCERNING as you learn! There is truth and there is untruth. Guard your mind and choose your truth by checking it against scripture and in prayer!!! Theodosius Dobzhansky • “Nothing in biology makes sense except in the light of evolution”. • How would you define “theory”? – Biological evolution is called a theory because … – The theory of evolution provides… Theodosius Dobzhansky, ca.1966 3 important questions remained: 1. How were species to be regarded? 2. What natural cause or mechanism could explain organismal change? 3. What hereditary mechanism could enable new species to arise? • Q1 - Could not be resolved by Darwin and others of his day. Why not? • Q2 - Darwin provided a theory for organismal change based on evolutionary biology (dysteleological)—as opposed to various design (teleological) hypotheses of the day—i.e. William Paley. • Q3 - was addressed in part in Darwin’s day by Gregor Mendel but his work remained undiscovered (not understood) for another 40 years. Fossils • An essential basis for understanding evolutionary relationships • Various views on Fossils – 16th-17th Centuries– “stones” images of God’s creation, placed on Earth for man’s admiration and use but formed naturally by God—body parts displays/models. – Errors in the plan of nature, causing some species to become extinct? For them fossils were lusi naturae (“ jokes of nature”). – Thomas Jefferson and many others proposed that fossil species were not really extinct, only rare. (not completely wrong— living fossils are known) Fossils • Various views on Fossils (cont.) – Caused by the Noachian flood described in Genesis. – Purposely implanted into Earth at the time of creation in order to test humanity’s faith in religion. • Contrary arguments proposed the reality of fossils and led to more naturalistic attempts to understand fossil origins. – George Cuvier saw that fossils from younger rocks were more like living organisms than were fossils from older rocks— stratigraphy. Fossils • In Darwin’s day, the fossil record was sporadic, the result of serendipitous collecting and random finds. While more concerted efforts have since been made, • The fossil record is still considered incomplete for a variety of reasons. – What reasons do you suggest? *Decomposition *Erosion *Sympatric speciation more rare?!? *Soft-bodies *Geological processes *Many fossils are still buried… (yet to be discovered) Stratigraphy Fossils • A complete evolutionary progression of fossils from most ancient to most recent has never been found in a single locality. • Nevertheless, fossils provide the hard evidence for evolution, evidence used by Charles Darwin who first offered an acceptable explanation for historical changes among organisms and thereby helped tie all organisms together by a community of descent: evolution. Fishapod (Tiktaalik roseae) Illuminates steps leading to evolution of tetrapods from fish—explanation level Had broad skull, flexible neck, eyes on top, interlocking rib cage suggesting lungs, pectoral fins resembling primitive wrist and 5 finger-like bones—basic fact level Peek above water and look for prey—pure speculation with no real way of knowing 13 Defining Species • Plato – Idealism – Organisms’ imperfect representations of essence – A form of teleology/design is the archetypetype • Aristotle – Great Chain of Being – Species immutable – Hierarchical order of imperfect perfect (also teleological— ascent towards perfection) • Leibnitz – gaps in “chain” suggest evolution towards perfection. Proposed that universe was imperfect and that it and all in it was evolving towards perfection-major philosophical shift. • Bonnet – Preformationism—homunculus, teleology – Unfolding of preconceived plan in embryo into perfect adult Classification of Species • Classification schemes of many types made defining and organizing species a VERY difficult task. • Mid- to late-1600s, John Ray was the first to carry out a thorough study of the natural world – Developed an early classification system – Modern species concept • Extended by Carolus Linnaeus (1707-78) – Binomial nomenclature: genus species – Still believed in species constancy, dismissing evolutionary transformation and was ardently idealistic and teleological • Neither proposed that evolutionary change promotes the formation of new species Biological Importance of Species • Late 1700s, small number of European scientists suggest life forms are not fixed • Buffon (1707-1788) – Life forms change over time – Defined species by ability to reproduce fertile offspring – Natural barriers to species possible "reproductive isolation" – Variation within a species accepted through a degenrative mechanism (genetic entropy of a sort) – Evolutionary transformation still rejected as contrary to religion Classification of Species • Jean-Baptiste de Lamark (1744-1829) – Dismissed fixity of species— recognition of species actually hindered a theory of evolution because species seemed to be fixed. – Proposed branching classification of animals – Animals evolved from each other – Believed living things evolved upward toward human “perfection” – Inheritance of acquired characteristics—somatic inheritance Species Concepts • Morphological species (morpho-type) – Shared similar characters – Special case: Paleontological species—reproductive isolation cannot be determined for fossils, thus not a biological species. In situations in which a set of paleontological species can be identified as representing a series of ancestral and descendant populations, paleontological species also may be recognized as evolutionary species. • Biological species – Cross produces viable offspring – Sexually reproductive species • Evolutionary species – Isolation based on multiple character types Charles Darwin (1809-1882) Figure 1B & 1C: Charles Darwin © National Library of Medicine. • Born to upper middle-class British family • Age 16, Edinburgh University to study medicine • Cambridge University with the intention of becoming a minister of the Church of England • 1831 set sail on the H.M.S Beagle – Not as ship’s naturalist but as captain’s companion Voyage of the Beagle Voyage of the Beagle (1831-1836) • Collected specimens in the Brazilian tropics • Unearthed fossils of extinct species – Discovered fossil bones in Argentina, such as the 6mhigh giant sloth, Megatherium. • Explored the Galapagos Archipelago – Darwin read Lyell's Principles of Geology—promoted uniformitarianism over catastrophism. • Struck by distinctive traits of island species Galapagos Islands • Small volcanic islands off western coast of South America. • Darwin collected many specimens of finch. – He later noted that each island had finches with a unique beak shape. • Tortoises and land iguanas too… Darwin's Finches – Each island has unique beak shape. – Variation in beak shape provides advantages for the food source available on each island. – Beak shape modified, but how? • Natural Selection—what about that Bmp-4 story— rapid beak change by gene regulation rather than gradual genetic change. Darwin’s Influences • Theory shaped by several different fields of study—it was in the air at the time academically speaking – – – – – Grandfather (common descent) Geology—Lyell/Hutton (contemporaries-Lyell friend) Economics—Malthus Biology—Lamarck, Buffon and others Voyage of the Beagle • General academic atmosphere just prior to and during Darwin’s time that began to favor natural explanations. “Would it be too bold to imagine that, in the great length of time since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind would it be too bold to imagine that all warm-blooded animals have arisen from one living filament, which the great First Cause endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions and associations, and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down these improvements by generation to its posterity, world without end!” • Erasmus Darwin (grandfather) • Uniformitarism hypothesis from geology— Lyell/Hutton – Slow recurring geological processes lead to substantial change (i.e. erosion,) rather than catastrophic events – Earth was much older than 6,000 years – Darwin read Lyell's Principles of Geology (influnced by Hutton), and used it to study geological features during the voyage—promoted uniformitarianism over catastophism. 27 • Thomas Malthus, and his essay on economics… • Aided Darwin in his ideas about how natural selection worked via competition and selection and survival of the fittest. 28 After the voyage on The Beagle • Begins to formulate theory of evolution around 1837 and has much of it worked out by mid 1840s • Spent several additional years studying barnacles, perhaps to become an expert in a species. Also studied many other organisms to a lesser extent. • 1856, began writing his book • Why do species change? In seeking an answer over the next 20 years, Darwin explored a variety of theories. – One of the most persistent, a theory that later had many adherents in France and the United States, was most fully developed by Jean-Baptiste Lamarck. We know it as 29 Lamarckian inheritance. Lamarckian Inheritance • Where others had looked at fossils and saw species extinction, Lamarck made the intellectual leap of proposing the continuity of species by gradual modification through time. • By the early 19th century, most naturalists accepted the inheritance of acquired characters, the utility ( adaptedness) of features, and the concept of some internal force toward change. • To explain how modifications occurred and the exquisite relationships ( adaptations) through which organisms exploited their environments, Lamarck is credited with proposing that – variations among organisms originate because of the organisms’ response to the needs of the environment; – this ability to respond in a particular direction accounts for the adaptation of new features and their passage to subsequent generations – Water bird legs, giraffe’s long neck, etc (just-so-stories) Lamarckian Inheritance • Lamarckism – adaptations driven by an inner vital force that helped organism evolve to perfection (simple to complex) by sensing the needs of the new environment and creating new traits that could be passed to offspring. 2 (3) Laws 1. Principle of Use and Disuse. – In every animal that has not passed the limit of its development — like Linnaeus, Lamarck saw organisms as progressing through some internal principle — more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ and gives it a power proportional to the length of time it has been so used. The permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears. Lamarckian Inheritance 2. Inheritance of Acquired Characters – All of the acquisitions or losses wrought on individuals through the influence of the environment, and hence through the influence of the predominant use or permanent disuse of any organ, are passed on by reproduction to the new individuals that arise, provided that the acquired modifications are common to both sexes, or at least to the individuals producing the young 3. Some would list the drive toward perfection as a third process central to Lamarck’s thinking. • By proposing a materialistic explanation for evolution (inheritance of acquired characters), an explanation that reflected the close interactions known to occur between organisms and their environment, Lamarck fostered a climate of opinion in which evolution could be understood in the same fashion as any other natural event. • Many detractors (i.e. Cuvier) and eventually proven incorrect Key Concepts • Darwin explained the relationships between organisms as the result of common descent from a single ancestor. • Darwin proposed a theory of evolution by natural selection (and sexual selection). • The fossil record, the biogeography, and domestication all provided evidence for Darwin’s theories.