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Charles Darwin Erasmus Darwin Zoonomia, Erasmus Darwin Robert and Susannah Darwin Darwin’s Beetles While on the Beagle, 1831-36 The idea of deep time is already broached, and Darwin is thinking along this wavelenght: Jemmy Button & Fuegia Basket Emma Wedgwood Darwin’s Pigeons Anne Darwin Alfred Russel Wallace The Origin of Species, 1859 Great Chain of Being Darwin’s Tree of Life (“entangled bank”) Paley’s argument from design In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there: I might answer, that, for any thing I knew to the contrary, it had lain there for ever. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer which I had before given—that, for any thing I knew, the watch might have always been there. For when we come to inspect the watch, we perceive that its several parts are framed and put together for a purpose. This mechanism being observed, the inference is inevitable, that the watch must have had a maker. The machine which we are inspecting demonstrates, by its construction, contrivance and design, and there cannot be design without a designer; contrivance, without a contriver. The earth is such a contrivance, a watch writ large, and its marvelous design (herein detailed) proves the existence of a Designer. Paley’s argument from design (continued) Nor ought we to feel our situation insecure. In every nature and every portion of nature which we can descry, we find attention bestowed upon even the minutest parts. The hinges in the wings of an earwig and the joints of its antennae, are as highly wrought, as if the creator had had nothing else to finish. We see no signs of diminution of care by multiplicity of objects, or of distraction of thought by variety. We have no reason to fear, therefore, our being forgotten, or overlooked, or neglected. – Wm Paley, Natural Theology Look how much providential care has been bestowed on this seemingly insignificant creature: Darwin’s counterargument It is derogatory that the Creator of countless systems of worlds should have created each of the myriads of creeping parasites and slimy worms which have swarmed each day of life . . . on this globe. The creation and extinction of such forms is the effect of secondary means. --Charles Darwin, Correspondence What Darwin has in mind: Traditional outlook • Young earth—Creation occurred between 6,000 and 10,000 years ago. • All species brought into existence at the Creation and thereafter fixed (unchanging). • Species don’t go extinct. The extinction of species would reflect badly on God’s workmanship at the Creation. • God is intimately involved in nature. God is providential—He attends to the smallest details of nature, and, by implication, the smallest details of our lives. • Humankind, made in God’s image, is discontinuous with other species (which are not made in God’s image). Evolutionary outlook • Old earth—because evolution is a slow process. (Now the earth is said to be about 4 ½ billion years old.) • Species change and pass in and out of existence. • God probably not intimately involved in nature. If He exists, His role was more likely that of setting up laws that now govern nature. Therefore, no divine intervention. • Humankind might well be continuous with other species, since (as Darwin put it) all species originated from a few or even one life form. The “tangled bank” metaphor, all species interconnecting back in a profuse, nonlinear fashion to a primary root, replaces the “great chain of being” metaphor that arranged life forms as discrete and fixed categories in a hierarchy that reached from primitive life forms up to humankind. Unsettling to many people: If we choose to let conjecture run wild, then animals, our fellow brethren in pain, disease, death, suffering and famine—our slaves in the most laborious works, our companions in our amusements—they may partake [of] our origin in one common ancestor—we may all be melted together. —Darwin, one of his notebooks Animals can be our friends, and, like humans, may have heroic qualities: Several years ago a keeper at the Zoological Gardens showed me some deep and scarcely healed wounds on the nape of his own neck, inflicted on him, whilst kneeling on the floor, by a fierce baboon. The little American monkey, who was a warm friend of this keeper, lived in the same compartment of was dreadfully afraid of the great baboon. Nevertheless, as soon as he saw his friend in peril, he rushed to the rescue, and by screams and bites, so distracted the baboon that the man was able to escape. Darwin, Descent of Man Darwin’s teleology Hence we may look with some confidence to a secure future of equally inappreciable length [as the Silurian epoch]. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection. --Charles Darwin, Origin The tangled bank metaphor It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. –Charles Darwin, Origin The closing sentence There is a grandeur in this view of life, with its several powers, having originally been 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. –Charles Darwin, Origin Darwin’s theory of Natural Selection • • • • • Variation of domesticated organisms. Human agents selectively breed flora and fauna to produce certain physical traits, and this breeding brings about immense variation. By analogy, nature is an agent of selection, and since no two individuals have exactly the same characteristics, there is variation in nature. This variation is the raw material upon which Natural Selection operates. Natural Selection will decide which variation is beneficial and which is harmful. We live in a Malthusian world, one in which living populations outstrip available resources; as a result, there is a fierce struggle for existence among individuals and among different species. Survivors of this struggle are those whose variations put them at an advantage, and since much of this variation is inherited, progeny will continue to enjoy the advantages associated with the variation. Over many generations, this process of Natural Selection leads to a continuing gradual change of populations (i.e., to evolution) and to the production of new species. What is a Malthusian world? Critical question: should England enact “Poor Laws”? More poetically: “Nature red in tooth and claw.” 1st Objection Karl Popper, a noted philosopher of science, argued that Natural Selection was a poor scientific theory because it is not, in principle, falsifiable. That is, evolutionary biologists can’t find ways to make predictions whereby the theory can be proved or disproved. It always explains things ex post facto (after the fact), and unlike, physics or chemistry, can’t predict future events (except, perhaps, in very vague ways reminiscent of astrology or Freudian dream theory). Is this a fair objection? 2nd Objection Some people have argued that Natural Selection violates the second law of thermodynamics, which asserts that order in a closed system never spontaneously increases—it always decreases. Is your bedroom self-organizing? No, it gets messy and that’s because it obeys the second law. But Natural Selection posits self-organizing systems that become more complex (more orderly) over time. What about this objection? 3rd Objection Some people argue that while micro-evolution (small changes within a species from generation to generation) is an observable fact, no one has ever seen macro-evolution (the production of a completely new species). Such is always inferred from the fossil record, which is hardly as complete and as trustworthy as we are often led to believe. Any thoughts here? 4th Objection As outlined by Darwin and others, organic evolution is a matter of survival, but human beings have done much more than just survive: they have created language, music, mathematics, art, science, and so on. This seems like so much more than mere adaptation to changes in the environment. In considering this issue, Alfred Russel Wallace (with whom Darwin shared the credit for Natural Selection) proposed that while the human body has come about through a long evolutionary process, not so the human mind or soul: it is a gift from God and the reason we can invent language, music, mathematics, etc. Darwin disagreed.