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Chapter 2

Textbook Chapter 2 Notes

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University of Toronto Mississauga
Heather Miller

Notes From Reading CHAPTER 2:T HE DEVELOPMENT OF EVOLUTIONARY T HEORY (PGS. 19-36) Learning Objectives  Describe the key contributions to evolutionary theory made by precursors to Darwin and explain how each influenced the development of evolutionary theory  Explain how natural selection works  Contrast the scientific understanding of biological evolution with nonscientific approaches that seek to explain the origins of life and how life has changed on earth Introduction  The earliest human ancestors evolved from a species that lived some 5 to 8 million years ago  The ancestral species was the last common ancestor we share with chimpanzees  The lineage that led to the apes and ourselves separated from a monkey-like ancestor some 20 mya, and monkeys are still around b/c as lineages diverged from a common ancestor, each group went its separate ways  Each living species is the current product of processes that go back million of years  We aren’t able to see evolution since it takes long periods of time, but we do see microevolutionary changes in many species  Evolution is a theory, one that has increasingly been supported by a mounting body of genetic evidence  As physical anthropology is concerned with all aspects of how humans came to be and how we adapt physiologically to the external environment, understanding details of the evolutionary process is crucial A Brief History of Evolutionary Thought  Charles Darwin was the first person to explain the basic mechanics of the evolutionary process  Natural Evolution – the most critical mechanism of evolutionary change, first articulated by Charles Darwin o Refers to genetic change in the frequencies of certain traits in populations due to differential reproductive success between individuals  Alfred Russel Wallace independently reached the same conclusion as Darwin did more or less the same time about natural selection  It was generally accepted that all life on earth been created by God exactly as it existed in the present, and the belief that life-forms couldn’t change came to be known as fixity of species  Fixity of Species – the notion that species, once created, can never change o An idea diametrically opposed to theories of biological evolution  Evolution requires time, and the idea of immense geological time, which today we take for granted, simply didn’t exist The Scientific Revolution  For Europeans, the discovery of the New World and circumnavigation of the globe in the fifteenth century overturned some basic ideas of earth (Ie. The Planet is not flat)  As the Europeans began to explore, their awareness of biological diversity was greatly expanded as the became aware of plants, animals they hadn’t seen before  Later Copernicus challenged the notion of Aristotle (the earth is circled by the sun, moon and stars) o Indian scholars figured out that the sun was the center of the solar system before Corpernicus o Corpernicus is generally credited with removing the earth as the center of all things  Galileo Falilei restated Corpernicus theory later (since at the time it didn’t attract anyone) Precursors to the Theory of Evolution  Scholars were increasingly impressed with the amount of biological diversity they saw John Ray  In the 1700s, developed the concept of species  First to recognize that groups of plants and animals could be distinguished from other groups by their ability to mate with one another and produce offspring Notes From Reading CHAPTER 2:T HE DEVELOPMENT OF EVOLUTIONARY T HEORY (PGS. 19-36)  Placed groups of reproductively isolated organisms into a single category, species  Also recognized that species frequently shared similarities with other species, and he grouped these together in a second level of classification, genus  Was the first to use the labels genus and species (which is still used today) Carolus Linnaeus  Developing a method of classifying plants and animals  Standardized Ray’s use of genus and species  Binomial Nomenclature – in taxonomy, the convention established by Carolus Linnaeus whereby genus and species names are used to refer to species o Homo sapiens refer to human beings  Added two more categories: class and order  Taxonomy – the branch of science concerned with the rules of classifying organisms on the basis of evolutionary relationships Jean-Baptiste Lamarck  Was the first to explain the evolutionary process  Suggested a dynamic relationship between species and the environment changed, an animal’s activity patterns would also change to accommodate the new circumstances  The physical changes would occur in response to bodily “needs” so that if a particular part of the body felt a certain need, “fluids and forces” would be directed to that point and the structure would be modified  Theory is known as the inheritance of acquired characteristics or he use disuse theory o According to this theory, a trait acquired by an animal during its lifetime can be passed on to offspring  It is wrong, only those traits that are influenced by genetic information contained within sex cells (egg and sperm) can be inherited  He coined the term biology to refer to studies of living organisms Georges Cuvier  Introduced the concept of extinction to explain the disappearance of animals represented by fossils  Suggested a variation of a theory known as catastrophism  Catastrophism – the view that the earth’s geological landscape is the result of violent cataclysmic events o This view was promoted by Cuvier, especially in opposition to Lamarck  Curvier needed to account for the emerging fossil evidence that organisms had become more complex over time  He suggested that after each disaster, the incoming migrants had a more modern appearance because they were the results of more recent creation events Thomas Malthus  Wrote An Essay on the Principle of Population, which inspired both Darwin and Wallace in their separate discoveries of natural selection  In his essay, he argued for limits to human population growth o Pointed out that human population could double in size every 25 years  Warned that increased numbers of humans would eventually lead to famine  Darwin and Wallace accepted Malthus’ proposition that population size increases exponentially while food supply remains constant (and all organisms)  What Malthus didn’t realize (whereas Darwin and Wallace did) was the competition for the available resources  Competition between individuals is the ultimate key to understanding natural selection Charles Lyell  Founder of modern geology  Argued that geological processes observed in the present are the same as those that occurred in the past Notes From Reading CHAPTER 2:THE D EVELOPMENT OF EVOLUTIONARY THEORY (PGS. 19-36)  Uniformitarianism – theory that the earth’s features are the result of long-term processes that continue to operate in the present as they did in the past o Elaborated on by Lyell, this theory opposed catastrophism and contributed strongly to the concept of immense geological timeh  Although various aspects of the earth’s surface (ie. climate, plants, animals and land surfaces) are variable through time, the underlying processes that influence them are constant  The concept of “deep time” remains as one of Lyell’s most significant contributions to the discovery of evolutionary principles  The immensity of geological time permitted the necessary time depth for the inherently slow process of evolutionary change The Discovery of Natural Selection Charles Darwin  Had an interest in nature  When to Edinburgh University to study medicine and became acquainted with the evolutionary theories of Lamarck and others  Anything identifiable with post evolutionary France was viewed with suspicion by the established order in England  The Reform Movement, which sought to undo many of the wrongs of the traditional class system, was underway  Many of the radicals were atheists and socialists who also supported Lamarck’s ideas, many people came to associate evolution with atheism an political subversion  Transmutation – the change of one species to another o The term evolution did not assume its current meaning until the late nineteenth century  He realized he hated medicine, so he went to Cambridge to study theology and became interested in natural science, immersing himself in botany and geology  The insight that Darwin gained from the finches is legendary  Recognized that the various Galapagos finches has all descended from a common mainland ancestor and have been modified over time in response to different island habitats and dietary preferences  Darwin began to develop his views on what he called natural selection  Late 1830s, he had realized that biological variation within a species was crucial and sexual reproduction increased variation Alfred Russel Wallace  Became interested in collecting plants and animals  Published a paper suggesting that species were descended from other species and that the appearance of new species was influenced by environmental factors  The Wallace paper caused Lyell and others to urge Darwin to publish, but still he hesitated  Wallace described evolution as a process driven by competition and natural selection  Species were mutable, not fixed; and they evolved from other species through the mechanism of natural selection Natural Selection
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