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Chapter 1

Evolutionary PSYC - Chapter 1.docx

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York University
PSYC 3420
Irwin Silverman

Chapter 1: The scientific movements leading to evolutionary psychology Landmarks in the history of evolutionary thinking - Evolution refers to change over time - Lamarck was one of the first scientists to use the work biologie, thus recognizing the study of life as a distinct science - He believed in two major causes of species change: first, a natural tendency for each species to progress toward a higher form and, scond, the inheritance of acquired characteristics - Cuvier proposed a theory called catastrophism, according to which species are extinguished periodically by sudden catastrophes, such as meteorites, and then replaced by different species - Darwin’s answer to all these puzzles of life was the theory of natural selection (survival selection) and its three essential ingredients: variation, inheritance, and selection - Variations is essential for the process of evolution to operate, it provides the raw materials for evolution. Variations are inherited, passed down reliably from parents to their offspring and down to the generations - Selection, organisms with some heritable variants leave more offspring because those attributes help with the tasks of survival or reproduction - Sexual selection focused on the adaption’s that have arisen as a consequence of successful mating - Two primary means by which sexual selection could operate are; - 1. Intrasexual competition, competition between members of one sex, the outcomes of which contributed to mating access to the other sex. Qualities lead to success in the same sex contests, such as greater size, strength, or athletic ability, will be passed on to the next generation by virtue of mating success of the victors - 2. Intersexual selection, evolutionary changes occurs simply because the qualities that are desired in a mate increase in frequency with the passing of each generation. Darwin called this female choice because females of many species we discriminating or choosy about whom they mated with - Genetic drift, which is defined as random changes in the genetic makeup of a population - Random changes come about through several processes, including mutation (a random heredity change in DNA), founder effects, and genetic bottlenecks - Founder effect occurs when a small portion of a population establishes a new colony and the founders of the new colony are not entirely genetically representative of the original population - Genetic bottlenecks, which happen when a population shrinks, perhaps owing to a random catastrophe such as an earthquake - Evolution by natural selection is not forward-looking and it not intentional - Another critical feature of selection is that it is gradual - One objection was that Darwinian evolution lacked a coherent theory of inheritance. Darwin himself preferred a blending theory of inheritance, in which offspring are mixtures of their parents - Another objection was that some biologists could not imagine how the early stages of the evolution of an adaption could be useful to an organism - A third objection came from religious creationists, many whom viewed species as immutable (unchanging) and created by a deity rather than by the gradual process of evolution by selection - The qualities of the parents are not blended with each other, but rather are passed on intact to their offspring in distinct packets called genes. Genes must be passed on, not acquired - Mendel’s discovery that inheritance is particulate, which he demonstrated by crossbreeding different strains of pea plants - A gene is defined as the smallest discrete unit that is inherited by offspring intact, without being broken up or blended - Genotypes refer to the entire collection of genes within an individual. They are not passed down to offspring intact - Rather in sexually reproducing species such as our own, genotypes are broken up with each generation, thus each of us inherits a random half of genes from our mother’s genotype and a random half from our father’s genotype - Darwin clearly envisioned his theory of natural selection as being just as applicable to behaviour, including social behaviour, as to physical structures. First, all behaviour requires physical structures. Second, species can be bred for certain behavioural characteristics using the principle of selection - Ethology is the study of the proximate mechanisms and adaptive value of animal behaviour. Lorenz, imprinting in birds was a vivid phenomenon used to launch this new field - Ethologists were interested in four key issues, which have become known as the four why’s of behaviour: 1. The immediate influences on behaviour 2. The developmental influences 3. The function or the adaptive purpose it fulfills 4. The evolutionary or phylogentic origins - Hamilton proposed a radical new revision of evolutionary theory, which he termed inclusive fitness theory - Hamilton reasoned that classical fitness, the measure of an individual’s direct reproductive success in passing on genes through the production of offspring was too narrow to describe the process of evolution by selection - He theorized that natural selection favors characteristics that cause an organism’s genes to be passed on, regardless of whether the organism produces offspring directly - Parental care, investing in one’s own children was reinterpreted as merely a special case of caring for kin who carry copies of parent’s genes in the bodies - An organism can also increase the reproduction of its genes by helping brothers, sisters, nieces or nephews to survive and reproduce
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