The Development of Evolutionary Theory

The Development of Evolutionary Theory

Anthropology 1: Fall 2016

 Religion and science concern different aspects of the human experience, and they are not inherently mutually exclusive categories.

 Belief in God does not exclude the possibility of biological evolution; acknowledgement of evolutionary processes doesn’t preclude the existence of God.

 Evolutionary theories are not rejected by all religions or by most forms of Christianity.

 A substantial majority of Americans (about 7 in 10) believe the scientific Theory of Evolution is compatible with a belief in God – one does not preclude the other. ◦ “Evolution and Creationism in Public Education” People For the American Way Foundation

 Evolution is the most fundamental of all biological processes, but one of the most misunderstood.

 Humans evolved from a species that lived some 6-8 million years ago (mya), not monkeys or chimpanzees.

 Humans do share a recent common ancestor with other primates

 Evolution takes time; hence, the appearance of a new species is rarely witnessed

 The theory has been tested and subjected to verification through accumulated evidence (and has not been disproved)

 The theory of evolution has been supported by a mounting body of genetic evidence.

 The theory has stood the test of time.

 The theory continues to grow.

 Evolutionary principles were developed in western Europe, made possible by scientific thinking dating to the 16th century.

 Western science, however, borrowed ideas from Arab, Indian, and Chinese cultures where notions of biological evolution had already developed.

 By the 19th century, evolution wasn’t a new concept, but Natural Selection was a new theory

 The notion that species, once created, can never change

 An idea diametrically opposed to theories of biological evolution.

 To challenge the idea was to challenge the Argument from Design (life engineered by a purposeful God).

 Came with the discovery of the New World, introducing new ideas and challenging fundamental views about the planet.

 Exposure to new plants and animals increased awareness of biological diversity.

 Brave new thinkers began to challenge long held church doctrine and belief

◦ Aristotle taught that the sun and planets existed in a series of concentric spheres that revolved around the sun.

◦ Copernicus challenged the idea that the earth was the center of the universe.

◦ Galileo’s work supported the idea that the universe was a place of motion.

 John Ray, developed the concept of species.

 Groups of plants and animals could be differentiated from other groups by their ability to mate with one another and produce offspring.

 He placed such groups of reproductively isolated organisms into a single category, which he called the species.

 Carolus Linnaeus, a Swedish naturalist who developed a method of classifying plants and animals.

 In Systema Naturae, first published in 1735, he standardized Ray’s use of genus and species terminology and established the system of binomial nomenclature.

 He added two more categories: class and order.

 Linnaeus’ four-level system became the basis for taxonomy.

 Erasmus Darwin, Charles Darwin’s grandfather

 Physician, poet, and leading member of an intellectual community in England

 In a poem, expressed the view that life had originated in the seas and all species descended from a common ancestor.

 Charles read his grandfather’s writings, but how much he was influenced by them is unknown.

 Jean-Baptiste Lamarck developed a theory to explain the evolutionary process, known as the Inheritance of Acquired Characteristics.

◦ An example is the giraffe: having stripped the leaves from the lower branches of a tree, the animal tries to reach leaves on upper branches.

◦ The neck becomes slightly longer.

◦ The longer neck is passed on to offspring.

 Individual changes, transmits that change to offspring

 An opponent to Lamarck, Cuvier explained the fossil record as the result of a succession of catastrophes followed by new creation events.

 The view that the earth’s geological landscape is the result of violent cataclysmic events.

 A lawyer, geologist, and, Charles Darwin’s friend and mentor.

 Before meeting Darwin in 1836, Lyell had earned acceptance in Europe’s most prestigious scientific circles, thanks to his praised Principles of Geology, published during the years 1830–1833.

 The theory that the earth’s features are the result of long-term natural processes that continue to operate in the present as they did in the past.

 Not a new idea, proposed by James Hutton, but actually explained by Lyell, this theory opposed catastrophism and contributed strongly to the concept of immense geological time.

 Inspired both Charles Darwin and Alfred Wallace in their separate discoveries of natural selection.

 Was arguing for limits of human population growth, not concerned with how species change.

 Available resources set the limits for human population growth

 This idea was extended to all organisms by Darwin and Wallace.

Thomas Malthus and Principles of Population

 Ideas were formed while serving as a naturalist on the 5-year voyage of the HMS Beagle.

 Darwin saw the importance of biological variation within a species.

 Recognized that sexual reproduction increased variation, but did not yet know why.

 The idea that in each generation more offspring are born than survive to adulthood, coupled with the notions of competition for resources and biological diversity led to the theory of evolution.

 He wrote,“ It at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed.”

 Suggested species descended from other species and new species were influenced by environmental factors.

 Presented joint paper, coauthored with Darwin, on evolution and natural selection to the Linnean Society of London

 Darwin published “On the origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life” in 1959 in a rush to the press to beat Wallace publishing on Natural Selection first. ◦ Processes of Natural Selection,

are “the key” to understanding

evolution

 Pertaining to natural selection, a measure of relative reproductive success of individuals.

 Fitness can be measured by an individual’s genetic contribution to the next generation compared to that of other individuals.

 The ability to conceive and produce healthy offspring.

 An animal that gives birth to more young passes its genes on a faster rate than one that bears few offspring.

 An important element, however, is also the number of young raised successfully to the point where they reproduce, or differential net reproductive success.

1. All species reproduce faster rate than food supplies can increase.

2. There is biological variation within all species.

3. In each generation more individuals are produced than can survive, and because of limited resources, there is competition among individuals.

4. Individuals possessing favorable variations or traits (i.e. speed, resistance to disease, protective coloration) have an advantage over those who do not.

 They have greater fitness because their traits increase the likelihood they will survive and reproduce.

5. The environment will determine if a trait is beneficial.

◦ Geographical isolation (distance, natural barriers such as oceans) contributes to the formation of new species as individuals begin to adapt to different environments.

◦ Selective pressures (differential ecological circumstances) cause distinct species to develop. The 13 species of Galápagos finches presumably all descended from a common South American ancestor.

.

Natural Selection cont.

6. Traits are inherited and passed on to the next generation. Individuals who produce more offspring are said to have a greater reproductive success, or fitness.

7. Variations accumulate over long periods of time, so later generations may be distinct from ancestral ones.

8. As populations respond to pressures over time, they may become distinct species, descended from a common ancestor.

1. A trait must be inherited if natural selection is to act on it.

2. Natural selection can’t occur without population variation in inherited characteristics.

3. Fitness is a relative measure that changes as the environment changes.

4. Natural selection can only act on traits that affect reproduction.

 Our aggressive methods to fight microbes will lead to modified micro-organisms that have evolved to resist therapies such as antibiotics.  Use of antibiotics to treat bacterial infections weed

out vulnerable microbes, but leave less vulnerable to reproduce. Less vulnerable cause more serious forms of disease than the organisms that were eliminated.

Example: HINI Flu viruses are the result of viruses “evolving” or changing in form.

 Medical researchers try to predict which of several strains will pose the most serious threat and try to develop a vaccine that targets that specific “evolving” strain.

 If future physicians and researchers don’t understand evolution, there is little hope they can forestall potential medical crises as the pace of change in pathogens exceeds that of the antibiotics designed to defeat them.

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