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“This abstract, which I now publish, must necessarily be imperfect…no doubt errors have crept in, though I hope I have always been cautious in trusting to good authorities alone…A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question; and this cannot possibly be done here.” • Charles Darwin, On the Origin of Species, 1859.
Historical Development Before Darwin • 1600’s European anatomists began to look at life for themselves. • Study of the intricacies of God’s design. • Guided researchers to the fundamental question of how life works.
Geologist Frame of Mind • 1785 James Hutton proposed that the Earth must be older than a few thousand years by looking at layers formed in structures. • Looking at life history what could you conclude about living organisms and the environment? • Life evolves as environments change
Biological Evolution • How would you define this term? • Descent with modification. • Current species are descendants of ancestral species that have changed over time. • We will build on this definition in the coming days.
Historical Development The Ecology of Human Populations • 1798 Thomas Malthus authors An Essay on the Principle of Population as it affects the Future Improvement of Society. • Population growth and supply. • Popularized the idea of limiting factors.
Historical Development Early Concepts of Evolution • Late 1700s Jean Baptiste Lamarck coined the idea of acquired characteristics through use and disuse. • What is an acquired characteristic?
Lamarck • Nature drives organisms to greater complexity over time. • Although his ideas proven incorrect he was one of the most intelligent biologists of his time. • Evolutionary change explains patterns in fossils and the match of organisms to their environments.
Lamarck • Use and Disuse • Parts of the body that are used become stronger while those that are not used deteriorate. • Inheritance of acquired characteristics • Organisms can pass these modifications to their offspring.
Lamarck • Ideas make sense, let’s see if it explains what we can observe.
Early Concepts of Evolution • You lift weights your entire life and have giant arms. Your son will have giant arms.
Early Concepts of Evolution • You lose your arm in an accident. Due to this your child will not have an arm.
Early Concepts of Evolution • Giraffes stretch their necks to get food. This need to stretch their neck drives evolution and the baby giraffe will have a longer neck.
Lamarck Early Evolutionary Concepts • Tendency toward perfection and complexity. • Use and disuse. • Inheritance of acquired traits. These ideas DO NOT explain current evolutionary theory, but paved the way for its development.
Historical Development Natural Selection • 1859 Charles Darwin publishes On the Origin of Species. • Found inspiration from Thomas Malthus and Alfred Russel Wallace (you snooze, you loose). • Observable changes through selection pressure in nature. • No mechanism for how the traits are passed from parent to offspring.
Historical Development The Monk and his Peas. • 1850s GregorMendal interbred peas and kept track of their traits. • In certain traits he found specific ratios based on the way he interbred the plants. • This was the first step in the discovery of genetics.
Historical Development Birth of Genetics • Early 1900s Thomas Hunt Morgan bred fruit flies and studied mutations. • Mutations do not always create a new species as had been suggested. • Source of the variation that Darwin suggested in his original proposal!
Historical Development Driving Forces of Natural Selection • 1920’s the scientific field of genetics became popular. Mutations were critically analyzed. • Ronald Fisher, JBS Haldane, and Sewall Wright tested the idea that mutations can cause small changes in the individual that can be positive or deleterious or neither in the environment. • They were the first to create a mathematical model of evolution. • Thinking was that small changes over time change the genetic make-up of a species.
Historical Development The Modern Synthesis • 1930’s Theodosius Dobzhansky combined years of genetics and population research. • Studied fruit flies and identified that all species do not have identical genes. • Explanation for how species actually came to existence using genetics. • Set the foundations for future studies in evolution and building the modern synthesis.
Historical Development DNA • Scientists knew about genes but had no idea what molecule the genetic material actually was. • Experiments verified that nucleic acids contain hereditary material. • 1953 Francis Watson and James Crick use Rosalind Franklin’s image to create a double helix model of the structure of DNA (University of California Museum of Paleontology, 2011). • Model opened up avenues of research including DNA replication, transcription, and translation. • Darwin’s “variations” were identified as molecules nearly a century later.
Historical Development Evolution and Development • 1977 Stephen Jay Gould recognized that timing of developmental gene expression can greatly alter an organism (University of California Museum of Paleontology, 2011). • Mutations can occur in developmental genes. • Currently scientists are studying the timing of these developmental genes and mutations and how they influence genetic development of all body parts and may account for the variation of body plans found in nature.
Pattern of Historical Change • Rational beings seeking the perfection of God in the natural world. • Observations about the earth and life through anatomy. • Forces causing the diversity of animals proposed and widely accepted later to be modified. • Extrapolation of ideas about the human population with application to the natural world. • Observation of the great diversity of animals and how these differences suit them in their habitats.
Pattern of Historical Change • Experimenting with the idea of heredity to obtain measurable results. • Observation and interdisciplinary connections to earth sciences lead to publication of On the Origin of Species. • After publication a great curiosity with what the “variations” in natural selection were. • Increased technology and amounts of data built upon the foundational mechanism proposed by Darwin to the theory of evolution driven by natural selection that is accepted today.
