TABLE OF CONTENTS Page INTRODUCTION ............................................... 2 DARWINIAN THEORY OF EVOLUTION .............................. 4 THE THEORY OF BIOLOGICAL EVOLUTION: CONTRIBUTING ELEMENTS ....................... 7 WALLACE'S CONTRIBUTIONS ................................... 13 HARDY-WEINBERG PRINCIPLE .................................. 15 COMPARISON: LAMARCK vs. DARWIN ........................... 16 DARWIN'S INFLUENCES ....................................... 20 METHODS OF SCIENTIFIC DEDUCTION ........................... 23 LIMITS TO DARWIN'S THEORY ................................. 25 MORPHOLOGICAL & BIOLOGICAL CONCEPTS ....................... 27 BIO-EVOLUTION: POPULATION vs. INDIVIDUALS ................ 29 MECHANISMS FOR GENETIC VARIATION .......................... 31 GENETIC VARIATION AND SPECIATION .......................... 35 DARWIN'S FINCHES .......................................... 37 SPECIATION vs. CONVERGENT EVOLUTION ....................... 39 CONCEPT OF ADAPTATION ..................................... 41 PUNCTUATED EQUILIBRIUM ....................................?43 VALUE/LIMITATIONS: THE THEORY OF BIOLOGICAL EVOLUTION .... 45 ALTERNATE EXPLANATIONS OF BEING ........................... 47 CONCLUSIONS ............................................... 48 INTRODUCTION Theories explaining biological evolution have been bandied about since the ancient Greeks, but it was not until the Enlightment of the 18th century that widespread acceptance and development of this theory emerged. In the mid 19th century english naturalist Charles Darwin - who has been called the "father of evolution" - conceived of the most comprehensive findings about organic evolution ever1. Today many of his principles still entail modern interpretation of evolution. I've assessed and interpreted the basis of Darwin's theories on evolution, incorporating a number of other factors concerning evolutionary theory in the process. Criticism of Darwin's conclusions abounds somewhat more than has been paid tribute to, however Darwin's findings marked a revolution of thought and social upheaval unprecedented in Western consciousness challenging not only the scientific community, but the prominent religious institution as well. Another revolution in science of a lesser nature was also spawned by Darwin, namely the remarkable simplicity with which his major work The Origin of the Species was written - straightforward English, anyone capable of a logical argument could follow it - also unprecedented in the scientific community (compare this to Isaac Newton's horribly complex work taking the scientific community years to interpret2). Evolutionary and revolutionary in more than one sense of each word. Every theory mentioned in the following reading, in fact falls back to Darwinism. DARWINIAN THEORY OF BIOLOGICAL EVOLUTION Modern conception of species and the idea of organic evolution had been part of Western consciousness since the mid-17th century (a la John Ray)3, but wide-range acceptance of this idea, beyond the bounds of the scientific community, did not arise until Darwin published his findings in 19584. Darwin first developed his theory of biological evolution in 1938, following his five-year circumglobal voyage in the southern tropics (as a naturalist) on the H.M.S. Beagle, and perusal of one Thomas Malthus' An Essay on the Principle of Population which proposed that environmental factors, such as famine and disease limited human population growth5. This had direct bearing on Darwin's theory of natural selection, furnishing him with an enhanced conceptualization of the "survival of the fittest" - the competition among individuals of the same species for limited resources - the "missing piece" to his puzzle6. For fear of contradicting his father's beliefs, Darwin did not publish his findings until he was virtually forced after Alfred Wallace sent him a short paper almost identical to his own extensive works on the theory of evolution. The two men presented a joint paper to the Linnaean Society in 1958 - Darwin published a much larger work ("a mere abstract of my material") Origin of the Species a year later, a source of undue controversy and opposition (from pious Christians)7, but remarkable development for evolutionary theory. Their findings basically stated that populations of organisms and individuals of a species were varied: some individuals were more capable of obtaining mates, food and other means of sustenance, consequently producing more offspring than less capable individuals. Their offspring would retain some of these characteristics, hence a disproportionate representation of successive individuals in future generations. Therefore future generations would tend have those characteristics of more accommodating individuals8. This is the basis of Darwin's theory of natural selection: those individuals incapable of adapting to change are eliminated in future generations, "selected against". Darwin observed that animals tended to produce more offspring than were necessary to replace themselves, leading to the logical conclusion that eventually the earth would no longer be able to support an expanding population. As a result of increasing population however, war, famine and pestilence also increase proportionately, generally maintaining comparatively stable population9. Twelve