Charles Darwin and Biological Evolution Part I - Creation to Evolution Charles Darwin and Evolution The modern theory of evolution was first developed by Charles Robert Darwin (1809-1882). • But Darwin began his adult life an avowed Creationist who was studying for the Anglican clergy! The logic of (Paley’s ‘Evidences of Christianity’) and, as I may add, of his 'Natural Theology,' gave me as much delight as did Euclid. What happened? Dr. Robert Darwin Charles Robert Darwin • Born February 12th, 1809 • The Mount, Shrewsbury, England • Son of a gentleman physician in a wealthy family. • Did not show any strong aptitudes as a child. • His father decided Charles would study medicine. • Attended University of Edinburgh for medical school. • Charles did not enjoy the heavy emphasis on lectures at Edinburgh. • He was very put off by the two surgical operations he observed. • After two years he left Edinburgh. “Dr. Munro made his lectures on human anatomy as dull, as he was himself, and the subject disgusted me.” • Enrolled at Cambridge to prepare for a career as an Anglican clergyman. • Studied classics and theology, but spent most of his time hanging out with zoologists, botanists, and geologists, developing a keen interest in natural history. • Darwin began cultivating an active interest in botany and geology at Cambridge. • He joined a geology professor, the Reverend Adam Sedgwick, on a two-week expedition mapping the rock strata of Wales (part of Sedgwick’s Cambrian project. Grab your hammer and clinometer Charles - there’s work to be done! Darwin graduated Cambridge and would likely have entered the Anglican priesthood, but for an unusual offer…. The Voyage of the Beagle • Darwin is offered the role of “captain’s companion” on a survey voyage of the HMS Beagle. • Captain Fitzroy is looking for a gentleman naturalist to join the crew on a survey of the coast of South America. • 1831 - Darwin sets sail on a ‘two year’ expedition aboard the Beagle. •The Beagle spends 5 years circumnavigating South America and the Southern Hemisphere. •Darwin spends most of that time onshore - traveling, exploring, collecting, and keeping detailed notebooks and a journal. Voyage of the Beagle The Voyage of the Beagle •Darwin observes and collects animals, plants, and fossils. •He studies the geology of South America and of the islands he visits. •Carries with him Principles of Geology by Sir Charles Lyell. Geologists in the 1800s were very concerned with questions of origin: the origin of different rock types, the origin of different sedimentary formations, geologic features, etc. Based on his observations on the Beagle voyage, Darwin worked out the origin of coral atolls from volcanic islands. Fossils Darwin found in S. America led him to question the origin of species. Glyptodon ? Megatherium ? This wonderful relationship in the same continent between the dead and the living, will, I do not doubt, hereafter throw more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts. Darwin observed two similar species of ‘ostrich’ separated by the Rio Negro in Argentina. American Rhea Darwin’s Rhea He puzzled over why there should be two similar species of this bird occupying the same habitat in 11 adjacent regions. Darwin experienced a powerful earthquake while ashore in Chile. Exploring the coastline he saw areas where the sea floor had been uplifted several meters above sea level. Later, Darwin noted fossil seashells in the rock strata high up in the Chilean Andes. He surmised that the rocks in the high peaks had been uplifted from sea level over a very long time in a manner analogous to the uplift he saw from the earthquake. The power of small changes, added together over geological spans of time, would become an important theme in Darwin’s thinking. One last stop in S. America: The Galápagos Islands Pinta Marchena Genovesa (Tower) 0° Santiago Santa Cruz Fernandina Santa Fé San Cristóbal Isabela Floreana “In the morning (17th,) we landed on Chatham Island, which, like the others, rises with a tame and rounded outline, interrupted only here and there by scattered hillocks—the remains of former craters.” The small bay where Darwin first came ashore in the Galápagos on Chatham (San Cristobal) Island. Espánola Sierra Negra (Isabela) The Galapagos Islands are named for the giant tortoises that live there. Darwin was told that each island had its own variety of tortoise, although he did not make much of that at first. “My attention was first called to this fact by the Vice-Governor, Mr. Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought.” This one is shaped like a burrito! Geochelone elephantophus hoodensis Marine iguanas - unique to the Galapagos Islands Galapagos land iguana - lives on the same islands as the marine iguana, but feeds on cactus instead of seaweed. The Galapagos penguin the only penguin that lives near the equator! The flightless cormorant almost identical to its mainland cousins except for the stubby, useless wings! Opuntia cactus - we have them growing on the Hofstra campus, but not as trees! Darwin collected many types of birds from the Galapagos, including a number of species that all turned out to be types of finches. Daphne Major “The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body, and plumage: there are thirteen species, which Mr. Gould has divided into four sub-groups.” Woodpecker finch Large ground finch Mangrove finch Medium ground finch You mean Darwin’s finches! Seed Eaters Small ground finch Vegetarian finch Cactus finch Sharp billed ground finch Large cactus finch Large tree finch Medium tree finch Small tree finch Ground finches Warbler finch Tree finches Warbler-like finch Mainland finch ancestor Woodpecker finch Large ground finch Mangrove finch Medium ground finch Cactus flower eaters Small ground finch Vegetarian finch Cactus finch Sharp billed ground finch Large cactus finch Large tree finch Medium tree finch Small tree finch Ground finches Warbler finch Tree finches Warbler-like finch Mainland finch ancestor Woodpecker finch Large ground finch Mangrove finch Medium ground finch Small ground finch Vegetarian finch Cactus finch Sharp billed ground finch Large cactus finch Large tree finch Medium tree finch Small tree finch Insect eaters Ground finches Warbler finch Tree finches Warbler-like finch Mainland finch ancestor Woodpecker finch Large ground finch Mangrove finch Medium ground finch Small ground finch Vegetarian finch Cactus finch Sharp billed ground finch Large cactus finch Large tree finch Medium tree finch Small tree finch Ground finches Warbler finch Tree finches Warbler-like finch Mainland finch ancestor Vampire Finches Darwin was puzzled by what he saw on the Galápagos Islands • Absence of native mammals and frogs in the Galápagos. • Galápagos animals and plants were clearly similar to those he had seen on the South American mainland, but they were different species. • Why should these small, similar islands, mostly within sight of each other, have so many unique species of plants and animals, many peculiar to a particular island? “…it is the circumstance, that several of the islands possess their own species of the tortoise, mocking thrush, finches, and numerous plants, …that strikes me with wonder.” Darwin was also impressed with the volcanic landscapes of the Galápagos and realized that the islands were geologically very new. “Seeing every height crowned with its crater, and the boundaries of most of the lava-streams still distinct, we are led to believe that within a period, geologically recent, the unbroken ocean was here spread out.” After returning to England, Darwin was informed by an ornithologist that most of the small land birds he brought back from the Galápagos were actually different species of finch. “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.” “[In the Galapagos], both in space and time, we seem to be brought somewhat near to that great fact–that mystery of mysteries–the appearance of new beings on this earth.” Darwin does not directly question creationism in The Voyage of the Beagle, but he drops hints that show he was seriously thinking about the origin of new species when he wrote it. Within a year of returning from the Beagle voyage, Darwin began a series of investigations into the question of organic evolution that would occupy him for the rest of his life. “ From this work I became convinced that species are not immutable. It is like confessing a murder.”