Beginnings of Evolutionary thought Pre- Darwin

Four Problems with Creation 1 – fossils 2 – age of earth 3.- homology – anatomical studies. 4 - zoogeography

Nils Stensen, (Steno) The rocks themselves formed from fluids laying down sediment with the fossils enclosed. He could see that larger particles are at the bottom. He could even tell if it was salt or fresh water. Most important, rocks are deposited flat, layer by layer, the bottom layer being first. This is the first presentation of the theory of superposition of strata, so important to geology and this course. The theory of superposition is that when one stratum was forming, the one above it had not yet formed. There was a time sequence involved.

What are Fossils?? In 300 B.C.,Theophrastus, a student of Aristotle attributed bones in rocks to ‘plastic virtue’, a characteristic of the rocks that caused the bones to grow within them. The rocks almost have a predisposition to turn into life. Steno did not accept this explanation for the tonguestones. He made the observation, based on careful measurements, that they were shark teeth. His problem was to explain how they got into the rock. He concludes that the matrix (stuff surrounding the tooth) was not hard when the tooth was incorporated. There was no deformation around the tooth, as would occur if it grew after the rock had solidified. At one time, either the water was higher or the land was lower. (major modification of thinking). Note: Abiogenesis vs Biogenesis

Georges Cuvier August 23, 1769 – May 13, 1832 “Cuvier's scientific achievements are difficult to overestimate. It was widely recounted that he could reconstruct a skeleton based on a single bone. His work is considered the foundation of vertebrate palaeontology.”

Nearly complete skeleton of Paleotherium minus from the Paris Basin after Cuvier, 1825 Recognition of fossils as life pre-human.

William Smith, Father of historical geology

canal

Smith’s ideas 1.You can map strata by fossils 2. kind of fossils varies with age Pleistocene = 90% living forms Miocene = 60 % living forms Eocene (dawn of life) only 10% living forms 3. superposition. Pleistocene on top, Eocene on bottom.

If you look at the strata, you occasionally see an uncomformity. What is its cause and what does it represent?

Catastrophism is the doctrine proposed by the remarkable French zoologist and comparative paleontologist, Georges Cuvier ( ), that major changes in the earth's crust result from geologic catastrophes, such as eruptions of “supervolcanoes”*, rather than by slow evolutionary processes, such as alluvial depositions and small volcanic eruptions Cuvier’s study of fossils in rock strata in the environs of Paris led to one of his greatest discoveries: species become extinct. This idea was understandably hard to swallow for many people in the 19 th and 20 th centuries and even today because of its corollary that humans might one day become extinct. Even though Cuvier detested “theories” and strongly advocated “facts”, he expertly laid out his own theory on species extinction in his very readable “Discourse on the Revolutionary Upheavals on the Surface of the Globe and on the Changes which They Have Produced in the Animal Kingdom” published in 1825**.

Cuvier's example of an unconformity and faunal succession

Charles Lyell James Hutton The ideas behind uniformitarianism originated with the work of Scottish geologist James Hutton. In 1785, Hutton presented at the meetings of the Royal Society of Edinburgh that the Earth had a long history and that this history could be interpreted in terms of processes currently observed. For example, he suggested that deep soil profiles were formed by the weathering of bedrock over thousands of years. He also suggested that supernatural theories were not needed to explain the geologic history of the Earth.James Hutton

So – unconformities = major events – the flood of noah for instance. Or – simply periods of non- deposition Proof of uniformitarianism – find missing sediments elsewhere on earth. Note: both theories are extremes. We have had catastrophic events (meteors etc.) – but not universal. Also – for slow changes to occur, need a lot of time.

Comte de Buffon Homology vs analogy = relationships of structure

Homology

Mt Ararat

Early Evolutionary theories

Jean-Baptiste Lamarck ( ) Lamarck believed that giraffes stretched their necks to reach food. Their offspring and later generations inherited the resulting long necks. [[ Inheritance of acquired characteristics

Lamarck expressed the idea that by simply using or not using certain organs they may be developed or atrophied and their offspring can then inherit these acquired characteristics. (Milner p. 375, 1993) It should be noted that this theory was not widely accepted largely due to the fact that the French word that Lamarck used in the sense of “must” was translated as “wants to,” which makes it sound as though the organism decides to change its body. Furthermore, Lamarck provided no mechanism by which this could take place. ( Darwin was the one to give a mechanism for Lamarck’s idea. This mechanism is known as pangenesis. In the late 1860s Francis Galton, the cousin of Charles Darwin, Galton went further into Darwin’s theory of Pangenesis hypothesizing “that combination of gemmules might be conveyed by the blood to growing parts of the body, or passed to other bodies by reproductive organs, thereby passing on characteristics.” In order to test his hypothesis Galton gave blood transfusions between rabbits to see “whether changes of blood accelerated the appearance of inherited characteristics in offspring.” However, he could not conclude that the transfusion altered successive generations