INTRODUCTION TO EVOLUTION I. History of Evolutionary Thought

There was a general consensus that the age of the earth was as old as recorded human history – most people could not imagine the vast expanses of time that existed before the presence of humans. People also did not perceive the great changes in the geology, geography and biology that occur through the accumulation of small processes over large spans of time

II. Establishing the Age of the Earth Need an ancient earth to account for the biological changes that have occurred. Use of dating rocks in the solar system not subjected to plate tectonics – meteorites, moon rocks Relative positions of fossils – time it takes for multiple layers to form

A. Fossil evidence The fact of extinction Seemingly misplaced fossils – terrestrial/marine fossils, Warm/cold fossils Multiple layers

B. Geological Observations Continental drift time Uplifting of land masses Flooding of continents Changes in ecosystems over time – desert/sea, coal beds on mountain tops, Salt Lake…

C. Radioactive Dating

D. Astronomical Determinations The time it takes for the light from some distant objects in the universe to reach us is billions of years.

E. LIFE HISTORY 1. Important dates Age of the Universe – 13 – 14 billion years Age of the Earth – 4.6 billion years First Life on Earth – 3.5 – 4 billion years First eukaryotic life – 2 billion years ago First Multicellular life – 1.2 billion years ago Cretaceous extinction – 65 million years ago First “humans” – diverged from chimpanzees and bonobos 6 million years ago First Homo sapiens – 200,000 years ago

2. Major Eras Cenozoic Mesozoic Paleozoic Proterozoic Archean