Introduction to Evolution
How do you think so many different types of organisms exist on the Earth today? –
Has the Earth always been the way is it now? If it has changed, what proof do we have?
How could it have changed?
What does evolution mean? Is it something that has occurred in the past and is it occurring today? Any proof of either case?
Evolution
§ Is defined as the process in which significant changes in the inheritable traits (genetic makeup) of a species occur over time
§ All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today
History of Evolutionary thought (Organic Evolution)
A) Spontaneous generation is what the Ancient Greeks thought occurred
B) Genesis (Bible story) 6 days of creation , Adam then Eve, All types of species formed during genesis and has remained unchanged since then. Chain of Being
Earth was formed in 4004 BC ( 6000 years old)
C) Jean Baptiste De Lamarck ( 1744 – 1829)
a. First logical argument that organisms have changed over time because of 2 evolutionary forces
i. ‘tendency to progress’ Everything starts off as a small, simple organism and through desire to become better, they change into higher forms
ii. Desire to fit into their surroundings
b. Inheritance of acquired characteristics
i. As organs and parts are used more, they become more developed. This characteristic is then passed on to their offspring.
ii. If an part is not used, it becomes small- snakes crawl through brush
Giraffe has long neck because it stretched and “subtle fluids” flowed into it developing into a longer, more developed organ. This was then passed on the offspring who stretched more etc, etc.
Problem:
Not widely accepted because everyone thought the earth was not old enough. : If you cut off mouse’s tail for many generations, the offspring still will grow a normal tail
D) Thomas Malthus (1766-1834)
Wrote in 1798 An Essay on the Principle of Population which stated that all living things tend to grow in population faster than the food supply will allow so the actual numbers remain stable. There are more offspring born then could ever survive.
E) Charles Lyell (1797-1875)
Important geologist who wrote Principles of Geology which included the idea of Uniformitarianism which states that the forces that are affecting the Earth in the present also affected the Earth in the past. This meant that the planet was much, much older than what most people thought
F) Charles Darwin (1809-1882)
Most important evolutionary scientist. He wrote a book in 1859 called On the Origin of Species which explains how organisms evolve by way of Natural Selection.
From 1831 to 1836, Darwin went on an around the world voyage of exploration aboard the HMS Beagle acting as the ship’s Naturalist. The ship visited islands in the Atlantic Ocean, the coast of South America, the Pacific Ocean, New Zealand, Australia, and the Indian Ocean. Darwin went ashore whenever he could and collected large numbers of animals, plants, insects and fossils which he sent back to England on passing vessels. He also kept very detailed journals of his discoveries. Darwin had a copy of Lyell’s book and his observations of geology confirmed Lyell’s theory that the Earth was very old. When he returned to England, he worked on many biological concepts including coral reefs, beetles, worms, and plants. When he read Malthus’ essay in 1838, the idea of Evolution by Natural Selection (survival of the fittest) popped into his head. Because it was so controversial, he wanted to wait and collect more evidence before publishing his idea. In 1858, a British naturalist named Alfred Wallace (1823-1913) wrote to Darwin for advice on a short article he had written. It was on the idea of Natural Selection….the same one Darwin had been working on for 20 years! Darwin and Wallace presented the idea together in London and in 1859 Darwin published his master piece book On the Origin of Species . It was a shock to many people that he suggested that man was related to apes. Most scientists at the time realized that it was a break through discovery in biology and quickly spread the idea to other fields. Many other people were very opposed to the theory because it contradicted the teachings of the Church. This resulted in heated debates between some of the brightest mind in England and around the world. Darwin spent most of his time at his country estate called “Downe House” where he quietly wrote more about evolution and about his other research. He had always be a shy man and did not want go into the public. He also had many problems with his health, probably from some tropical diseases he caught.