The Theory of Evolution by Natural Selection Part 1: Background

Charles Darwin  Born: 1809 (over 200 years ago)  Father was a minister.  Studied medicine & theology at Cambridge University, England..  Preferred natural history

Charles Darwin - 2  1831 – Darwin was hired as a naturalist aboard the HMS Beagle.  5 years on the ship – a journey to chart sections of the coast of South America.  He was seasick for most of the voyage.

Source:

HMS Beagle route map (5 year voyage)

Charles Darwin - 3  Darwin’s job was to collect biological specimens of the plants and animals that lived in these places and keep records of what he found.  He did a remarkable job of it, sending back over 5,400 specimens to naturalist professors in England. Notice on some fungi collected by C. Darwin, Esq., in South America and the Islands of the Pacific. Annals and Magazine of Natural History 9: Source:

Charles Darwin - 4  Darwin became interested in the geographical distribution of organisms.  Why did species living today in the jungles and grasslands of South America look more like fossils of S. America than the jungles and grasslands of Africa? Darwin draws the first PHYLOGENIC TREE

Charles Darwin - 5  “When on board H.M.S. ‘Beagle’ as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species.…”

Alfred Russell Wallace  A contemporary and friend of Darwin’s, was coming up with the same ideas and getting ready to publish his work. He sent Darwin a copy of a paper he wrote and was going to publish.  This prompted Darwin to panic and he worked frantically for a year to publish his work earlier than he wanted to.  A paper that Darwin wrote 15 years earlier established that it was his original idea.  Wallace agreed that Darwin should be credited.

Charles Darwin - 6  1859 – On the Origin of Species by Means of Natural Selection  Proposed the idea of “Descent with Modification”. Did NOT use the term “Evolution”, used the term “transmutation” of species.  What did he mean by descent?  What is a descendant?

Source: Highest frequency words are larger Wordle of the entire text of the Origin of Species

Think. Answer the questions below  What did Darwin mean by descent?  What is a descendant?  What is an ancestor?  What did he mean by modification?  What does it mean to modify something?  What did he mean by natural selection?  What is nature?  What does it mean to select something?

Charles Darwin - 7  1859 – On the Origin of Species...After 5 years on board the Beagle, and 20 years of dedicated study, Darwin’s idea was:  All organisms on earth are related to each other through descent from some common ancestor.  Species alive today are descendants of species that came before. Darwin’s illustration of trimorphic flowers of Lythrum salicaria in Forms of Flowers, 1877

Charles Darwin - 8  Most importantly, Darwin provided a plausible explanation for how that could happen: Natural Selection On the Scelidothere (Scelidotherium leptocephalum, Owen). [Read 18 December 1856] Philosophical Transactions of the Royal Society of London 147:

 Darwin’s ideas were controversial at the time of publication, many scientists disputed his ideas, and Darwin was ridiculed in the press. Charles Darwin - 9

Charles Darwin - 10  However… His ideas have stood every scientific test put to them, new evidence gathered since Darwin’s day continues to support his idea.  You have looked at a tiny portion of this body of evidence Morphological Embryological Geological Fossils Molecular DNA amino acid sequences in common proteins, and radiometric dating.  Scientists today accept descent with modification by natural selection as a fact based on the enormous body of evidence.

Charles Darwin - 11  Why do you think Darwin waited to present his ideas to the public?  Why was he criticized?