Introduction+to+Darwin's+Thinking

INTRODUCTION TO EVOLUTION When observing the world, people have noticed that organisms are well suited to their environment. Birds or moths can be well camouflaged and difficult to detect. In these cases, distinctly different colouration, such as an albino grouse on the forest floor, could lead to an early death. This is natural selection.

People also know that organisms, like corn or dogs, have many different traits. Through artificial selection, people can choose breeding patterns between dogs (or corn) to enhance particular traits. Bulldogs today have very flat faces because breeders have selected dogs with flat faces as parents.

__ How does this relate to life on the planet? __ Understanding evolution helps us look at the history of life on the planet and find relationships among organisms. This point of view is relatively recent. People have had different ways to look at the history of life on Earth.

Fossils had been found and collected for centuries. Many people saw this as evidence that catastrophes had wiped out species at different times in the past. Georges Cuvier explained the fossil evidence of changing species over time as the result of intermittent catastrophes, like floods and other, that punctuated long periods of stability where living things flourished.

In contrast, James Hutton, a Scottish geologist proposed that geological change was the result of uniform change over long periods of time. Charles Lyell popularized this point of view in a book called //Principles of Geology//. Uniformitarianism proposes that the processes of change today are similar to those of the past.

__ How do organisms change over time? __ Jean-Baptiste Lamarck explained change by the accumulation of acquired characteristics. In this example, giraffes stretch their necks to make longer necks in the next generation. 

Find more information at @http://evolution.berkeley.edu/evolibrary/article/_0/history_09



In contrast to Lamarck, Darwin explained long necks differently. The original population had giraffes with necks of various sizes. If the food sources were high, those with longer necks could reach it, survive and reproduce. Those unable to reach high then had less food to eat and did not survive or reproduce. The variation in the population decreased and eventually only giraffes with long necks survived. Such an animal would be expected in a dry environment with food sources high above the ground, like trees on the savannah of Africa.

The outstanding illustration for evolutionary change, though, is Darwin’s finch collection from the Galapagos Islands. This archipelago of volcanic islands near the equator has a vast diversity of finches but does not have some of the more common birds, like warblers or parrots. The islands are near each other, but do not share finch species.