Early Ideas About Evolution

Evolution is the process of biological change by which descendants come to differ from their ancestors.

Divine creation Species are unchanged

CHARLES DARWIN father of evolution

Early scientists proposed ideas about evolution which influenced Darwin. Linnaeus (1700s) developed a classification system for all types of organisms based on similarities. Buffon (1700s) based on fossil evidence, he proposed that species shared ancestors instead of arising separately. He suggested that the Earth was much older.

Incorrect! WHY? Erasmus Darwin (1760’s) All living things were descended from a common ancestor and more complex forms arose from less complex forms. Jean-Baptist Lamarck proposed that changes in the environment caused organism’s behavior to change, leading to greater or lesser use of a structure or organ. The structure would increase in size because of use or decrease in size because of disuse. Incorrect! WHY?

Theories of geologic change set the stage for Darwin’s theory. The study of fossils by Cuvier (1800’s) led to the idea that organisms could become extinct. Different species from adjacent areas would move into the newly vacated area.

Geologist James Hutton (late 1700’s) proposed that the changes he observed in landforms resulted from small changes over a long period of time (gradualism). Charles Lyell (1830’s) Earth was ancient…millions of years old. Theory of uniformitarianism – geologic processes that shape Earth are uniform through time. These geological processes are slow but cause great change.

The observations that Darwin made on a voyage of HMS Beagle (1831-1836) led to his ideas about evolution.  

Darwin observed various adaptations of plants and animals that inhabited such diverse environments as jungles, grasslands, and deserts.

He also noted that plants and animals in South America closely resembled species there rather than species in Europe.

Darwin visited the Galapagos Islands, 500 miles off the coast of Ecuador.

Darwin was struck by the variation of traits between species of finches in the Galapagos Islands. The most striking difference among them are their beaks.

Darwin observed that finches found on the Galapagos resembled species living on the mainland. Darwin observed that finches found on one island looked different from those on nearby islands.

Their beak shapes seemed well suited to their diets. These observations led Darwin to realize that species may somehow be able to adapt to their surroundings. An adaptation is a heritable characteristic that increases an organism’s ability to survive and reproduce in its environment.

Darwin hypothesized that the Galapagos had been colonized by finches that had strayed from South America and had then diversified on the various islands.

Evolution of Life