Unit 3: Evolution
Lesson 2: The Evolution of an Idea
Dating back to at least Aristotle, most Europeans accepted the idea that all living things had been
created in their present form and were immutable, meaning they were unable to change and hand not
changed. Since that time, many scientists and philosophers started questioning the idea of living things
being immutable and through careful observations, proposed ideas that contributed
to our current theory of evolution.
Comte (Count) Georges-Louis Leclerc de Buffon (1707-1788): wondered why
anatomical features that seemed to serve no purpose existed. Ex: Why do pigs (and
many other mammals) have toes that do not reach the ground? He considered this to
be strong evidence to suggest that species had changed over time. Carl Linnaeus (1707-1778) and
Erasmus Darwin (1731-1802) {Charles Darwin’s grandfather} also suggested that life changed over time.
Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1744-1829): was one of the first
scientists to propose a possible mechanism for the evolution of species. Unfortunately, some of his ideas
are now known to be flawed, but they set the stage for future scientists.
Lamarack’s First Principle: Use and disuse
He believed that structures an individual used became larger and stronger, while structures that
were not used became smaller and weaker. Ex: athletes gain muscles; astronauts experience
atrophy
Lamarack’s Second Principle: The inheritance of Acquired Characteristics
He believed that individuals could pass on to their offspring characteristics they had acquired
during their lives. Ex: if an adult giraffe stretched its neck during its lifetime, then its offspring
would be born with slightly longer necks.
Despite the flaws in his theory, he did make a number of significant contributions to our understanding
of evolution. Lamarch proposed the following;
 All species evolve over time
 A species evolves in response to its environment and becomes better adapted to that environment
 Changes are passed on from generation to generation
Georges Cuvier (1769-1832): a famous paleontologist who conducted the first detailed studies of
fossils. He noted the following:
 Fossils of very simple organisms are found in all depths of fossil deposits
 Fossils of more complex organisms are found only at shallower depths, in younger rock
 Fossils in the shallower depths are more likely to resemble living species
 Rock layers contain fossils of many species that do not occur in layers above or below them.
From his findings, Cuvier proposed the theory of catastrophism which states that the patterns of
fossils could be accounted for by a series of global catastrophes (such as floods) that wiped out most
species on Earth. These wiped out species were then replaced with a newly created set of species.
Charles Lyell (1797-1875): considered to be the father of geology. He studied rocks and fossils and
came up with the opposite conclusion to Cuvier. He proposed the theory of uniformitarianism.
 Earth has been changed by the same processes in the past that are occurring in the present
 Geological change is slow and gradual rather than fast and catastrophic
 Natural laws that influence these changes are constant and eternal, and they operated in the past
with the same intensity as they do today.
Lyell’s theories directly challenged the belief in a very young Earth. If he was right, Earth was
extremely old and life had had a very long time to undergo evolutionary change.
Charles Darwin (1809-1882): When Darwin was only 22 years old, he set sail along the HMS Beagle for
a five year voyage. During his travels, he visited the Galapagos Islands where he made a valuable
observation. He noted that the flora and fauna on the Galapagos Islands resembled to the ones on
continental South America even though they had complete different habitats. He also noted that there
were no amphibians or large mammals on the island, indicating that only species that could arrive by air
or water lived in the Galapagos. It seemed that the islands had been populated by species that arrived
from elsewhere; however, most of these species only resembled species in the mainland. This was the
beginning of the theory of evolution.
Solutions: