ANTB14- LECTURE 1
Charles Darwin, who is credited with the “discovery” of the principal of natural selection in 1838, was
born in England in 1809. He died in 1882. Darwin was part of an expedition to map the coast of South
America between 1831 and 1834-35 aboard the HMS Beagle. As the Naturalist for the expedition, Darwin
was in charge of collecting and describing plant and animal specimens encountered on this expedition.
During his long journey, after observing incredible plant and animal diversity, as well as fossils, he
became interested in the question of how species come about. He was convinced that species came about
by slow change. Just HOW species changed was still a mystery. In 1838, shortly after returning home from
his journey, Darwin read Thomas Malthus’ essay titled “An Essay on the Principal of Population”. In this
essay Malthus, among other things, presents the notion that populations can increase in size exponentially
while food supplies remain relatively stable. This means that eventually a population will increase to the
point that there is not enough food or resources. This notion would become the cornerstone of Darwin’s
theory of evolution.
1. The ability of a population to expand is infinite, but the environment's ability to sustain that population
2. Organisms within the population vary, and this variation affects the ability of individuals to survive and
3. This variation is transmitted from parents to offspring.
Darwin’s theory is based on three postulates or concepts. The book summarizes these as:
1) A struggle for existence
2) Variation in fitness
3) Inheritance of variation
When resources are in demand (i.e. when the environment can’t support the existing population), a
struggle for existence occurs within the population.
Some individuals will possess physical or behavioral traits that allow them to better compete for resources
allowing those individuals to survive and reproduce.
These individuals pass these traits along to their offspring. Traits that are advantageous within the
environment are therefore retained within the population, while disadvantageous traits eventually
This process is termed NATURAL SELECTION. These advantageous traits are termed
Example: The Finches of Daphne Major (Galapagos Islands)
Studied by two Princeton biologists.