Evolution can be seen in action over short periods of time, such as days, weeks, and years, and it can be seen in the study of fossils over long periods of time.
The history of ideas that influenced Darwin as he made his observations is the first part of the history of evolutionary thought.
We look at the evidence that allowed Darwin to develop his theory of evolution by natural selection.
The modern evidence supports Darwin's theory.
There was a new chapter in the history of biology in December of 1831.
During his journey around the world, Darwin wanted to collect and record the geological and biological diversity he saw.
He saw a bird called the rhea, which looks like an African ostrich, along the east coast of South America.
He saw a mammal that looked like the European rabbit in the desert.
He observed fossils in the mountains.
He found a lot of life in the rain forest.
He saw marine iguanas with blunt snouts that were suited for eating algae.
The view of the fixity of species was forged from deep-seeded religious beliefs, not from observing the natural world.
Darwin's observations challenged his belief that species don't change over time, in fact, his observations of geological formations and species variation led him to propose a process by which species arise and change.
"Genetic change occurs in a species over time, which leads to their genetic and phenotypic differences."
Natural forces are to blame for this process.
The scientific and intellectual revolution that began in Europe in the late 1800s gave rise to this new view that was not readily accepted by Darwin's peers.
Since Darwin's idea of natural selection was published more than 150 years ago, it has been subjected to rigorous scientific tests so that it is now considered one of the unifying theories of biology.
The unity and diversity of life on Earth is explained by Darwin's theory of evolution by natural selection.
Many people believe that Darwin forged this change in worldview by himself, but many biologists during the preceding century and some of Darwin's peers had a large influence on him as he developed his theory.
As the natural history of new lands was being mapped and documented, this was a time of exploration and discovery.
It was a time of rapid expansion of an understanding of the Earth's biological diversity when shipments of strange plants and animals from new regions arrived in England.
Darwin's theory grew in this atmosphere of discovery.
Many of the beliefs of the eighteenth century can be traced to the works of the ancient Greek philosophers.
Plato said that every species on Earth has a perfect form and species variation is not perfect.
The organisms can be arranged based on their order of increasing complexity.
Count Buffon was a natural history author who wrote a 44volume series about all known plants and animals.
He proposed various causes, such as environmental influence and the struggle for existence.
The support of evolution seemed to waiver, and often he professed to believe in special creation and the fixity of species.
Taxonomy, the science of classifying organisms, was an important endeavor during the mid-eighteenth century.
Linnaeus believed that each species had an "ideal" form.
The evaluation of similar structures across a variety of species was used by biologists to classify organisms into groups.
The remains of plants and animals from the past were discovered by scientists by the late 18th century.
Initially, scientists believed that each type of fossil had a living descendant, but eventually some fossils did not match with known species.
Baron Cuvier was the first to suggest that some species that had been in the fossil record had become extinct.
Charles Darwin's grandfather was a physician.
Comments and footnotes in his writings suggested the possibility of evolution.
His conclusions were based on the fact that animals have lost most or all of their function in a descendant.
Darwin thought that species might evolve, but he didn't have a way to make it happen.
A system of classifying animals was developed by Baron Cuvier.
The science of paleontology was founded by him.
The study of fossils and its use of fossil bones to deduce the structure of an animal was quite skilled.
He proposed that the sudden changes in fossil variation could be explained by a series of local catastrophes and mass extinctions.
The assembly of life-forms that occupied a particular region over time was the result of these catastrophes.
Cuvier's followers believed that God had created new species to repopulate the world and that there had been worldwide catastrophes.
Jean-Baptiste de Lamarck was the first Biologist to offer a testable hypothesis that explained how evolution occurs.
Lamarck proposed that more complex organisms are descended from less complex organisms.
Increasing complexity is the result of a natural motivating force that is inherent in all living organisms.