Charles Darwin began his famous voyage on December 27^th, 1831 when he boarded the H.M.S. Beagle as an unpaid naturalist.  The ship took five years to travel around the world. At each landfall Darwin ventured ashore and collected a large amount of specimens.  Due to the great amount of specimens Darwin collected, many of Darwin’s collections were sent back to England with other ships.  Henslow stored the collections until Darwin returned.  While on the voyage, Darwin would often take long, overland excursions by himself.  One of his solo journeys lasted for a few months!  Darwin observed incredible variation and diversity among the plants and animals of the places he visited.  The Galapagos Islands had especially diverse plant and animal life.  Darwin realized that there were differences in species from different islands.  He became particularly interested in the finches.  They all appeared very similar except for variations in the beak structures, apparently for different types of food.  Another animal that caught Darwin’s attention was the Galapagos tortoise.  Darwin met a man who could tell which island the giant tortoise came from just by looking at its shell.  Darwin was puzzled as to why each island was home to a different kind of tortoise.  However, Darwin did not seriously reflect on an evolutionary theory until he returned to England and re-examined his specimens.  Instead, Darwin spent his time on the voyage observing plants, animals, and geology.

Darwin returned from his five-year voyage to find that his observations and collections had made him famous in the scientific community.   Darwin began studying and reflecting upon the specimens from his travels.  He noticed similarities between species located in the same areas.  Therefore, Darwin strongly suspected that different species had evolved from a common ancestor.  However, he still could not identify a mechanism that would cause the process of evolution to occur.  A year after returning home, Darwin read Malthus’ Essay on the Principles of Population.  Malthus stated that human population is controlled by famine, war, and disease.  Darwin extended Malthus’ idea to animals.  He believed that nature created a vast oversupply of "experiments" and then eliminates the failures by murdering them.  He asked himself which individuals survived and had offspring.  Obviously, the variations in those individuals were better adaptations to the environment.  Adaptation and random variation were methods of survival.  Therefore, Darwin realized that natural selection was the mechanism guiding evolution.  Darwin’s theory was born.  However, Erasmus Darwin, Diderot, and Lamarck had all considered the possibility of evolution from a common ancestor.  Darwin needed his idea of the mechanism of natural selection to claim originality to his theory of evolution.  Darwin’s theory was fairly simple and easy to understand, which made his book Origin of Species a popular success.  The Origin of Species clearly presented Darwin’s theory with the support of all the evidence he had accumulated.  Darwin published his book in 1859, yet, his theory was basically complete in 1839.  By 1844 Darwin had written a very accurate and well supported essay about his theory.  Why did Darwin wait another fifteen years before publishing his ideas?  Fear of controversy and persecution from the church is one possible setback.  Yet, the major deterrent was Darwin’s caution and uncertainty of his own theory.  His education had taught him that a theory must be induced from observable facts to be credible.  Yet, Darwin knew that evolution could not be observed directly and had to be deduced from indirect evidence.  Nevertheless, Darwin would soon be forced into a hasty publishing process.  In 1858 Darwin received a manuscript from Alfred Russel Wallace that clearly depicted an evolutionary theory guided by the mechanism of natural selection.  Darwin was astounded at the similarities between Wallace’s theory and his own.  Darwin published Wallace’s paper along with one of his own in a scientific journal.  The next year, Darwin finally published his masterpiece.  Although Darwin personally believed humans had evolved along with all the other species, his book did not extend the principle of evolution to man.  Darwin led a sickly life for many years until he finally died on April 19th, 1882.