Scientists had four large problems to overcome before they could propose a complete evolutionary theory.  First, there was a major dispute concerning the age of the earth.  James Usher, an Irish archbishop, used evidence from the Bible to calculate that God had created the Earth in 4004 B.C.  Due to the power of the church, Usher’s estimation became an unchallenged “fact.”  Yet, some scientists began to suspect otherwise.  The process of evolution suggests that the Earth is millions of years old, conflicting with Usher's estimation.  Luckily for Darwin, geological observations arose that indicated that the earth must be much older than Usher’s calculation.  Another problem scientists faced was the widely accepted fact that species were fixed, implying that organisms could not change their forms over time.  Nearly everyone accepted the notion that species could not change due to the biblical account of creation.  However, similar to the geological observations that caused scientists to question the age of the earth, fossil records began to raise doubts about the fixity of species.  A third major factor affecting the progress of scientific discovery and advancement encompasses the previously mentioned setbacks.  Many scientists did not question the Bible due to the fear of punishment and persecution from the church.  The church also had amazing influence and censorship powers among scientific societies.  Thus, the majority of scientists were limited to practicing biblical-based research.  The final constraint to scientific headway was the rampant confusion naturalists had with living organisms.  Not only was the knowledge of living organisms lacking and imprecise, there were no standard systems of classification in existence.  Therefore, a scientist such as Darwin needed help before he continued his work on evolution.

            Six men helped pave the way for Darwin’s theory of evolution.  Carolus Linnaeus created an orderly system for organizing and naming organisms.  Linnaeus’ system, known as the Linnaean binomial system of nomenclature, is still in use today.  Linnaeus solved much of the confusion among naturalists.  Due to Linnaeus’ work, scientists had a uniform system by which they could classify the organisms they were collecting and studying.  Georges Louis Leclerc, Comte De Buffon perceived that species were not fixed.  Buffon compiled evidence from his observations of animal breeders and fruit growers suggesting that positive traits could be preserved in a species and negative traits could be weeded out.  Buffon also openly questioned the age of the earth.  He calculated that the earth began to support life at least seventy thousand years ago, implying that the Earth was much older than Usher's estimation.  Buffon’s calculation opened the doors for scientists to look at the world in a whole new light.  Additionally, Buffon recognized that life multiplied faster than food, creating a struggle for survival.  Buffon's observation would later direct Darwin toward his idea of "survival of the fittest" and natural selection. 

James Hutton rejected the biblical idea of catastrophism, which suggests that the earth has not changed since the terrible floods, volcanoes, and other calamities God used to scar the world after man’s rejection from Eden.  Instead, Hutton proposed the principle of uniformitarianism, which suggests that the geological processes taking place on the earth’s surface now are uniform to the processes that have taken place in the past. 

Jean Baptiste Lamarck put one of the first theories of evolution forward.  He called it “the theory of inheritance of acquired characteristics."  Lamarck’s theory stated that species had to adapt to changes in their environment.  Also, the offspring of those species would posses acquired traits from the previous generation. 

Thomas Malthus instilled in Darwin the ideas that “life is a struggle” and “only the fit survive."  Malthus’ Essay on the Principles of Population greatly influenced Darwin.  The essay stated that population increase would always outpace food production. 

Charles Lyell also had a profound influence on Darwin.  Darwin read Lyell’s Principles of Geology while onboard the Beagle.  Lyell’s uniformitarianist views of geology helped Darwin to realize that species must adapt and change in order to survive in a changing environment.  Lyell, along with the previously-mentioned men, helped Darwin reach his theory of evolution as the force which directed life.