British naturalist Charles Darwin is best known as the first person to accurately explain how evolution works. Around the same time that Darwin was formulating his theory of evolution, the less well-known Scottish naturalist, Alfred Russel Wallace, arrived independently at the same conclusion.
It is not a coincidence that two mid-19th century British naturalists developed the same theory around the same time. If Darwin and Wallace had not formulated their theory of evolution then another British or French naturalist would have done so soon afterward. This is because the most of the groundwork for the Darwin-Wallace theory of evolution was laid by French and British scholars in preceding decades. In a longer view, Darwin’s theory of evolution was the culmination of centuries of theories and observations.
The Fixity of Species Theory:
In medieval times the European worldview was based on the idea that the world was static. Medieval Europeans believed that life forms and their relationship to one another never changed. People believed that the world was created ‘as is’. People believed that the world and all its living things had been created in their present form and that they had never, and would never, change. This idea is known as the ‘fixity of species’.
This medieval worldview began to crumble during the 15th century. World exploration and the scientific revolution challenged old notions of a static, unchanging universe.
The scientific revolution set the stage for advances in the field of natural science. In the 17th century Cambridge University educated minister John Ray proposed the idea of dividing living things into different species and genera. A species signified a reproductively isolated group of organisms. In other words, organisms that could procreate with one another but not with other types of organisms.
Swedish naturalist Carolus Linnaeus (1707-1778) elaborated on Ray’s system to develop a standardized system for classifying all living organisms. Linnaeus’ system of classification is the basis of the modern scientific classification of living things. In his classification system, Linnaeus added two more categories, ‘order’ and ‘class’, to Ray’s ‘genus’ and ‘species’. Linnaeus’ system was controversial because it classified human beings along with other organisms. This challenged the view that humans were different from other living things. Linnaeus classified humans in the genus Homo and the species sapiens- hence the modern scientific designation of human beings, Homo sapiens.
Linnaeus, however, originally believed in the fixity of species. It was only later in life, in the face of overwhelming evidence, that he began to question this belief.
Buffon and Erasmus Darwin’s Theories of Evolution:
French naturalist Georges-Louis Leclerc de Buffon (1707-1788) recognized that organisms could be altered by their environment. He argued that when organisms migrated to a new environment they gradually acquired new characteristics to adapt to their new surroundings. Buffon, however, rejected the notion that one species could give rise to another.
Charles Darwin’s grandfather, Erasmus Darwin, was a prominent intellectual and poet. Erasmus expressed the view that life had originated in the sea and that all species were descended from a common ancestor. It is known that Charles Darwin read his grandfather’s writing but it is unclear how much Charles’ theory of evolution was influenced by his grandfather’s ideas.
Lamarck’s Theory of Evolution:
Although both Buffon and Erasmus Darwin stated a belief in evolutionary change, neither tried to explain the process of evolution. The first to try to explain how evolution worked was French naturalist Jean-Baptiste Lamarck (1744-1829). Lamarck’s theory was that traits acquired by animals during their lifetime could be passed on to their progeny.
So, for example, a giraffe eats all the leaves of the lower branches of nearby trees. In order to reach the leaves of higher branches, the giraffe strains its neck until its neck becomes slightly longer. The longer neck is then passed on to the giraffe’s offspring. Lamarck’s theory has now been discredited because it is inconsistent with what is now known of genetic inheritance. Although Lamarck’s theory has become the subject of ridicule, it is important because it recognized the role of external environmental forces on the evolutionary development of organisms.
Cuvier’s Catastrophism Theory:
One of the most vigorous critics of Lamarck’s theory was French vertebrate paleontologist Georges Cuvier (1769-1832). Cuvier rejected the concept of evolution. Cuvier realized, however, from studying fossils, that certain life forms that had once existed had become extinct. Cuvier was one of the first to introduce the concept of extinction. Cuvier attributed the disappearance of old species to catastrophic events like Noah’s Flood. He believed that catastrophic extinctions were followed by new creation events. In this way, old species were replaced by completely new, more advanced species.
Summary:
In the centuries and decades before Darwin formulated his theory of evolution, several Western European scholars came up with a variety of theories to explain the existence of organisms in their present form. In medieval times and afterward the prevailing view was in the fixity of species- that organisms had been created in their present form and that they never changed. French naturalist Buffon and Charles Darwin’s grandfather Erasmus Darwin stated a belief in evolution, but did not try to explain how evolution worked. French naturalist Jean-Baptiste Lamarck tried to explain how evolution worked, but his theories have now been discredited. French paleontologist Georges Cuvier, on the other hand, rejected the notion of evolution altogether. He used a catastrophism theory to explain the extinction of old species and their replacement by more advanced species. Although Cuvier did not believe in evolution, he helped to introduce the concept of extinction and the appearance of new species.
Reference:
‘The Development of Evolutionary Theory’, Chapter 2 in Robert Jurmain et al. Introduction to Physical Anthropology. Eleventh Edition. Belmont, California: Thomson Higher Education, 2008., p. 18- 35.
