4.1: The Modern Synthesis

Updating the Modern Synthesis: Tying it All Together

Chapter 2 examined the roles played by many different scientists, and their many careful scientific experiments, in providing the full picture of evolution. The term Modern Synthesis describes the integration of these various lines of evidence into a unified theory of evolution.

While the biggest leap forward in understanding how evolution works came with the joining (synthesis) of Darwin’s concept of natural selection with Mendel’s insights about particulate inheritance (described in detail in Chapter 3), there were some other big contributions that were crucial to making sense of the variation that was being observed. Mathematical models for evolutionary change provided the tools to study variation and became the basis for the study of population genetics (Fisher 1919; Haldane 1924). Other experiments revealed the existence of chromosomes as carriers of collections of genes (Dobzhansky 1937; Wright 1932).

Studies on wild butterflies confirmed the mathematical predictions and also led to the definition of the concept of polymorphisms to describe multiple forms of a trait (Ford 1949). These studies led to many useful advances such as the discovery that human blood type polymorphisms are maintained in the human population because they are involved in disease resistance (Ford 1942; see also the Special Topic box on Sickle Cell Anemia below).