Definition of the Modern Synthesis
The modern synthesis, also known as the neo-Darwinian synthesis, is a comprehensive theory of evolution developed in the 1930s and 1940s. It integrates Charles Darwin's concept of natural selection with Gregor Mendel's principles of genetics, along with contributions from population genetics, systematics, and paleontology. This framework explains how evolutionary change occurs through the gradual accumulation of small genetic variations in populations over time.
Key Principles and Components
Central to the modern synthesis are the mechanisms of variation and inheritance. Genetic mutations and sexual recombination provide the raw material for variation, while natural selection acts as the primary force directing adaptation. Population genetics, pioneered by figures like Ronald Fisher, J.B.S. Haldane, and Sewall Wright, quantifies how allele frequencies change in populations. Other components include genetic drift, gene flow, and the role of speciation through geographic isolation.
Practical Example: Industrial Melanism in Peppered Moths
A classic example is the peppered moth (Biston betularia) in industrial England. Light-colored moths were once dominant, blending with lichen-covered trees. During the Industrial Revolution, pollution darkened trees, favoring darker mutants. Natural selection rapidly increased the frequency of the dark allele, demonstrating how genetic variation and environmental pressures lead to evolutionary change within a single generation's timescale.
Importance and Applications
The modern synthesis revolutionized biology by providing a mechanistic basis for evolution, enabling predictions about biodiversity and adaptation. It underpins fields like conservation biology, where it informs strategies to preserve genetic diversity, and medicine, such as understanding pathogen evolution and antibiotic resistance. Despite extensions like evo-devo, it remains foundational for interpreting fossil records and molecular data.