Genetic drift refers to random changes in the genetic composition of a population.
It is one of the evolutionary forces that cause biological evolution, the others being selection,
mutation, and migration, or gene flow.
Modes of evolution have been proposed by several notable biologists ever since Charles Darwin proposed his theory of evolutionary descent by natural selection.
In his classic volume On the Origin of Species (1859), Darwin famously and eloquently stressed the gradual nature of descent, writing:
It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
The different modes that drives evolution includes: Mutations, genetic drift and gene flow. Gene mutations occur in two ways: they can be inherited from a parent or acquired during a person's lifetime. Gene flow (also known as gene migration) is the transfer of alleles or genes from one population to another. Genetic drift – along with natural selection, mutation, and migration is one of the basic mechanisms of evolution. In each generation, some individuals may, just by chance, leave behind a few more descendents than other individuals. The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals.