How Did Sewall Wright Contribution to the Theory of Evolution?


Diego Sanchez

Sewall Wright was an American geneticist who made significant contributions to the field of evolutionary biology. His work on population genetics and the concept of genetic drift revolutionized our understanding of how evolution works. In this article, we will explore Sewall Wright’s contribution to the theory of evolution.

Early Life and Education

Sewall Wright was born on December 21, 1889, in Melrose, Massachusetts. He was the eldest of three brothers and showed an early interest in biology. He received his undergraduate degree from Stanford University in 1912 and went on to obtain a PhD from Harvard University in 1915.

Population Genetics

Sewall Wright is best known for his work on population genetics. He developed mathematical models that explained how genes are passed down from one generation to the next and how they change over time. He proposed that changes in gene frequencies could occur due to random events, such as mutations or genetic drift.

Wright’s theory of genetic drift suggested that small populations were more likely to experience random fluctuations in gene frequencies than large populations. This idea challenged the prevailing view that natural selection was the primary driver of evolution.

The Shifting Balance Theory

In addition to his work on population genetics, Sewall Wright also developed the shifting balance theory. This theory proposed that evolution occurs through a combination of natural selection, genetic drift, and migration.

According to the shifting balance theory, small isolated populations may evolve differently due to random events such as mutations or genetic drift. Over time, these populations may become better adapted to their environments than larger populations.

As these isolated populations come into contact with each other through migration or other means, their different adaptations may interact in unexpected ways. This interaction can lead to new evolutionary pathways and eventually result in speciation.


Sewall Wright’s contributions to the theory of evolution were significant. His work on population genetics and the concept of genetic drift challenged prevailing views on how evolution works. His shifting balance theory provided a new perspective on how isolated populations can evolve differently and eventually lead to speciation.

In summary, Sewall Wright was a pioneer in the field of evolutionary biology whose ideas continue to shape our understanding of how life evolves.