Motoo Kimura was a prominent Japanese biologist best known for his formulation of the neutral theory of molecular evolution. His work emphasized that much of the genetic variation seen in populations is due to random genetic drift of neutral mutations, rather than being driven by natural selection. This theory has significant implications for understanding how evolutionary processes shape genetic diversity over time.
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Motoo Kimura proposed the neutral theory in the 1960s, suggesting that most evolutionary changes at the molecular level are caused by genetic drift acting on neutral mutations.
His theory challenged the traditional view that natural selection was the primary driving force behind molecular evolution.
Kimura's work has led to greater appreciation of the role of non-selective processes in shaping genetic diversity.
The neutral theory laid the groundwork for subsequent research in population genetics and molecular evolution.
Kimura also introduced concepts like the 'molecular clock', which uses neutral mutation rates to estimate the time of divergence between species.
Review Questions
How did Motoo Kimura's neutral theory challenge traditional views on molecular evolution?
Motoo Kimura's neutral theory fundamentally changed how scientists viewed molecular evolution by arguing that most genetic variations are not necessarily shaped by natural selection but rather by random genetic drift of neutral mutations. This contrasted with the traditional focus on natural selection as the primary mechanism driving evolutionary change. As a result, his theory provided a new perspective on how genetic diversity can arise and be maintained within populations over time.
Discuss the implications of Kimura's neutral theory on our understanding of genetic drift and its effects on populations.
Kimura's neutral theory highlights that genetic drift plays a crucial role in shaping allele frequencies within populations, especially in small populations where random events can significantly influence genetic outcomes. By emphasizing the importance of neutral mutations, this theory suggests that many observed patterns of genetic variation may arise not from adaptive changes but from chance events. This shift in perspective has led to more nuanced models of population genetics and evolutionary dynamics.
Evaluate the significance of Motoo Kimura's concept of the 'molecular clock' and its impact on evolutionary biology.
The concept of the 'molecular clock', introduced by Motoo Kimura, is significant because it allows scientists to estimate divergence times between species based on the rate of neutral mutations. This approach has had a profound impact on evolutionary biology by providing a quantitative method to trace evolutionary relationships and timelines. It enables researchers to construct phylogenetic trees and understand how species have evolved over millions of years, contributing greatly to our knowledge of biodiversity and evolution.
A change in the DNA sequence that does not affect an organism's fitness and is neither advantageous nor disadvantageous.
Genetic Drift: A mechanism of evolution that refers to random fluctuations in allele frequencies within a population, often having a more pronounced effect in small populations.