Motoo Kimura facts for kids
Quick facts for kids
Motoo Kimura
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| Born | November 13, 1924 Okazaki, Japan
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| Died | 13 November 1994 (aged 70) |
| Nationality | Japanese |
| Alma mater | University of Wisconsin |
| Known for | Neutral theory of molecular evolution |
| Spouse(s) | Hiroko Kimura |
| Children | 1 |
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| Scientific career | |
| Fields | |
| Institutions | National Institute of Genetics |
| Thesis | Stochastic Processes in Population Genetics (1956) |
| Doctoral advisor | James F. Crow |
| Other academic advisors |
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| Influences | Sewall Wright |
| Influenced | Tomoko Ohta |
Motoo Kimura (木村 資生, Kimura Motō) (November 13, 1924 – November 13, 1994) was a famous Japanese biologist. He is best known for creating the neutral theory of molecular evolution in 1968. This idea changed how scientists thought about how life changes over time at a tiny, molecular level. Kimura was one of the most important thinkers in population genetics, which is the study of how genes change in groups of living things.
He used clever math, like diffusion equations, to figure out how likely different versions of genes (called alleles) were to spread or disappear in a population. He combined his math skills with new information about molecular evolution. This led him to develop the neutral theory. This theory suggests that genetic drift (random changes in gene versions) is the main reason why gene frequencies change at the molecular level.
A well-known geneticist named James F. Crow said that Kimura was one of the two greatest evolutionary geneticists. He put Kimura in the same group as famous scientists like Ronald Fisher, J. B. S. Haldane, and Sewall Wright.
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Life and Work
Motoo Kimura was born on November 13, 1924, in Okazaki, Aichi Prefecture, Japan. From a young age, he loved botany, which is the study of plants. He was also very good at mathematics. He even taught himself geometry while recovering from food poisoning.
After joining a special high school in Nagoya, Kimura focused on how plants are shaped and their cells (cytology). He worked in a lab studying the chromosome structure of lilies. Here, he found a way to connect his love for plants and math through biometry, which uses statistics in biology.
Early Studies and War Time
Because of World War II, Kimura left high school early in 1944 to attend Kyoto University. A famous geneticist, Hitoshi Kihara, advised him to study botany. This choice helped him avoid military duty. After the war, he joined Kihara's lab. There, he learned about adding foreign chromosomes to plants and the basics of population genetics.
In 1949, Kimura started working at the National Institute of Genetics in Mishima, Shizuoka. In 1953, he published his first important paper on population genetics. In this paper, he described a "stepping stone" model. This model helped explain how genes move between different groups of living things. It was more complex than earlier models.
Studying in the United States
After meeting an American geneticist named Duncan McDonald, Kimura arranged to study in the United States. He went to Iowa State University in 1953 to learn from J. L. Lush.
However, Kimura soon found Iowa State too limiting. He moved to the University of Wisconsin. There, he worked on mathematical models with James F. Crow. He also joined a strong group of geneticists, including Sewall Wright, who greatly influenced him.
Near the end of his studies, Kimura presented a paper at a science meeting in 1955. Even though it was mathematically complex and his English was hard to understand, it received high praise from Wright and later J.B.S. Haldane.
Key Contributions in Genetics
At Wisconsin, Kimura developed a general model for genetic drift. This model could include many different gene versions, natural selection, movement of genes, and mutations. He also built on Wright's work by using a new mathematical tool called the Kolmogorov backward equation. This allowed him to calculate the chance of a gene version becoming fixed (meaning it's the only one left) in a population. He earned his PhD in 1956 and then returned to Japan, where he stayed at the National Institute of Genetics for the rest of his life.
Kimura worked on many different problems in theoretical population genetics. Many of these were with his colleague Takeo Maruyama. He introduced important models of mutation, such as the "infinite alleles" and "infinite sites" models. These models became widely used as the field of molecular evolution grew. This growth happened as more information about protein and genetic sequences became available.
The Neutral Theory of Molecular Evolution
The year 1968 was a major turning point for Kimura. In that year, he introduced the neutral theory of molecular evolution. This theory suggests that at the molecular level (like in DNA and proteins), most genetic changes are "neutral." This means they don't give an advantage or disadvantage in terms of natural selection. Because of this, genetic drift (random changes) becomes the main force driving evolution at this tiny level.
The field of molecular biology was growing fast, and there was a debate between scientists who focused on tiny molecules and those who studied whole organisms. The neutral theory was immediately debated. Many molecular biologists supported it, while many evolutionary biologists disagreed.
Kimura spent the rest of his life developing and defending the neutral theory. As James Crow said, much of Kimura's earlier work was perfectly suited for studying neutral evolution. As new experiments and genetic knowledge became available, Kimura expanded his theory. He also created mathematical ways to test it against new evidence. In 1983, Kimura wrote a major book about his theory called The Neutral Theory of Molecular Evolution. He also promoted his ideas through popular writings, like My Views on Evolution, which became a best-seller in Japan.
Even though it can be hard to test against other ideas, the neutral theory is now an important part of how we understand molecular evolution today.
Later Life and Legacy
In 1992, Kimura received the Darwin Medal from the Royal Society. The next year, he became a Foreign Member of the Royal Society.
Later in his life, Kimura suffered from a disease that caused his muscles to weaken, called amyotrophic lateral sclerosis. On November 13, 1994, he had an accidental fall at his home in Shizuoka, Japan. He hit his head and died from bleeding in his brain. He was married to Hiroko Kimura, and they had one son, Akio, and a granddaughter, Hanako.
Honors and Awards
- 1959 – Genetics Society of Japan Prize
- 1965 – Weldon Memorial Prize, Oxford
- 1968 – Japan Academy Prize
- 1973 – Foreign member of the National Academy of Sciences of the USA
- 1976 – Person of Cultural Merit
- 1976 – Order of Culture
- 1982 – Member of the Japan Academy
- 1986 – Chevalier de l'Ordre Nationale de Merite
- 1986 – Asahi Prize
- 1987 – John J. Carty Award of the National Academy of Sciences in evolutionary biology
- 1988 – International Prize for Biology
- 1992 – Darwin Medal
- 1993 – Foreign member of Royal Society
See also
Images for kids
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Motoo Kimura
