, (born 1951) is a Japanese

population geneticist Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and popula ...

known for his contributions to coalescence theory. He developed the

test statistic Test statistic is a quantity derived from the sample for statistical hypothesis testing.Berger, R. L.; Casella, G. (2001). ''Statistical Inference'', Duxbury Press, Second Edition (p.374) A hypothesis test is typically specified in terms of a tes ...

now known as

Tajima's D Tajima's D is a population genetic test statistic created by and named after the Japanese researcher Fumio Tajima. Tajima's D is computed as the difference between two measures of genetic diversity: the mean number of pairwise differences and the ...

Biography

Fumio Tajima was born in Ōkawa, in Japan's

Fukuoka prefecture is a Prefectures of Japan, prefecture of Japan located on the island of Kyūshū. Fukuoka Prefecture has a population of 5,109,323 (1 June 2019) and has a geographic area of 4,986 Square kilometre, km2 (1,925 sq mi). Fukuoka Prefecture borders ...

, in 1951. He graduated from high school in 1970, completed his undergraduate degree at

Kyushu University , abbreviated to , is a public research university located in Fukuoka, Japan, on the island of Kyushu. Founded in 1911 as the fourth Imperial University in Japan, it has been recognised as a leading institution of higher education and resear ...

in 1976, and received a

Master's degree A master's degree (from Latin ) is a postgraduate academic degree awarded by universities or colleges upon completion of a course of study demonstrating mastery or a high-order overview of a specific field of study or area of professional prac ...

from the same institution in 1978. Tajima later stated that during his undergraduate degree he studied under Tsutomu Haga, and that he chose to study

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...

after a meeting with him. In 1979 Tajima became a

graduate student Postgraduate education, graduate education, or graduate school consists of Academic degree, academic or professional degrees, certificates, diplomas, or other qualifications usually pursued by higher education, post-secondary students who have ...

at the

University of Texas The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas, United States. Founded in 1883, it is the flagship institution of the University of Texas System. With 53,082 students as of fall 2 ...

Houston Houston ( ) is the List of cities in Texas by population, most populous city in the U.S. state of Texas and in the Southern United States. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the county seat, seat of ...

, where he was supervised by

Masatoshi Nei was a Japanese-born American evolutionary biologist. Professional life Masatoshi Nei was born in 1931 in Miyazaki Prefecture, on Kyūshū Island, Japan. He received a Bachelor of Science degree from the University of Miyazaki in 1953, a ...

. He submitted his

doctoral dissertation A thesis (: theses), or dissertation (abbreviated diss.), is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings.International Standard ISO 7144: D ...

in 1983. Tajima returned to Kyushu university as a visiting scholar in 1983. Beginning in 1989, he worked at the

National Institute of Genetics The National Institute of Genetics is a Japanese institution founded in 1949. The institute is located in Mishima, Shizuoka. It hosts the DNA Data Bank of Japan The DNA Data Bank of Japan (DDBJ) is a biological database that collects DNA seq ...

as an assistant professor and then an associate professor, before moving to the

University of Tokyo The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...

in 1995. There, he became a professor in the Division of Biodiversity and Evolution, a unit of the Department of Biological Sciences. In 2008, he won the Kihara prize awarded by the Genetics Society of Japan. He retired in 2017. As a graduate student, Tajima was one of several researchers working independently on coalescence theory, which seeks to describe the evolutionary history of a single

locus Locus (plural loci) is Latin for "place". It may refer to: Mathematics and science * Locus (mathematics), the set of points satisfying a particular condition, often forming a curve * Root locus analysis, a diagram visualizing the position of r ...

. His training in

phylogenetics In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

and

population genetics Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as Adaptation (biology), adaptation, s ...

put him in a good position to explore evolutionary trees with respect to single loci. In a 1983 paper, published in the journal ''

Genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...

'', Tajima laid out findings that have since been described as among the "most important results in coalescence theory". These included the

mean A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There are several kinds of means (or "measures of central tendency") in mathematics, especially in statist ...

and the

variance In probability theory and statistics, variance is the expected value of the squared deviation from the mean of a random variable. The standard deviation (SD) is obtained as the square root of the variance. Variance is a measure of dispersion ...

of the time between the present and the

most recent common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

. In his paper, Tajima showed that well-known results of "classical" population genetics could be reproduced by using coalescence theory. While doing so, Tajima was likely unaware of the previous work of

John Kingman Sir John Frank Charles Kingman (born 28 August 1939) is a British mathematician. He served as N. M. Rothschild and Sons Professor of Mathematical Sciences and Director of the Isaac Newton Institute at the University of Cambridge from 2001 unt ...

in the same area. The 1983 paper has been described as among the "founding papers of modern population genetics". In 1989 Tajima published another influential paper in ''Genetics''. This paper described a method to use the site frequency spectrum to estimate whether a population is evolving neutrally, evolving under

directional selection In population genetics, directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes. This genetic selection causes the allele frequency to shift toward the ...

, or evolving under

balancing selection Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing ...

. This

, which is known as

, became a widely used test for neutrality among population geneticists.

References

{{DEFAULTSORT:Tajima, Fumio University of Texas Health Science Center at Houston alumni Academic staff of the University of Tokyo Population geneticists Japanese geneticists 1951 births Living people Scientists from Fukuoka Prefecture