Masatoshi Nei (根井正利 Nei Masatoshi?) is Evan Pugh Professor of Biology at Pennsylvania State University and Director of the Institute of Molecular Evolutionary Genetics since 1990. He was born in 1931 in Miyazaki Prefecture, on Kyūshū Island, Japan. He was associate professor and professor of biology at Brown University from 1969 to 1972 and professor of population genetics at the Center for Demographic and Population Genetics, University of Texas at Houston, from 1972 to 1990. He is a theoretical population geneticist and evolutionary biologist. Acting alone or working with his students, he has continuously developed new statistical theories of molecular evolution taking into account frontier knowledge of molecular biology. He has also made several conceptual developments of evolutionary theory.

The basic processes of evolution are changes in gene frequency and the emergence of new types by mutation and gene duplication. Before molecular genetics became established, evolutionary biologists had to make inferences based on phenotypic observations. Molecular genetics has provided the means of assessing the genetical biochemistry behind outward phenotypic differences. This book is an attempt to make molecular population genetics intelligible to both biologists and applied mathematicians. The mathematical sections presuppose a knowledge of calculus and probability theory. Two substantial chapters deal with the mathematical theory of the relevant parts of population genetics. The rest of the book deals, from the molecular genetic standpoint, with evolutionary history, mutation, genetic variability in natural populations, differentiation of populations and speciation, and long-term evolution. As one would expect from his published work, the author considers that data on molecular evolution are more easily explained by the neutral mutation theory than by neo-Darwinism, although he points out that the neutral theory is "heavily dependent on the assumption that the rate of neutral or near-neutral mutations is constant per year rather than per generation."J.D. Turton