Mendelian genetics in the context of Boveri–Sutton chromosome theory

The modern synthesis was the early 20th-century synthesis of Charles Darwin's theory of evolution and Gregor Mendel's ideas on heredity into a joint mathematical framework. Julian Huxley coined the term in his 1942 book, Evolution: The Modern Synthesis. The synthesis combined the ideas of natural selection, Mendelian genetics, and population genetics. It also related the broad-scale macroevolution seen by palaeontologists to the small-scale microevolution of local populations.

The synthesis was defined differently by its founders, with Ernst Mayr in 1959, G. Ledyard Stebbins in 1966, and Theodosius Dobzhansky in 1974 offering differing basic postulates, though they all include natural selection, working on heritable variation supplied by mutation. Other major figures in the synthesis included E. B. Ford, Bernhard Rensch, Ivan Schmalhausen, and George Gaylord Simpson. An early event in the modern synthesis was R. A. Fisher's 1918 paper on mathematical population genetics, though William Bateson, and separately Udny Yule, had already started to show how Mendelian genetics could work in evolution in 1902.

Particulate inheritance is a pattern of inheritance discovered by Mendelian genetics theorists, such as William Bateson, Ronald Fisher or Gregor Mendel himself, showing that phenotypic traits can be passed from generation to generation through "discrete particles" known as genes, which can keep their ability to be expressed while not always appearing in a descending generation.

Sir Ronald Aylmer Fisher FRS (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. He has been described as "a genius who almost single-handedly created the foundations for modern statistical science" and "the single most important figure in 20th century statistics". In genetics, Fisher was the one to most comprehensively combine the ideas of Gregor Mendel and Charles Darwin, as his work used mathematics to combine Mendelian genetics and natural selection; this contributed to the revival of Darwinism in the early 20th-century revision of the theory of evolution known as the modern synthesis. For his contributions to biology, Richard Dawkins declared Fisher to be the greatest of Darwin's successors. He is also considered one of the founding fathers of Neo-Darwinism. According to statistician Jeffrey T. Leek, Fisher is the most influential scientist of all time on the basis of the number of citations of his contributions.

From 1919, he worked at the Rothamsted Experimental Station for 14 years; there, he analyzed its immense body of data from crop experiments since the 1840s, and developed the analysis of variance (ANOVA). He established his reputation there in the following years as a biostatistician. Fisher also made fundamental contributions to multivariate statistics.

George John Romanes FRS (20 May 1848 – 23 May 1894) was a Canadian-Scots evolutionary biologist and physiologist who laid the foundation of what he called comparative psychology, postulating a similarity of cognitive processes and mechanisms between humans and other animals.

He was the youngest of Charles Darwin's academic friends, and his views on evolution are historically important. He popularized the term neo-Darwinism, which in the late 19th century was considered as a theory of evolution that focuses on natural selection as the main evolutionary force. Romanes' early death was a loss to the cause of evolutionary biology in Britain. Within six years Mendel's work was rediscovered, and a whole new agenda opened up for debate.