Evolution: The Modern Synthesis

***Evolution: The Modern Synthesis*** is the title of a book by Julian Huxley which was published in 1942. It was the book which gave the modern evolutionary synthesis its name. It was one of the most important books on biology in the mid-twentieth century.

## The background to the book

Huxley was one of the main people behind the new evolutionary synthesis which took place around the time of World War II.

- "The most informative episode in the history of evolutionary biology was the establishment of the 'neo-Darwinian synthesis'." Berry and Bradshaw, 1992. The synthesis was brought about "not by one side being proved right and the others wrong, but by the exchange of the most viable components of the previously competing research strategies". Ernst Mayr, 1980.

### A trial run

Huxley's first 'trial run' was the treatment of evolution in the _Science of Life_ (1929–30). In 1936 he published a long and significant paper for the British Association. In 1938 he wrote three lengthy reviews on major evolutionary topics.

Two of these papers were on the subject of sexual selection. This is an idea of Darwin's which has been revived in recent times. Huxley thought that sexual selection was "...merely an aspect of natural selection". This rather grudging acceptance of sexual selection was influenced by his studies on the courtship of the Great Crested Grebe (and other birds that pair for life). The courtship takes place mostly _after_ mate selection, not before.

### The book and its reception

Now it was time for Huxley to tackle the subject of evolution at full length, in what became the defining work of his life. He had met many of the other people in the debate. His book _Evolution: The Modern Synthesis_ was written whilst he was Secretary to the Zoological Society. It used his remarkable collection of reprints covering the first part of the century. It was published in 1942.

Reviews of the book in learned journals were little short of ecstatic; the American Naturalist called it "The outstanding evolutionary treatise of the decade, perhaps of the century. The approach is thoroughly scientific; the command of basic information amazing".

#### Others in the field

Huxley's main co-respondents in the modern evolutionary synthesis are usually listed as Ernst Mayr, Theodosius Dobzhansky, George Gaylord Simpson, Bernhard Rensch, Ledyard Stebbins and the population geneticists J.B.S. Haldane, Ronald Fisher and Sewall Wright. At the time of Huxley's book several of these had yet to make their distinctive contribution. Certainly, for Huxley, E.B. Ford and his co-workers  in ecological genetics were at least as important.

#### Key terms

It was Huxley who coined the terms _the new synthesis_ and _evolutionary synthesis._  He invented the term _cline_ in 1938 to describe species whose members fall into a series of sub-species with continuous change in characters over a geographical area. The classic example of a cline is the circle of subspecies of the gull _Larus_ round the Arctic zone. This cline is an example of a _ring species_.  Some of Huxley's last contributions to the evolutionary synthesis were on the subject of ecological genetics. He noted how surprisingly widespread polymorphism is in nature, with visible morphism much more prevalent in some groups than others. The immense diversity of colour and pattern in small bivalve molluscs, brittlestars, sea anemones, tubicular polychaetes and various grasshoppers is perhaps maintained by making recognition by predators more difficult.
- Huxley, Julian 1942. _Evolution: the modern synthesis_. Allen and Unwin, London. 2nd ed 1963; 3rd ed 1974.