Wright and Fisher on inbreeding and random drift.

Sewall Wright and R. A. Fisher often differed, including on the meaning of inbreeding and random gene frequency drift.

On epistasis: why it is unimportant in polygenic directional selection.

There is a difference in viewpoint of developmental and evo-devo geneticists versus breeders and students of quantitative evolution. The former are interested in understanding the developmental process; the emphasis is on identifying genes and studying their action and interaction. Typically, the genes have individually large effects and usually show substantial dominance and epistasis.

Mayr, mathematics and the study of evolution.

In 1959 Ernst Mayr challenged the relevance of mathematical models to evolutionary studies and was answered by JBS Haldane in a witty and convincing essay. Fifty years on, I conclude that the importance of mathematics has in fact increased and will continue to do so.

Maintaining evolvability.

Although molecular methods, such as QTL mapping, have revealed a number of loci with large effects, it is still likely that the bulk of quantitative variability is due to multiple factors, each with small effect. Typically, these have a large additive component. Conventional wisdom argues that selection, natural or artificial, uses up additive variance and thus depletes its supply.

Mid-century controversies in population genetics.

Beginning in the 1930s, evolution became an experimental subject. New techniques, especially in Drosophila, made possible quantitative analysis of natural populations. In addition to a large number of studies on many species, there were four major controversies that dominated much of the discussion and experimentation.

Inferring purging from pedigree data.

The harmful effects of inbreeding can be reduced if deleterious recessive alleles were removed (purged) by selection against homozygotes in earlier generations. If only a few generations are involved, purging is due almost entirely to recessive alleles that reduce fitness to near zero. In this case the amount of purging and allele frequency change can be inferred approximately from pedigree data alone and are independent of the allele frequency.

Age and sex effects on human mutation rates: an old problem with new complexities.

Base substitution mutations are far more common in human males than in females, and the frequency increases with paternal age. Both can be accounted for by the greater number of pre-meiotic cell divisions in males, especially old ones. In contrast, small deletions do not show any important age effect and occur with approximately equal frequency in the two sexes.

Timeline: Hermann Joseph Muller, evolutionist.

This essay is dedicated to the proposition that Hermann Joseph Muller, widely regarded as the greatest geneticist of the first half-century of the subject, was also one of the greatest evolutionists of this period. His Nobel Prize-winning work, which showed that radiation increases the mutation rate, is in every genetics textbook, and his prescient ideas have influenced almost every aspect of the discipline. Here I emphasize his less well-known contribution to the neo-Darwinian theory of evolution.

Essay: early American genetics journals.

Before the Second World War, there were only two North-American journals exclusively devoted to genetics - the Journal of Heredity and Genetics. In the late 1940s, Genetics spawned two progeny - the American Journal of Human Genetics and Evolution. This article recounts the early days of these journals, their influential and often colourful founding editors, and their contents.