In Memoriam William (Bill) G. Hill
A tribute to Professor William (Bill) Hill, by Brian Charlesworth.
Bill Hill died on December 17, 2021, aged 81. Bill was a world leader in population and quantitative genetics. He spent nearly all his career in Edinburgh, after a first degree in agriculture from the University of London and an MS from the University of California at Davis in 1963.
His PhD supervisor was Alan Robertson, then the most renowned population and quantitative geneticist in Britain.
On getting his PhD in 1965, he was appointed as an assistant lecturer in genetics, and rose through the ranks to become Professor of Animal Genetics (a personal chair) in 1983.
He took on increasingly senior administrative roles, becoming Head of the Division (now School) of Biological Sciences in 1993, and finally Dean of the Faculty (now College) of Science and Engineering.
Despite these heavy burdens, he maintained a steady research output, and took early retirement in 2003 in order to devote himself to his research and related activities (he was a sought-after consultant to the animal breeding community), collaborating successfully with people all over the world.
His teaching was mostly at the postgraduate level, involving both taught courses in Edinburgh, Europe and the USA, and at the PhD level (he supervised more than 50 PhD students). He was an outstandingly successful mentor to research students and postdocs, four of whom have become Fellows of the Royal Society.
He received many honours: FRSE (1979), FRS (1985), OBE (2004), Royal Medal of the RSE (2005), Fisher Memorial Lecturer (2014), Darwin Medal of the Royal Society (2018) and Mendel Medal of the Genetics Society (2019).
Bill’s parents were Scots who moved south during the 1930s, and owned a farm near St. Albans, 20 miles north of London.
Bill maintained a life-long interest in agriculture, and inherited the family farm, which he ran through a manager until selling it several years ago.
He and his family lived for many years in a large Victorian terrace house, a few minutes walk from King’s Buildings, which suited his dedication to his work. He is survived by his wife, Rosemary, and three children.
Leader in population and quantitative genetics
Bill had an international reputation as a formidable quantitative thinker, with a long list of stellar contributions to population genetics, quantitative genetics and animal breeding.
Bill did work of fundamental importance on linkage disequilibrium (LD) – non-random associations between genetic variants at different sites in the genome.
Bill’s 1968 paper (with Alan Robertson) provided a basic framework for understanding how random fluctuations in genotype frequencies due to finite population size causes LD.
This process has turned out to be the major component of observed LD among DNA sequence variants.
Modern methods for studying DNA sequence variability on a genome-wide scale involve the use of LD as an immensely important tool for human and applied geneticists seeking to map and identify genetic factors causing variation in complex traits, many of which are medically or agriculturally significant.
This work is based on the foundations that Bill laid down in the 1960s.
For his PhD work, Bill developed models of the effects of LD on the effectiveness of selection, showing that genetic linkage between variants under selection impedes the ability of the population to respond.
This is because randomly generated LD can cause a beneficial variant at one genomic location to become associated with a harmful variant elsewhere in the genome, the Hill-Robertson effect.
This name was invented by Joe Felsenstein in 1974, in a seminal paper on the evolutionary advantages of genetic recombination.
Bill’s 1966 paper (again with Alan) has been extremely influential for research on this topic, and is widely cited in contemporary papers on population genomics.
Bill was an extremely modest person, and was somewhat embarrassed by the fame of this work – he used to say “I am only an old animal breeder”.
Modelling the behaviour of genes in populations
The main thrust of Bill’s research used mathematical and computer models of the behaviour of genes in populations, in order to understand the genetic basis of quantitatively varying traits such as body size, and their responses to artificial and natural selection. Such traits are of prime importance for evolution, animal and plant breeding, and human health.
Darwin used evidence from artificial selection and quantitative trait variation as the basis for his theory of evolution by natural selection (see the first chapter of The Origin of Species), as was often mentioned by Bill.
Bill was a leader in extending the models introduced by the pioneers of this field (Fisher, Haldane and Wright), as was Alan Robertson.
He made very important contributions to our understanding of the forces (mutation, selection and finite population size) controlling genetic variation in quantitative traits and their response to selection.
In particular, he was the first to quantify the role of new mutations in producing the variability needed for continued responses to selection.
This work has provided both experimental and theoretical confirmation of what Darwin called “the power of selection”, showing that a sustained pressure of selection can produce almost indefinite changes, similar to those observed over much greater timespans in the fossil record.
Impact on Livestock Breeding
In addition to this work in basic science, Bill made many important contributions to the theory of animal improvement, which have had a major impact on livestock breeding.
He was also very active in serving on government and industry committees relating to animal breeding issues.
Deborah and I remember staying on a dairy farm in Lancashire for one night on our way up to Edinburgh in 1994. The farmer proudly showed us his rather hi-tech equipment for monitoring the productivity of the cows, and knew Bill’s name from training sessions he had attended.
Genetics Society - Mendel Medal
Sadly, Bill’s last two and half years were marked by increasing cognitive decline associated with vascular dementia, which came on in the spring of 2019.
Happily, he was able to enjoy the Genetics Society Edinburgh centennial meeting in November 2019, at which he was presented with the Mendel Medal, although he could not deliver the customary lecture.
Instead, Trudy Mackay gave a touching eulogy. He was very realistic about his illness, recognising that life is just a limited interval of consciousness between two darknesses, but it was a heavy blow to someone whose working life was devoted to intense thinking about difficult scientific problems.
A set of pieces by his colleagues and friends celebrating his achievements and personality has been compiled by Kay Boulton, the Secretary of the Genetics Society.