The 1999 Genetics Society of America Medal
Jan Drake

Charles H. Langley. Photo courtesy of Stacia Langley.

CHARLES HUNT LANGLEY was awarded the 1999 Genetics Society of America Medal in recognition of his contributions to our understanding of genetic variation in natural populations and the population biology of parasitic transposable elements. Chuck has conducted seminal investigations that helped to reveal how polymorphism frequencies vary across the genome and helped to document the molecular basis of natural phenotypic variation. In the course of this work, he trained an entire school of investigators in the use of molecular-genetic methods of analysis in population genetics and dispersed them worldwide, many of whom now occupy key positions in major research institutions.

Chuck took his doctoral degree at the University of Texas at Austin with Ken Kojima and then did postdoctoral work at the University of Wisconsin at Madison with Jim Crow. In 1973, he joined the genetics community at the national Institute of Environmental Health Sciences (NIEHS), where he stayed until moving to the University of California at Davis in 1989. Following a long tradition among experimental population geneticists, he has consistently used Drosophila as his system of choice.

In years-long collaborations with Walter Fitch and John Gillespie, Chuck showed that the evolutionary molecular clock is substantially more erratic than had been suspected, contradicting some of the more simple versions of the theory of neutral molecular evolution. Walter remembers that Chuck did all the math and theory for their papers and introduced Walter to the wonders of maximum likelihood. Moving from the widely used one-dimensional systems for displaying protein mobility variants, Chuck, Andy Leigh Brown, and others adapted two-dimensional displays to show that levels of polymorphism in Drosophila's coding regions had been systematically overestimated. Working with Bob Voelker and others, Chuck showed that frequencies of null alleles in natural Drosophila populations can be explained by classical mutation-selection balance with average selection coefficients of about 10−3; this value convincingly demonstrated the near impossibility of directly estimating selection on electromorphs. Chuck performed some of the first large-scale surveys of polymorphisms in nuclear DNA using restriction enzymes. With Brian Charlesworth and Norm Kaplan he described natural variation in transposable element number and position and offered an attractive explanation for their distribution. More recently, Chuck and his collaborators showed that frequencies of DNA polymorphisms decrease in regions of the genome that have lower rates of crossing over, and they constructed a plausible theory to explain this effect. This theory, which uses coalescents, grew out of a long-standing collaboration with Dick Hudson. Chuck was among the first to appreciate the important role that coalescent theory plays in population genetics and he has been influential in its development and application. In another long-standing collaboration, with Trudy Mackay, Chuck used a “candidate locus” approach to unravel the molecular basis of phenotypic variation.

Chuck's curriculum vitae reveals a key aspect of his manner. After documenting his existence and education, it appends only two more entries: a brief chronology of employment, and an impressive list of publications. Having been his colleague and nominal chief for a number of years, I know firsthand that there has been far more to his life than these entries reveal. For instance, when the International Program Committees for both the 16th and the 18th International Congresses of Genetics ran into difficulties, my reaction was to assemble a small group of polymaths and ask them to draft an instant program of the highest possible quality. In both instances Chuck played a key role, personally (and until now invisibly) proposing a large portion of each program. It is thus historically just that he himself now chairs the International Program Committee for the 2003 Congress in Melbourne. I also well remember a terrible time in 1987–88 when an NIEHS Scientific Director turned viciously against the institute's genetics community, igniting a battle that fortunately resulted in the Scientific Director's resignation rather than our mass departure. In this battle Chuck once again played a key role, taking over the formal leadership of the community for several months until the drama played out. In the following year Chuck migrated to Davis, where he has continued to prosper.

More recently, Chuck became aware of some of the potential pitfalls of the populational aspects of human genome research. As a result, he has served on several key national committees focused on the kinds of information that must be collected in order to get the most from this huge enterprise.