THE DEVELOPMENT OF POPULATION
GENETICS
Margaret Morrison
Genetics, like many other sciences that underwent rapid and extensive devel-
opment in the twentieth century, now encompasses a broad range of topics and
fields. Instead of genetics being considered as a branch of biology it is now a
full fledged science in its own right. Although typically concerned with the prob-
lems of heredity and variation, genetics has developed in primarily six different
directions, the oldest beingexperimental breedingwhich dates back hundreds of
years and involves the study of several generations of plants and animals. It relies
primarily on statistical methods as its standard research methodology. Pedigree
analysis, which shows the inheritance of specific traits traced along members of a
family line, is frequently used in cases where experimental breeding isn’t practical.
Cytologystudies the chromosomes and cellular infrastructure that are the keys to
heredity whilebiochemistry(specifically molecular biology) investigates the nature
of genes themselves, how they function and reproduce. An analysis of gene action
allows us to chart the course of amino acid breakdown in cells and determine how
abnormalities arise when a gene fails to produce a particular enzyme.Population
geneticsdeals with the distribution of genes in different populations and traces
population migration and mixing of races by analysing the frequency of various
blood antigens. These same methods allow for the analysis of fossil genetic ma-
terial used for tracing the process of heredity over thousands of years. Finally,
genetic recombinationprovides the foundation for extensive and detailed maps of
the nucleotide sequences of gene molecules which form the basis of the human
genome project.
Just as in history and philosophy of physics where debates about who “dis-
covered” a particular particle or who first used a particular term are part of the
landscape, so too in discussions of genetics; debates about its discovery, who first
used the phrase and whether Mendel was really the founder of what came to be
called Mendelian genetics are not uncommon. These are not the kinds of issues I
will be concerned with here. Instead my focus is on the origins and development
of population genetics up to 1930; a story that deals specifically with the fusion
of Darwinian natural selection with Mendelian genetics into a theory that could
explain what Darwinism couldn’t — variation in a population. The development
of population genetics is also important because it was able to provide knowl-
edge about heritable traits that were simply outside the grasp of the experimental
breeder. Its success was in due, in part, to sophisticated statistical/mathematical
General editors: Dov M. Gabbay,
©c2007 Elsevier B.V. All rights reserved.
Handbook of the Philosophy of Science. Philosophy of Biology
Volume editors:
Paul Thagard and John WoodsMohan Matthen and Christopher Stephens