Article,
Where biology meets; or how science advances: Presidential Address to the Linnean Society delivered at the Anniversary Meeting, 24th May 1985
Biological Journal of the Linnean Society, 30 (3): 257--274 (1987)
DOI: 10.1111/j.1095-8312.1987.tb00300.x
Abstract
Major advances in ‘unrestricted’ sciences like biology commonly occur when individual scientists (or techniques) cross conventional discipline boundaries; intra-discipline studies are essential for the consolidation and progress of the science, but are less likely to produce significant insights. ‘Restricted’ (or exact) sciences ignore variation, and are probably less sensitive to warping from specialization. This generalization is illustrated by recent controversies in evolutionary biology, particularly the neutralism debates of the 1970s, where over-rigid adherence to theoretical models and unjustified assumptions about the effects of gene action were made. The consequence of some of these is shown by considering genetic changes in house mouse (Mus domesticus) populations which were used to demonstrate apparent drift operating on neutral traits, whereas longitudinal studies of closed populations proved that strong natural selection may operate; a proper understanding of genetical forces requires a knowledge both of the history of particular populations and of environmental pressures varying in time and space.
At the height of neutralist euphoria in the late 1960s and early 1970s, the
house mouse (Mus domesticus)* was frequently quoted as an exemplar of neutral
evolution. The main reason for this was the apparently random variation in
allele frequencies at both the geographical (Wheeler & Selander, 1972) and
ecological levels (Anderson, 1964; Selander, 1970), linked with heterozygote
deficiency and evidence of tight deme structure (Petras, 1967; DeFries &
McClearn, 1972) which indicated that selection was not affecting breeding
success.
The interpretation that genetic variation in the mouse was neutral was wholly
correct from the data available at the time, but in retrospect the data themselves
can be seen to be too limited for firm conclusions. The belief that “the effective
population size in natural populations of house mice is less than four” (DeFries
& McClearn, 1972) was based on laboratory experiments and commensal
populations, whereas virtually every longitudinal study of mice living in a
reasonably stressful environment has shown a degree of population churning.
For example, Lidicker (1976) found a small amount of gene flow between established social groups, and more extensive genetic mixing through the
formation of new social groups.
But even more important, other experiments have provided direct evidence of
selection acting on mice. Rather ironically, at the same time that Petras and
Selander were carrying out their work which indicated that biochemical
variants were non-adaptive in mice, I was studying some of the same variants,
and producing evidence that they were subject to natural selection.
