Hostname: page-component-7c8c6479df-24hb2 Total loading time: 0 Render date: 2024-03-18T16:25:55.953Z Has data issue: false hasContentIssue false

Did Jenkin's swamping argument invalidate Darwin's theory of natural selection?

Published online by Cambridge University Press:  01 September 2004

MICHAEL BULMER
Affiliation:
The Old Vicarage, Chittlehampton, Umberleigh, EX37 9RQ, UK.

Abstract

Fleeming Jenkin's swamping argument (1867) is re-examined in relation to subsequent criticisms of its assumptions. Jenkin's original argument purported to show that, under blending inheritance, natural selection could not operate on ‘sports’ or ‘single variations’. A serious flaw in Jenkin's model was exposed in a forgotten paper in 1871. Darwin accepted Jenkin's ‘flawed’ conclusion, though he did not fully understand the argument. Both Jenkin and Darwin regarded the swamping argument as a barrier to evolution within a single lineage. A completely different interpretation of the phrase ‘swamping argument’, first put forward by Romanes in 1886, identified it with the problem of the role of free intercrossing in preventing speciation. The latter problem also underlies current debate about the possibility of sympatric speciation and is as serious under particulate as under blending inheritance. Jenkin's argument depended on the assumption of blending inheritance; when modified to remove the ‘flaw’ in his model, it ceased to present a barrier to the operation of natural selection within a lineage, provided that the mutation rate was high enough to maintain adequate genetic variability under blending.

Type
Research Article
Copyright
2004 British Society for the History of Science

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

I thank Jonathan Hodge and my referees for valuable comments.