Editing Fleeming Jenkin (section)

== Darwin and evolution ==

In June 1867, Jenkin reviewed [[Charles Darwin|Darwin's]] ''[[On the Origin of Species]]'' (1859), in ''The North British Review''.<ref>[http://www.victorianweb.org/science/science_texts/jenkins.html Jenkin, Fleeming, Review of 'The origin of species', The North British Review, June 1867, 46, pp. 277-318.]</ref> Jenkin criticized Darwin's evolutionary theory by suggesting that Darwin's interpretation of [[natural selection]] couldn't possibly work, as described, if the reigning hypothesis of inheritance, [[blending inheritance]], was also valid. Though [[Gregor Mendel]]'s [[Particulate inheritance|theory of ''particulate inheritance'']] had been already published two years earlier (and would eventually be adopted as the dominant theory of inheritance), neither Jenkin nor Darwin would ever read it, and it would still be several decades before the blending inheritance model would be overturned in the scientific community. In this interim, Jenkin provided a mathematical argument, the [[swamping argument]], that showed that under the blending inheritance model any advantageous mutations which might arise in a species would be quickly diluted out of any species after just a few generations. By contrast, Darwin's interpretation of natural selection required hundreds, if not thousands of generations of passing down such mutations in order to work. Jenkin thus concluded that natural selection could not possibly work if blending inheritance were also true. Despite Jenkin's argument containing a mistake, as A.S. Davis pointed out in 1871,<ref>{{Cite journal |last=Davis |first=A. S. |date=December 1871 |title=The "North British Review" and the Origin of Species |journal=Nature |language=en |volume=5 |issue=113 |pages=161 |doi=10.1038/005161b0 |issn=1476-4687|doi-access=free |bibcode=1871Natur...5..161D }}</ref> it did not affect Jenkin's conclusion, nor mitigate the damage of Jenkin's criticisms of Darwin's ideas during the few decades when blending inheritance was still widely accepted.<ref>{{cite journal | title=Did Jenkin's swamping argument invalidate Darwin's theory of natural selection? | author=Bulmer, M. | journal=[[British Journal for the History of Science]] | volume=37 | pages=281–297 | year=2004 | doi=10.1017/S0007087404005850 | issue=3}}</ref>

Jenkin also referred to Lord Kelvin's recent (incorrect) estimation of the age of the earth. Kelvin had calculated that Fourier's theory of heat and the actions of tides on the earth's rotation allowed for an earth no more than 100 million years old and doubted in so far the case for evolution based on the chronology.<ref>{{Cite book|url=https://books.google.com/books?id=s4AWPFdyrWIC|title=Lord Kelvin and the Age of the Earth|last=Burchfield|first=Joe D.|date=1990-05-15|publisher=University of Chicago Press|isbn=9780226080437|language=en}}</ref> Criticism by Jenkin and [[Alfred William Bennett|A.W. Bennett]], in fact, led Darwin to investigate and discuss the mechanism of inheritance more thoroughly. Darwin avoided a direct confrontation (as well in the case of chronology), but confessed that some of Jenkin's arguments were troubling—so troubling, in fact, that Darwin largely abandoned blending inheritance as the potential mechanism for his own inheritance model, [[pangenesis]], in favor of a competing model of inheritance that derived from [[Lamarckism]].<ref name=dc>{{ cite book |last=Eiseley  |first=Loren |title=Darwin's Century |url=https://archive.org/details/darwinscenturye000eise  |url-access=registration  |date=1961 |publisher=Anchor Books (Doubleday) |page=[https://archive.org/details/darwinscenturye000eise/page/209 209] ff|isbn=9780385081412 }}</ref>