"...this general & perfect fertility surprising, when we remember how liable we are to argue in a circle on this point; & when we remember that the greater number of varieties have been produced under domestication by man's selection of mere external differences & not of differences in the reproductive system. In all respects, besides fertility, there is a closer general resemblance between hybrids & mongrels. Finally, then, the facts too briefly given in this chapter, do not seem to me opposed, but rather to support the view that there is no fundamental difference between Species & Varieties."
In Chapter 8 of the Origin Darwin addresses a fundamental question: what is a species? He opens the chapter by summarising the generally accepted view that "species, when intercrossed, have been specially endowed with the quality of sterility, in order to prevent the confusion of all organic forms". Darwin knew that this natural boundary was key to any argument about the mutability of species, since it suggested species were independently created, and his chapter on hybridism shows that the true picture is vastly more complicated. The key to understanding species lies in their reproductive systems, not in observable physical differences - an important point that is reiterated in the current leaf of manuscript. He notes that the claim of sterility covers two distinct issues: whether two different species can produce offspring, and whether the resulting hybrids are themselves sterile. Species can be forced to hybridise with human intervention, but in some instances species hybridize naturally if their reproductive systems are sufficiently similar. Nor are all resultant hybrids sterile: horticultural evidence for sterility has been heavily influenced by the conditions in which flowering plants were grown and bred and the likelihood of close interbreeding, which itself results in lower levels of fertility. Darwin does not propose an alternative definition of a species but shows how the complexity and variety of life resists generalities and hard and fast laws; a fact which makes the explanatory power of evolution by natural selection all the more extraordinary.
It is characteristic of Darwin's book that key points are made at the end of chapters, as he gradually builds up his argument, and the final sentence of the current leaf provides the radical conclusion to a chapter that had ranged from Victorian hothouses to speculation on the origin of the domestic dog: "there is no fundamental difference between species & varieties". Darwin's argument that species are not fixed and immutable is key to his profound insight into the nature of life on earth. New species can develop through natural selection by splitting into distinct varieties, which then gradually diverge. The difference between varieties within species (which sometimes have difficulty breeding fertile offspring) and differences between species themselves (which are sometimes able to breed fertile offspring) is one of degree, not of kind.
The text in the current leaf of manuscript is found on pages 277-78 of the first edition of the Origin. The manuscript was written between from July 1858 to April 1859 (see next lot), but Darwin later made extensive stylistic changes in proof so here, as in most other such leaves, the printed text differs in detail from the manuscript. This is the only substantial part of Chapter 8 to survive - the only other known manuscript leaf being Darwin's table of contents of the chapter (Honeyman Collection, now Lehigh University Library).
Darwin had no further use for the draft manuscript once the fair copy had been produced, and, like several other of Darwin's manuscripts, this leaf was later used as scrap paper by the Darwin family. The verso has pencil notes on geometry, later erased but still largely legible, that have been identified as being in the hand of Darwin's son George (1845-1912), who went on to hold a Chair in Astronomy at Cambridge.
THIS IS ONE OF ONLY ELEVEN LEAVES OF THE WORKING MANUSCRIPT OF THE ORIGIN OF SPECIES TO REMAIN IN PRIVATE HANDS (see next lot).
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