Questions CD's view in Origin that domestic dogs are not descended from a single stock. Occasional crossings of domestic stock with wild species could explain cases of reversion towards wild specific forms. CD's views on hybridity do not then have to be contradicted in constructing an ancestral stock.
Nov. 21— 1859—
The admission which I least like among your familiar illustrations is that while the various pigeons have descended from one stock the dogs have come from two or more species
It seems to me that an occasional cross with some one of the several wolves, the grey & the prairie wolf or even perhaps some foxes & more distant species of the canine genus would have served all the purposes you require. Let these have been more frequent than in the case of most domestic animals, let the hybrid have always interbred with one of the pure parent stock but the infusion of the foreign blood into the domesticated wolf, or whatever single species the dog came from, may have given rise to a tendency to reversion to some of the ancestral crosses why should not they satisfy all your well-ascertained facts, leaving your canons of variation & hybridity unshaken. It is for the followers of Pallas to prove their opinion by some facts. The period of gestation of the dog & the wolf, if as constant as Bell believes, is a strong argument. As Bransby Cooper was a six month's child, I doubt not you can find great occasional irregularity in the gestation of domestic animals & of Man—but still it is surely worth a good deal.—
- f1 2540a.f1See letter to Charles Lyell, 25 October , and letter from Charles Lyell, 28 October 1859.
- f2 2540a.f2Thomas Bell, citing John Hunter and Nicholas Desmarest, stated that the period of gestation is the same in the dog and wolf: 63 days (Bell 1837, pp. 197–8). In C. Lyell 1853, pp. 584–5, Lyell cited Bell's opinion ‘that all the various races of dogs have descended from one common stock, of which the wolf is the original source.’ The use of gestation as a leading criterion for defining species was introduced by Johann Friedrich Blumenbach.
- f3 2540a.f3Bransby Blake Cooper was a surgeon at Guy's Hospital, London, until his death in 1853. He had been born prematurely in 1792.
- f4 2540a.f4In the second edition of Origin, CD modified his statements about the origin of domestic dogs to take account of Lyell's information, yet still maintained his opinion that they had descended from several wild species. The sentence in the first edition of Origin, p. 17, reads: ‘I do not believe, as we shall presently see, that all our dogs have descended from any one wild species’. In the second and subsequent editions, this was altered to: ‘I do not believe … that the whole amount of difference between the several breeds of the dog has been produced under domestication; I believe that some small part of the difference is due to their being descended from distinct species.’ (Peckham ed. 1959, p. 90).