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On the modification of a Race of Syrian Street-Dogs by means of Sexual Selection by Dr Van Dyck. With a preliminary notice by Charles Darwin, F.R.S.

Most of the naturalists, who admit that natural selection has done been much effective on the formation of species, most likewise admit, as I believe that the weapons of male animals are the result of sexual selection,─ that is of the best-armed males obtaining most females & transmitting their masculine superiority to their male offspring.

But many naturalists doubt or deny that female animals even exert any choice & select certain males in preference to others. It would however probably be more correct to speak of the females as being excited or attracted in an especial degree by the appearance, voice &c of certain males, rather than of deliberately selecting them. (a) (text) In order to ascertain whether female animals ever or often exhibited a decided preference for certain males, I formerly enquired from some of the greatest breeders in England, who had no theoretical views to support

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(a) (text)

I may perhaps be here permitted to say that, after having carefully weighed to the best of my ability the various arguments which have been advanced against the principle of sexual selection, I remain firmly convinced of its truth. It is, however, probable that I may have extended it too far, as, for instance, in the case of the strangely formed horns and jaws of male Lamellicorn beetles, which have recently been discussed with much ability knowledge by W. von Reichenau─), & about which I have always felt some doubts. On the other hand, the explanation of the development of the horns offered by this entomologist does not seem to me at all satisfactory.

(footnote)

*Ueber den Ursprung der secundären männlichen Geschlechts-charakteren &c.," Kosmos V Jahrgang 1881, p. 172.

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what their & who had ample experience; had taught them on this head ; & I have given their answers, as well as some published statements, in my Descent of Man.* The facts there given clearly show that with dogs & other animals, the females sometimes prefer in the most decided manner particular males; th but that it is very rare when a male will not accept any female, though such cases do occur. The following statement, taken from the Voyage of the Vega, ** indirectly supports in a striking manner the same above conclusion. Nordenskiöld says:—"We had two Scotch collies with us on the Vega. They at first frightened the natives very much with their bark. To the dogs of the Chukches they soon took the same superior standing as the European claims for himself in relation to the savage. The dog was distinctly preferred by the female Chukch canine population, and that too without the fights to which such favour on the part of the fair commonly gives rise. A numerous canine progeny of mixed Scotch-Chukch breed has arisen at Pitlekaj. The young dogs had a complete resemblance to their father; and the natives were quite charmed with them.")

[The quotation is in the hand of Emma Darwin]

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*The Descent of Man. Second Edit. 1874. p part II. Ch. XVII. p. 522–525. See, also, Ch. XIV on choice in pairing shown by female birds, & on their appreciation of beauty.

** The Voyage of the Vega. Eng. translat. 1881, Vol. II. p. 97.─

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(What the attractions may be which give an advantage to certain males in wooing in the above several cases,─whether general appearance, such as colour & form, or vigour and strength, or gestures, voice, or odour ─ can rarely be even conjectured. But whatever they may be, they would be preserved & augmented in the course of successive generations, if the females of the same species or race, inhabiting the same district, retained during successive generations approximately the same general disposition & taste; & this does not seem improbable. Nor is it indispensable that all the females should have exactly the same tastes: one female might be more attracted by some one characteristic in the male, & another female by a different one; & both, if not incompatible, would be gradually acquired by the males. Little as we can judge what are the characteristics which attract the female; yet, in some of the cases recorded by me, it seemed clearly to be colour; in other cases previous familiarity with a particular male; in others exactly

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the reverse or novelty. With respect to the first appearance of the peculiarities which are afterwards augmented through sexual selection, this of course depends on the strong tendency in all the parts of all organisms to present slight individual differences, & in some organisms to vary in a plain manner. Evidence has also been given in my book on Variation under Domestication showing that male animals are more liable to vary than females; & this would be highly favourable to the kind of sexual selection. Manifestly every slight individual difference & each more conspicuous variation depends on definite though unknown causes; & these aberrations or changes modifications of structure &c. differ in different species under apparently the same conditions. Statements of this nature made by more have sometimes been misinterpreted, as I if it were supposed that variations of all V. were indefinite or fluctuating, & that the similar same variations occurred in all species.) (In reference to sexual selection, I

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will here only add that the complete manner in which the introduced dogs & other domestic animals in S. America & other countries have been mongrelized, so that all traces of their original race have been lost, often appeared to me a surprising fact. This holds good, according to Rengger* with the dogs even in so isolated a country as Paraguay. I formerly attributed this mongrelization merely to the breeds not having been kept separate & to the greater vigour of cross-bred animals offspring; but if the females often prefer strangers to their old companions, as seems to be the case, according to Nordenskiöld, in Siberia, & in Syria, as shown in the following essay, then we can readily understand how rapid & complete will have been would be the process progress of mongrelization. I will now give without further comment the essay which Dr. W. Van Dyck, Lecturer on Zoology to the Protestant College at Beyrout, who has had excellent opportunities for observations during a residence of 20 years, at Beyrout has been so kind as to send me.)

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footnote

* Naturgesichte der Saugethiere von Paraguay 1830 p. 154.