Darwin's On the Origin of Species. Daniel Duzdevich
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only very slight distinctive characteristics, has a distinct wild prototype. At this rate there must have existed twenty species of wild cattle and sheep – and several goats – in Europe alone, and even several within Great Britain. One author believes that there once existed eleven unique wild sheep species in Great Britain! Britain barely has any unique mammals, France only a few distinct from Germany, and vice versa, and the same is true of Hungary, Spain, and other localities. Yet each of these kingdoms possesses several peculiar breeds of cattle, sheep, and other animals, meaning that many domestic breeds originated in Europe because it lacks sufficient unique species as parent stocks. This is also true for India. Even in the case of the domestic dogs of the whole world, which I admit probably descended from multiple wild species, there has been immense heritable variation. Who can believe that animals closely resembling the Italian greyhound, bloodhound, bulldog, or Blenheim spaniel – so unlike all wild dogs – ever existed in the wild? Crossing a few original dog species would result in only intermediate forms, and accounting for domestic dogs by this process requires the previous existence of extreme forms, similar to the breeds mentioned, in a wild state. In addition, the possibility of generating distinct varieties by crossing is exaggerated. Obviously a variety can be modified by occasional crossing if mongrels with desired characteristics are carefully selected, but a variety intermediate between two extremely different varieties or species could not be obtained. (Sir J. Sebright experimentally attempted precisely this and failed.) The offspring from the first cross between two pure breeds is fairly uniform – and as I have found with pigeons, sometimes very uniform – and everything seems simple enough. But when these mongrels are crossed with one another for several generations, few will be alike and the utter hopelessness of the task becomes apparent. An intermediate between two very distinct breeds could be obtained only with extreme care and continuous long-term selection, but I cannot find a single recorded case of a variety formed this way.
Believing that it is best to study one particular group, after deliberation I took up domestic pigeons. Pigeons have been watched, tended with the utmost care, and loved by many people. They have been domesticated for thousands of years in several parts of the world. Professor Lepsius has pointed out to me that the earliest known record of pigeons is in the fifth Egyptian dynasty (ca. 3000 BC), but Mr. Birch informs me that pigeons are given a bill of fare in the previous dynasty. In Roman times pigeons fetched a high price. Pliny writes, “Nay, they are come to this pass, that they can reckon up their pedigree and race.” The court of India’s Akber Khan (ca. 1600) always traveled with at least twenty thousand pigeons. “The monarchs of Iran and Turan sent him some very rare birds,” and, continues the court historian, “His Majesty, by crossing the breeds, which method was never practiced before, has improved them astonishingly.” At about this same period, the Dutch were as enthusiastic about pigeons as the Romans had been.
I have kept every pigeon breed that I could purchase or obtain and have been kindly favored with skins from several parts of the world, especially by the Hon. W. Elliot from India and the Hon. C. Murray from Persia. Many treatises in several languages have been written about pigeons, some of them very important because of their age. I have consulted several eminent breeders and joined two of the London Pigeon Clubs. The diversity of breeds is astonishing. Compare the English carrier to the short-faced tumbler and see the wonderful differences in their beaks, with corresponding differences in their skulls. The carrier, especially the male, is remarkable for the carunculated skin about its head and the accompanying greatly elongated eyelids, large nostrils, and widely gaping mouth. The outline of the short-faced tumbler’s beak is like that of the finch’s beak, while the common tumbler has the strictly inherited singular habit of flying at a great height in a compact flock and tumbling in the air head-over-heels. The runt is large with a long, massive beak and big feet. Some runt sub-breeds have long necks; others, long wings and tails; still others, short tails. The barb is related to the carrier but has a short and broad beak instead of a long one. The pouter’s body, wings, and legs are elongated; it glories in inflating its enormously developed crop, which may elicit astonishment and even laughter. The turbit has a short and conical beak, with a line of reversed feathers down its breast and a habit of slightly expanding the upper part of its esophagus. The Jacobin has feathers along the back of the neck that are so reversed that they form a hood; for its size, it has relatively elongated wing and tail feathers. The trumpeter and laugher, as their names suggest, coo very differently from the other breeds. The fantail has thirty or even forty tail feathers – even though the normal number in all members of the pigeon family is twelve or fourteen – and they are kept expanded and carried so erect that in good specimens the head and tail touch; the oil gland is aborted. Several other less distinct breeds could be mentioned.
Skeletal structure also differs among breeds. The length, breadth, and curvature of face bones differ enormously. The size and shape of the ramus of the lower jaw, the size and shape of the apertures in the sternum, and the degree of divergence and relative sizes of the two arms of the furcula vary remarkably. The number of caudal and sacral vertebrae; the number of ribs, along with their relative breadth and presence of processes; the proportional width of the mouth; the proportional length of the eyelids, nostrils, tongue – not always in strict correlation with the length of the beak – the size of the crop and the upper esophagus; the development and abortion of the oil gland; the number of primary wing and caudal feathers; the relative lengths of the wings and the tail to each other and to the body; the relative lengths of the legs and feet; the number of scutellae on the toes; and the development of skin between the toes are all structural features that vary. The period at which complete plumage is acquired, the state of the down with which nestlings are clothed when hatched, and the size and shape of the eggs also vary. Flying style and, in some breeds, voice and disposition differ remarkably. Lastly, in certain breeds the males and females have come to differ slightly from each other.
There are at least twenty pigeon breeds that an ornithologist would classify as well-defined species if he were told they were wild birds. I doubt any ornithologist would place the English carrier, short-faced tumbler, runt, barb, pouter, and fantail in the same genus, especially because for each there are several true-breeding sub-breeds, or, as he would call them, species.
Despite the great differences among pigeon breeds, I agree with the common opinion of naturalists that they have all descended from the rock pigeon (Columba livia), a category that includes several geographical varieties or sub-species differing from one another in minor respects. Some of the justifications for this conclusion are somewhat applicable in other cases, so I will briefly give them here. If pigeon breeds are not varieties and have not descended from the rock pigeon, then they must have descended from at least seven or eight original stocks, because it would be impossible to generate the present domestic breeds by the crossing of any fewer. For example, how could a pouter be produced by crossing unless one of the parental stocks possessed the characteristically enormous crop? The supposed original stocks must all have been rock pigeons – that is, not breeding or perching in trees. But besides C. livia only two or three other species of rock pigeon are known, and these lack the characteristics of domestic breeds. Therefore, the supposed original stocks would have to either (1) still exist unknown to ornithologists in the regions where they were first domesticated, or (2) have become extinct. Because of the rock pigeon’s size, habits, and remarkable characteristics, (1) is unlikely. And birds that are good fliers and breed on precipices are unlikely to become extinct. The common rock pigeon has the same habits as the domestic breeds and hasn’t been exterminated on several British islets or the shores of the Mediterranean, making (2) a rash assumption. Furthermore, the above-mentioned breeds have been introduced to all parts of the world, so some of them must have wound up in their supposed native regions, yet not one has ever became wild or feral (although the dovecot pigeon, which is the rock pigeon in a slightly altered state, has become feral in several places). All recent experience demonstrates the difficulty of breeding wild animals in confinement, but the hypothesis of plural origin for domestic pigeons implies that at least seven or eight species were so thoroughly domesticated in ancient times by half-civilized humans that they were quite prolific under confinement.
An important argument, also relevant to other cases, is that although these breeds are generally the same in constitution, habits, voice, coloring, and most structural parts as the wild rock pigeon, they are extraordinarily abnormal in other parts of structure. We could search the