PREPOTENCY AND THE MAKING OF NEW BREEDS

New Zealand Mail, Issue 1510, 7 February 1901, Page 52

PREPOTENCY AND THE MAKING OF NEW BREEDS

• Darwin was the first to point out, probably not the first- to notice, that when two greatly differing kinds of the same species bred offspring the latter did not -appear to blend the two parental kinds into one mixture, but took after some -remote common ancestor. This is <:re-

j version,” and! therefore reversion can to j an extent be caused at wall by the /-breeder. B.ut reversion is generally exactly what the breeder of domestic ani_ r male does not -want to produce; for

r- it- may be to ancestors so remote as - to make it problematical whether any of - the desired characteristics of breed will

be maintained. It may, on the other Sand, be to near ancestors, and may be called up by much less drastic means .than that contemplated above, and, it . .-may.* be. then of material use to the / breeder.. We know that- violent crosses

„; produce violent an uncontrolled re- / "suits; and if, therefore, we can by less /.violent changes produce controlled re- , suits of pa. ft rally co jiffioiled; effects, that ,; *& the* sfdgg jbf. breeding most: to; be def/eired; ‘/ I' ''say; stage of breeding ; because "we have never yet in any breed of domess /tic' animals arrived at " a stage • when ". change of variety ceases; Something as always occurring to create change, " and it appears from this that- the first '. law governing the animal kingdom is ' that of variation. The breeders of all varieties of pure-breds haye set tliem/aMves the task bf combating this first e , Jaw'in Nature. They aim. not only - at ' breeding two alike, which, by the way, has never yet' been exactly achieved, but of breeding whole flocks and herds alike. But there is a difference in the aims of breeders of various species; for instance, the breeder of racehorses and greyhounds breeds for change, but airy -Ways change in one direction ; that is c to say, they follow the law of Nature, ; and are its obedient servants, whereas cattle-breeders and fanciers of all classes breed around, a fixed type, and although change does take place very rapidly, it is against- their wish and de_ sire. The choice of mates for what they can do is something like the law of • the survival of the fittest, discovered by

Daman ; but the selection of mates for what they appear to tho eye to be is not based on the previously mentioned law, and - consequently variety comes in a direction that is least wanted. Inbreeding is the expedient bv which breeders seek to prevent change ; and by this means they establish a type which :t is hard to break down, so that a cross with it upon another variety will result in the inbred individual dominating the characteristics of the offspring, unless fine cross is too violent, and reversion is •set up, as it were, by repulsion—the nonunion, or refusal to blend, of two antagonistic varieties.

According to Mr Galt on, the two parents contribute! one-half towards ancestral heredity, the four grandparents one-quarter towards it, the eight great .grandparents one-eighth, the sixteen in the next generation one sixteenth, and so on. This may be/ called a natural, as well as a mathematical. rule of breeding, and probably it holds good: when parents are in no way related to each other] and: also in no way unlike each other; but as these conditions never do Happen,--fine rule itself can never be. ap-

plied except-in its- many- Variations. We have -seen that if violent unlikes beget * offspfiiig, the ? first- /part/-'' of. dire rule breaks down at -once—the parents a-p_ pear to have little or no influence on the characteristics : of their offspring. It is therefore fair to .surmise that if unlikeness destroyed the influence of parents that- likeness between them would;; on the contrary, accentuate it, and this is believed to be a fact-. But there are cases in which unlikeness does not result in the manner described, and therefore it is open to question whether likeness in the- parents always acts in one way either. As to unlikeness, when

a pointer and a setter are crossed to-

gether the young are called' droppers, and in appearance they are not reversions, but, on the contrary, apparently pure-bred! setters and pure-bred pointers, although born at the same time. This

is very remarkable ,and it is apparently open to us to adduce a law of Nature from it, and to restate Mr Gal ton’s law with this variation. The two parents, will influence the offspring between them by one-half; but- this, half may come partly from the'two or wholly from the' one, and when it comes from one the

ancestry of the other has slight, .if any, apparent influence, whereas the ancestry of the: influencing parent is great in proportion as the other’s is little. But although -it- often! happens that the ex_ t-ernal appearance of the dropper is that of pure breed, the descendants from it may revert to the other type, and show a distinct cross, although descended from pure blood in an animal of similar appearance to the dropper parent —that is, two similar parents, one of which is of crossed blood, .may‘ have offspring which revert to the crossed blood. It, therefore, follows that one grandparent may influence the appearance more than both parents together ; and Mr Gallon’s law is again honoured by the breach of it. These are curious contradictions of every law except one —that me named above as the first law in breeding, that everything makes for variation, and that no breed can stand still.

Prepotency of some animals is a generally .admitted fact; and it might be said. , that constant, variation cannot be a law if- there/are instances, in which),similarity of offspring is constant from or.e

parent, no matter how; the, (•,fiher £ parents -differ -fro-m the. .prepotent/one. "But Mr v Gaiton, thinks that- prepotency is a highly heritable “sport,” and Professor Ewart shows that it not infreq.ue.itly accompanies other kinds . of/“sports. * These sports may be' termed spontaneous variations from type without apparent reason, and; when -they are; a.s he .says in common, accompanied! by prepotency, ;we see the very quality of the greatest constancy working in: the direction of change and variety. It was asked ty Lord Salisbury (I think it was) how new varieties could possibly be formed by

.sports; He imagined that one sport would have to seek out another similar .sport of opposite sex before a new type could be evolved from, their u-iion. But Professor Ewart is of opinion that the second sport would not only not assist to establish a -new -type, but would be in the way of it- ;' that prepotency accompanied by a spOrt would stamp itself all

the, more effectually because its mates

were not sports and not prepotent. So that,. instead of prepotency always being 'a means to similarity v df individuals, it may Jbe a means, to. new varieties, and may have been A cause of‘new species

arising out of old and pure-bred raefis. Prepotency is not ‘ always a sport, but may be the result of contimious 'breeding to on© type and likeness for many generations, and when it is so it is again a means to variation, although the reverse is -commonly said, of it. - Bred to animals of its own breed and likeness, itcauses decay and loss of constitution, whereas the similarity of offspring to the prepotent individual, if it exists, is not and cannot be recognised by reason of the similarity of the- : -ether parent. If, on the -contrary, it isused on other races it causes variationsfr Om those races to greater extent than' if prepotency had not existed. For instance, df we assume a ‘.Shorthorn herd and a polled Angus bull amongst them, the calves will be to a great’extent* of the polled Angus variety, and when these grow up, and breed in their turn, to other representatives of the original herd, the polled 1: Angus blood will/require much more wiping out than if the first/cross:of that breed had not been prepotent.. So that prepotency is ' a cause of variety in. outbreeding, and pot always a cause -of similarity in - inbreeding. c! y-fi'

Ip breeding is said by J*rofessor Ewart not to induce a’ sterility, but in some races it. unqxies.tionably: does so. '-Oroeeed animals are'more fertile than inbred ones/and, on the other hand) .hybrids are. frequently sterile. ‘ /It jseenis that violent crosses bet when varieties create reversions to the likeness of' vigorous mature ancestry ; whereas crosses ‘ between far-removed species revert further hack, and sometimes to immature . as well as remote ancestry. ‘For instance, the stripes upon Professor Ewart’s zebra and horse hybrids are not the .stripes of the sire, but those similar to the adidfe of a totally different species of zebra ; and also are more like the pure-bred! young of the father—-Burcliell’s zebra. That is, they have shadow stripes between the others, and some of these are as distinct and dark as those stripes which in them represent the distinct stripes in the pure-bred, so that they have more stripes, and smaller, ones, than their sire the zebra. Moreover, their -.seed gernis are immature, and consequently they are, or were for a period longer than horse colts would have been, sterile, and perhaps remain so) like mules.

In crossing sheep in France, it- was found that the had "breeds (by which is meant those which have not come under the influence of high feeding) were Piepotent over the better breeds, and tnat crossing was a failure. This was got • over by breeding together two diftereru ports of country breds, and so breaking clown prepotency, and when this was done the crossbred ones bred good pro'duee to the highly-bred sheep. Professor Ewart adopted: the same plan with three varieties., of tame pigeons but instead of the tnoroughbred showing his influence over the crossbred! parent, the offspring reverted from the mixture of three fancy types to the original bln© tock ancestry of all. : These are but a few instances out of multitudes which go to .show that if there is any law in breeding besides tnat of variation, its exceptions must be more : important than the .rule itself. Professor Ewart, unlike Herbert Spencer and manyq others, is not a believer in telegony. He does not believe that the influence of a, previous mate affects the offspring of a later one. English breeders are not w r ith him m that but it must be said that he has studied, the question much more systematically than they have. I mention it - to remark that if there is anything m it there is additional ground for believing that variation is the only constant . law in reproduction of species. Against this law we have it asserted that like begets like,” and we have the undoubted quality of family likeness to deal » -with.. Breeders of cattle m particular have made the most of that, and have bred from brother and sister with the best possible results. They have established families alike in- character, but not always alike in colour, and they have , done it by a good deal more inbreeding , than goes on in Nature, but the horsebreeder cannot follow their example, because his object is to increase muscular vigour, and: their practise has been to diminish it. The muscles that win decadence from the active vigour of the original wild! cattle is the delight of the breeder, increased muscular cigour is looked for in the horse with every new generation. It is admitted! that the thoroughbred! has increased Sin at the shoulder with every century. We, in our day, can see the Arab .increase 2in in a generation under the artificial con- ’ ditions which surround all horses, except ' mountain ponies, in this country. There ' ds certainly as. much difference between the thoroughbred of to-day and the Dai-

ley Arabian as there is between the Shorthorn and the European bison. But the transformation has been in different directions; one in the increased power of doing work, and the other in the increased power of feeding humanity on marbled beef. I wish to accentuate this difference, because there is some belief that, by means of inbreeding, a race of ponies having all the vigour of thoroughbreds can be maintained at one standard height. But close breeding results in loss of vigour .and loss of height, and in variation from originals, although it results also in family likeness. Crossing, on the other hand, re-

suits in vigour, increased size, and, after the fh.vt generation, in the blending in chance degrees of the two types ■crossed. In the creation of new breeds of horses the only point of advantage that can be gained by inbreeding is therefor family fineness; but in order to retain vigour we cannot have that close inbreeding that insures family likeness. It appears, therefore, that if we cannot c eate a useful prepotency by inbreeding we must wait for it it we desire family likeness and new breeds of horses. As Mr Gallon says, prepotency is a sport- itself; as Professor Ewart says, it accompanies other sports, and, con_ sequently, when a sport appears in the exact shape of what is wanted, being itself a chance variation from its breed type, that will be the animal t-o make much of for the creation of a new breed But in order to know it as a sport, with its valuable quality cf prepotency, it must be of a pure race. This is to say, if it were the result of a blend of two or more sorts it would not necessarily be a- sport ;at all. It might be the exact one-third of each of three sorts, and might reproduce any one of them, or any two, in any differences of proportion of each.

The ordinary barn-door fowls are wellknown instances of the possible variations in crossbreeding. There is every type and colour represented but there is never anything really distinctive except the reversion in colour and markings to the jungle fowl, or the black-breasted red game fowl, that is, to the original ancestral type of all the varieties, or to •what is believed to be so. The barn yard may be said to confirm Galton’s law, 'with this difference, that whereas every one of the eight of the greatgrandparents is supposed by him to have one-eighth influence on each descendant, it has no apparent influence ■whatever on seven, and an overpowering influence on the eighth. It takes an old man’s lifetime to make observations of this kind in horsebreeding, because of the length of time the horse lives and breeds, but there is nothing known about horses that in the smallest degree upsets the common knowledge gained from the poultry yard. But there is another consideration that still more involves the intricate problem before the horsebreeder, and it is that the children of the horse differ according to the age of the horse. This is generally admitted by the universal objection to breeding from aged parents, and the general idea that too much must not be expected from the firstborn of very young parents. It is not safe to accept the view that features ■and characteristics acquired in a lifetime are not inherited. In no other way ■could instinct be in the first instance transmitted. For instance, how did the habit of pointing and backing naturally first come into the breed of pointers ? That is, how did the short_p-au.se before the spring of the wild animal come to be developed; in a steady point without any ulterior object ? It may have taken many generations to get it fully developed as ,we see it, but us, long as acquired habit was transmitted to some extent, that is all that is necessary to the point under discussion. If it is admitted, and I see no way out of it, then in theory, as i n practice, the offspring vary with the age of the parent. If this is so, then age in tire individual is equivalent to several generations of young indr. iduals in stamping character, and the question arises—ls it not better to go breeding from an old animal than from his descendants ? that is, when circumstances permit, and inbreeding is no greater in one case than in the other. I have never seen the following observations or my own confirmed by those who have given attention to the matter, but I will nevertheless quote it for the sake ..of getting it confirmed. It is that half-brother and sister beget apparently more inbred offspring than full brother and sister do. I have often observed the failure of such animals as are bred to do something /when the former plan is resorted to. I look at it in this way; the produce of A and B and of A and C are mated, and the inbreeding is then entirely to A, whereas when the mating is between the produce of ,A_ and B there is a balance of inbreeding, and the influence of sire and dami are not swamped by either A or B. There is a general opinion 'that if an Arab were bred to a shire mare the produce would have the lumbering long head of the Shire and spindle skanks of the Arab;but these views are based on breeding from crossbreds on one side and not from pure breds, and that factor upsets all calculation. It would probably take several generations of bad breeding before the above results could present themselves from pure-bred animals on both sides, however different they were, because, as a rule, violent crosses clo not blend in the first generation. Off supring may follow either purebred parent or may revert. It is probable that no crossbred animals can be used to establish, a breed of polo ponies with success. It tcan only be done with similarity of results by breeding Arabs up to the height required, or by breeding thoroughbreds down to dt. Crossbreds have this great ob-jection,-that as the breeder never knows what will probably be bred, he nevei* knows how, or in what direction, to influence results. If, on the other hand, he knows what the tendency is, as in the case of the Arab, to come too small and with had shoulders, and as in the case of the thoroughbred to come too big, he knows how to set about improving the chance of what he wants to get m

each case. But he is hopelessly defeated when, having regard to the last foal of the half-bred which might have been too small, he provides the best of good living for the mare .again in foal to the .same horse, and is presented with a near relation of the shire horse for his trouble, when his aim has been a peny of thoroughbred character. The lesson of those animals which have more than one young at a birth should not be thrown away. It is seen there that exactly similar conditions preduce a great variety of results. It is, therefore, probably not external! condition which causes a half-bred mare to breed a carthorse to a thoroughbred stallion, and such extreme examples are not uncommon. The point of this is that .nothing the breeder can do -will establish uniformity of breeding from the half-bred mate’s contribution towards the offspring. The more they all follow' the prepotent sire -the less preordained variation between them will be apparent, because less will be inherited from the female side. It is. necessary to remember, after having discovered the desired prepotent “sport” stallion, that one siva!low- does not make a .summer, and that it will require a succession of such “sports” for several generations to create a new breed of horses or ponies. Polo has collected a large number of ponies all of one type, but if it w'ere attempted to breed similar animals from any two of them the results would be doubtful. And if in years to come the whole of their descendants should be blended into one family group the resists of breeding would then he less doubtful; but how many generations will xc require to obtain such a blend?— “Country Gentleman.”

Rape, Mustard, Thousand-headed Cabbage and other agricultural seeds of besfe quality from Nimmo and Blair, Dunedin.