Dr. Hans J. Jacobs held a reading on population genetics during the ISF meeting of 21 November 2009 in Asperen (The Netherlands).
Population genetics or: A White Rhinoceros with outstanding characteristics
To begin with I am not going to treat you to a full-fledged scientific paper on population genetics.
I would like – not without provocation – to direct your attention to something we are obliged to ponder on. Most of you are probably familiar with the main features I am going to address. But many people (including breeders) who are aware of these contexts still seem to think one needn’t worry about them yet. I sincerely warn against this attitude! We have to start thinking now: the consequences are inevitable in the long run.
Please let me guide you through 8 general steps in population genetics.
1. To begin with a comparison: a modern breed of dogs correlates with an extended family with closely related members. Do I have to hint at the deficiencies of certain royal families like the Habsburgs, etc.? A genetically highly diverse organism can be compared to a jungle and a pure-bred population to a monoculture.
2. A few brief remarks about evolution: In the animal world the sole purpose of sexuality is to guarantee as much diversity with as many genetic types as possible. The combination of two half chromosome sets constantly produces new prototypes which have to stand the test of time (they will soon be extinguished or they prevail). The choice of sexual partner, as we all know, is basically a qualitative selection and serves the one and only aim of evolution: survival of the fittest!
3. A small detour: I would like to contemplate on the difference between breeding domestic animals in comparison to conservation breeding in zoos of which sole aim is the survival of a species. To guarantee their survival, genetic analyses are conducted to detect genetically preferable combinations. The aim is an as high as possible genetic diversity. Nature itself achieves this principle of evolution by migration or expulsion of male offspring from the pack. Populations beneath a certain level of diversity (for instance local forms, insular populations, etc.) possibly cannot be saved.
4. To come back to the breeding of any purebred animal – all natural criteria are shifted by the interference of man: sexual partners are selected on the basis of desirable parameters that are often no longer connected to performance (for instance hunting, herding, guarding, etc.), which was the basic quality of the dog. Unfortunately “performance” now also includes beauty, a most human and by no means “healthy” criterion. In the first case selection for breeding was based on a clear purpose and led to the rejection of undesirable or inadequate qualities. In the case of beauty, selection has nothing to do with “Nature” any more – it follows human paradigms (for instance childlike characteristics).
5. The previous considerations lead to the central topic: genetic impoverishment! Every breed stems from only a few specimens to start with. And in the course of its history every breed loses more and more of its genetic diversity. This process – and I ask you to be well aware of this – is inevitable!
Pure breeding is always linked to certain features that are generally described in the breed standard. Other features and qualities are lost because they do not meet with man’s taste. This process is indisputably combined with genetic loss.
The stricter “humane” selection takes place the faster this genetic impoverishment occurs. For example: if all colours but one are eliminated, one can imagine what happens genetically. Not only are other colours lost but all the other genetic components that were included in these combinations. At the same time the risk of genetic diseases increases dramatically. The high number of genetic diseases is in principle nothing but the result of genetic impoverishment.
I would like to sum this up in an abstract, theoretical way: homozygosis aims at the heredity of desired dispositions and leads inevitably to the loss of genes. Heterozygosis (the inherent principle of nature) aims at the highest possible variance of genes.
6. After these abstract considerations let me become more concrete.
What are the consequences of “natural breeding” and “humane breeding”? Heterozygosis guarantees vitality, fertility. This includes health in general, an intact immune system, physical and mental abilities, etc.; everything else is eradicated.
Aim and purpose of homozygosis are specific features. As soon as “beauty” (big round eyes, a shortened jaw, etc.) becomes the main desirable aspect, genetic health is in danger! A standard (and its interpretation) that gives a strict description of the ideal type of a breed, can lead to the narrowing down of the breed. Beware of striving to over-fulfil the standard in itself or in singular aspects! Amendment of the breed in the sense of champion breeding is more than questionable. It misconceives what is lost genetically in reaching phenotypical refinement.
Experiences in other breeds account for loss of vitality (longevity), more proneness to diseases (deficient immune system), fertility problems (irregular heat, small litters, loss of the ability to mate), or dogs developing a difficult character (aggressive or shy).
I would like to squeeze in a brief paragraph here, which is certainly not meant to calm you. Until now there are only few serious problems in our breed. But they are inevitable! Perhaps the first danger signals are already being detected – we must address these. If we wait until the danger signals are undeniable it might be too late!
Please do not expect me to close my considerations with an efficient recipe. However, the complexity of this topic must not lead to resigned inactivity. Let me pick out one aspect only: today in all breeds we see male dogs being used for mating more than a dozen times (to leave aside their sons and grandsons). Many others are not used at all (too often the only reason being “beauty” instead of genetics). Very often these breeding dogs are considered to be “good hereditary donors” – as a matter of fact this generally only refers to the beautiful appearance promising good show results. Biologically these “good hereditary donors” are “gene-losers” since they cause genetic degeneration because variation is lost. A champion is in genetic terms an absolute problem!
Before owners of champion dogs get over-excited and reach for their gun to kill me: the same is true for bitches!
7. I would like to close with e few keywords which refer to possibly conceivable methods. In my eyes our top priority is to make everybody on all levels in all organisations in all countries aware of this very complex problem. It goes without saying that this must happen with the international situation in mind. The reasonability of national regulations fades in times of globalisation. If you want to change something effectively you can only do so on an international level without national interests at the back of your mind.
– The number of times one male dog mates must be –internationally – limited so that in terms of variance other dogs are used as well. Whether to accomplish this aim national breeding committees are still suitable or whether a breeding committee on an international level is needed I leave trustingly to your discretion!
– The inbreeding coefficient needs to be given much higher relevance. Maybe it should be included as an integral part of the pedigree. Our national breeding committees should inform us about the relevance they allot to this coefficient. Does it come first?
– As far as I can see we should do everything in our power to prevent “fashion breeding” by which I understand focussing on show results as the major breeding aim. We do not need any plush monsters but a rustic Schapendoes. I am aware that this point is especially difficult to accomplish. At many shows one can see Schapendoes being combed and brushed even at the ringside. Possibly a new interpretation of the standard is needed that underlines the natural appearance of our breed and will prevent the Schapendoes becoming that “stainless steel table-knife” Toepoel warned against.
8. Of course it is legitimate to rejoice about good show results (I certainly hope to). And of course shows are major events in the entire context of breeding. But I dare to question what has the higher value when the health of our breed is concerned. And of course it will be very difficult for many breeders (myself included) to change perspectives and to view “breeding” in a new light.
In zoos nobody tries to breed white rhinos with outstanding characteristics. The aim is to amend the frivolous damage which man has inflicted, and still inflicts, by genetic management to save a species from extinction.
We should not bask in today’s situation however positive it might seem for our breed. We should contemplate this context with a view to the future and we should prepare ourselves with a sense of proportion and with prudence – but certainly without hysterics – for problems that will definitively come knocking at our door.
Dr. Hans J. Jacobs