Exogamy & the Horse

There is a strong cultural taboo that forbids closely related people producing children together - genetic proximity. 

We may make bad jokes about rural areas and first cousins, but we take incest seriously enough to legislate lengthy jail sentences for those who break the rules, and so indeed we should, as the outcomes can be quite serious.

We tend to apply the same restrictions in breeding domestic animals, and for exactly the same reasons - namely that excessive genetic proximity can produce biologically or psychologically (or both) non-viable progeny.

In animal breeding we are prepared to take a certain amount of risk in order to attempt to 'fix' characteristics that we particularly wish to select for. The examples are fairly obvious:- milk production in dairy cattle, high percentages of lean meat in carcass animals such as beef and sheep, and so on. Whether or not we, as individuals, might agree with this practice, there are clear reasons. Better, or cheaper, food production with which to feed an increasing population, higher returns to farmers and producers, less waste and so on.

A practice that has less reason behind it and yet is carried out none the less is that of breeding animals with purely aesthetic considerations in mind - whether this might be for size, color, conformation, length of hair, leg or snout.

The practice has created some problems in various species in the past, and will most likely do so again in the future.

The most common species for this type of treatment is the domestic dog, which, as a reasonably rapidly maturing species, can be strongly influenced over a relatively short number of years. Selective breeding for size and appearance has produced accompanying problems such as hip-displacia in German Shepherds, short life expectancy and proneness to cancer in Great Danes, respiratory problems in Bulldogs to mention but a few of the most obvious. But there is also an unestimated number of canines that tend toward extremes of nervousness and hysterical behavior, many of which may also have learning dysfunctions. Of course the question arises whether these are merely symptoms of bad management on the part of their human handlers, rather than innate behaviors.

Quite clearly then, even though we may be willing to indulge in a degree of trial and error in species where we are able to euthanase without censure, we are aware of the risks involved in allowing too high a level of genetic proximity or, to give it a more mathematical name, coefficient of inbreeding.

Have we come by this knowledge simply through trial and error, with all that implies, or are we to some extent 'hard-wired' not to look to immediate family for procreative partners? And, if we are hard wired, why are so many human males apparently prepared to go against such basic conditioning? The question of bad management can not be overlooked as a reason, as with canines. Generally we seem happier to blame a 'poor' environment than to really bring it home by suggesting that our own self-management, as a species, is actually not very good.

Let us explore the hypothesis that we have an innate 'taboo' against inbreeding. We could justify this quite simply, if we wished, by suggesting that it would be efficient in an evolutionary sense and would then be likely to be selected for in the general population over time. Certainly if inbreeding produces, as we know it does, weaker, less viable, individuals than outbreeding then why should the progeny of the 'outbreeders' not come to dominate? More to the point, inbreeding in small populations could easily become very dangerous so that the viability of the group was terminally compromised. The tendency toward this 'inbreeding' behavioral paradigm could be expected to decline rapidly.

We do not have to look too far back in time to arrive at a point where it was the consensus that only humans and, (grudgingly), perhaps primates, were able to distinguish close family from the general population. We now have evidence that other species, most particularly those that live communally in 'towns' such as Meerkats, are able to recognise close relatives and therefore avoid breed with them.  Such is the potential threat posed by inbreeding that it must surely be likely that many species have evolved to possess an innate behavioral paradigm which is broadly preventative of inbreeding.  Why should we not expect the Horse, also, to display this innate behaviour?

To refute this in equines, one would have to suggest some way in which exogamous behaviour would not be efficient, and would not confer any advantage. Surely that would not be easy - an inbred weakling would not survive long. In a precocious prey species such as the horse a foal needs to be as strong as possible, as quickly as possible, if it is to avoid becoming a predatory menu item long before reproductive age is attained, which in the wild we might take to be four years of age.  Four years in which survival fitness must be repeatedly demonstrated!

We have then every reason to conclude that exogomatic social structures might be present within the framework of naturally occurring Horse behavior. Yet very little work has been done on the subject. One might postulate that we have been side-tracked away from looking at this in greater depth by our assumptions regarding morality - that inbreeding or (our special word for inbreeding in the human species) incest is immoral and wrong rather than a poor survival trait.

The equine industry, internationally, is facing an increase in reproductive problems. Low fertility, poor conception rates, decrease in apparent maternal instinct, congenital defects, abnormal conformation and so on. Some of these would seem to be due to selection criteria that have little to do with survival fitness in any natural sense but much to do with short-term commercial or aesthetic values.

If the incidence of these problems continues to rise, the industry will bear a burden of cost that could well impact very seriously on the 'survival fitness' of individual businesses. Is it not time for exogamy in the domestic horse to be rigorously explored?

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