Part 6

Part 6

  The mystery of domestication – the foundation for adaptability to man- made environments.

In part 5 we began to look at how modern methods of horse keeping evolved, and the difference between the way in which the domesticated horse is kept and the way in which its natural relation lives. But perhaps before going any further we might take a closer look at the whole process of domestication itself as it is precisely this that underlies the human equine relationship.

“Domestication = that process by which a population of animals becomes adapted to man and the captive environment by some combination of genetic changes occurring over generations and environmentally induced developmental events recurring during each generation.” (Price, 1984)

It may seem strange to talk of ‘captivity’ when referring to the horse, yet our domestication of the horse is dependent on our ability to keep horses captive to one degree or another. Clearly the massive differences in the way horses are kept make it useless to talk about captivity as if it has a fixed meaning.  It has been suggested that it is better to think of a continuum with ‘wild’ and ‘captive’ at either extreme, which we might take as suggestive of degrees of captivity. Let us say that the extreme of captivity might equate to keeping a horse head tied in a stall, in which it is not possible to turn, and in an environment in which there is no possibility for expression of natural behaviors. Even then the degree of captivity would be affected by the number of hours of exercise allowed, whether there were any free ‘turn-out’  hours, how often food were to be offered, and how natural or otherwise that food might be. Moving along the continuum towards ‘wild’ we would see management systems under which the degree of freedom of behavior increases; for example a horse alone in a fenced one hectare enclosure without shelter, through to horses kept in some kind of social group in a twenty hectare enclosure with tree cover to provide shelter from either rain or sun.

An interesting thing about this continuum is that it is also possible to replace the terms used at each extreme with other labels. Instead of ‘captive’ we could as usefully substitute ‘interests of the owner/keeper’ and at the other end ‘interests of the horse’. So, we would have the extreme of the horse kept head tied in a stall representing the interests of the owner/keeper – minimum space taken up, easiest to muck out, least effort needed to keep the horse clean (I assume in this stall scenario that the horse cannot lie down), least time taken to prepare the horse for work. The interests of the horse in this extreme are subjugated almost totally to the interests of the keeper, although there may be some variation according to exercise or ‘turn-out’ time – if allowed. At the other extreme the horse lives an unfettered existence, confined only by the size of territory and free to experience both the full natural expression of behavior and also the potentially life threatening vicissitudes and challenges of weather and environment.

At some point along our continuum a balance will be reached, between captivity and the freedom of wildness, between our interests as owners and those of the horse. Not only is this balance important to our ethical treatment of horses but also as a microcosm of our approach to the world in which we are all sustained.

It seems fair to suggest then that some understanding of the process of domestication is needed in order for us to see where we and the horse have been together, what has been brought along, what may have been left behind – and, most importantly, where we might head from here.

The first point to be made is that out of the thousands of species only mere handfuls have been successfully domesticated. This then is no common, easy task, but relies on both domesticator and domesticated to function. We generally assume that it is ourselves as domesticators that are the ‘executive’ partner in the relationship, which is to say that both the intent and actions required to fulfil that desire to domesticate came from us. But here, once again, is a notion that should be challenged. Most people would have no trouble answering the question: which animal was the first to be domesticated? Yet if we go a little further and ask was if it was man that sought to domesticate the dog – or was it the dog, as an opportunistic hunter and scavenger, that played the executive role and began to occupy the periphery of human settlements fewer people would be able to answer.  So, might it be that it was the dog that initiated man in the benefits of bi-species relationships? In the thousands of years it took for dog and man to develop the mutually beneficial strategies for hunting, guarding and waging war it could be fairly argued that the concept of domestication was itself being learnt – and that, in the dog, man had an excellent primary teacher.

Might it also have been the dog that facilitated the second domestication – that of the sheep, not as a partner but instead as the first method of securing a convenient and regular supply of meat and hide? In part domestication requires that an animal becomes de-sensitised to the presence of humans, so clearly the first requirement must be to manipulate that animal so that it stays in some degree of contact. Many present day dogs are quite adept at driving sheep towards their handler, even if totally untrained in stock work. It can be argued that this is the result of artificial selection over the millennia – but it can also be argued that this is no more than a manipulation of group hunting strategies in which the more junior pack members drive prey towards where pack elders wait.

The next animal to be domesticated was the pig. Like the dog the pig is a social animal adept at scavenging. The early middens on the edges of human habitations were undoubtedly of interest, so, like the dog, the pig presented itself for domestication – and, at one and the same time offered man a cleaner of remains and an extension to the convenience of easy meat, even if at some risk of disease. Next in line after the pig came the goat, yet another social species, and again it seems very likely that the dog could have facilitated. From this important development came the harvesting and use of milk.

If we look back over the last few paragraphs there are clearly similarities in the natural attributes of these animals that made domestication possible. Each of this first quartet are social species first and foremost, and it is this quality that is arguably most important. Al l social animals have a sense of ‘group’, ourselves included. Growing up in such a group entails the development of a variety of skills, among which is an acceptance of, and memory for, other individuals and their position in the group or status. It is this basic biological mechanism that allows there to be leaders and elders, that allows the individual to place themselves within the organisation of the group and therefore to behave appropriately – including in which is the ability to avoid inbreeding. It is merely an extension of this mechanism to identify and accept individuals of another species as ‘honorary members’ of ones own group. This then is the root of co-operation, whether between individuals of a species or across species. In fact it is becoming widely accepted in science that this is also the biological root of morality.

A closer look at the way in which this last concept might operate is well worth while. Imagine if you will, a pair of puppies rolling about in their natal den. The play is all snapping teeth and kicking legs, carried out for the most part in great good humour. As the pups grow and learn each discovers that bites should only be so hard, or else play escalates into anger and real aggression. In other words there are rules, which must be first learned and then obeyed. These rules also change according to the individual with whom the pups are interacting, so, for example, to direct the same playfulness towards an adult as a sibling is clearly not allowed. Breaking the rules generally results in unpleasantness and so is avoided, whereas compliance – co-operation – generally results in pleasant experiences or good reactions from others. Trust also becomes an important part of this equation. By this natural social process young individuals are able to learn to trust others – an essential element of the domesticator/domesticated relationship that can only be sidestepped by absolute confinement in which escape is impossible. Even then handling is made that much easier if there is trust. One might almost say that there is a biological morality implicit in the domestication relationship, if for no other reason than that of a shared behavioural paradigm. Of course this also challenges the idea that it is only humans that have morality, a commonly held, but flawed, notion.

So by the time man started the domestication of even larger and more powerful animals he had already been assisted in gaining a great deal of experience. Without this it is doubtful that domestication of either cattle or horses could have been achieved, particularly with the limited resources available to the early domesticator.

Whatever changes might later be made to the wild phenotype those first animals had to be controlled so that they could be kept in close contact before selective breeding could be used to effect any change. As with all such developments there must have been a great deal of trial and error, bruises, broken bones and failures, before the art of domesticating the horse became widespread.

First let’s briefly consider what horses were like around 6000 to 7000 years ago when domestication began. We know from genetic studies that the modern horse is derived from a number of different populations, each of which would have had some particular differences from other groups. How is it that this can be stated so categorically? Simply that the total environment in which an animal lives impacts directly on the nature and appearance of that animal via the process of natural selection. And within that total environment are different patterns of weather and extremes of temperature – which, in turn impacts on the availability of food and water, and requires greater or lesser degrees of locomotive energy to be spent in obtaining it. The differing predators, diseases, terrain and mineral content of feeds all contribute to this ‘localisation’ effect. The effect still occurs within domestication, as is testified to by the great number of breeds of dog. The introduction of a particular breed of domesticated animal into a new captive environment can typically still result in high levels of mortality within the first generation, decreasing as adaptation increases over the succeeding generations.

There is a consensus that there were most likely around four or five genetically distinct populations of horse, none of which, obviously, could have been so different that they were unable to cross-breed. Where such differences do exist, say between the horse and donkey, there are limited possibilities for reproduction. What might these differences between populations have amounted to? Length or quality of coat is an obvious, as is overall size and height. But we might also guess that density of bone, degree of reactivity, growth and durability of hoof, resistance to disease, defensive strategies, colouring, size of eye, ear and brain, and the numerous little distinctions that make one horse recognisable from another might all have been included. One thing we can be reasonably sure of and that is that sizes were smaller. Horses over 160 cm would have been unusual, with pony size heights the rule, between say 140 and 150 cm. 

Let’s now move on to consider what the effects of domestication were on the horse. Some general rules can be applied, one of which is that domesticated individuals have smaller brain-case sizes than their wild counterparts. It might be supposed that this is the effect of being relieved of the necessity to order their own lives. Brain power is certainly very costly in terms of energy, coming at a higher price than the maintenance of other organs, so it might be expected that it would reduce under the less trying domesticated environment where predation might be extremely limited and where instead of having to search for all feed a good amount might be provided. More specifically it is arguable that the parts of the brain required for executive function might become attenuated. Whether brain case size increases in feral populations over time remains to be seen, it may be that feral populations have not existed for a sufficient amount of time in which the reversal might occur. It may also be that feral populations are not now exposed to the same degrees of predation or natural danger as their distant ancestors, and so will never require as large a cognitive area of the brain in order to survive. Equally there is some recent evidence to suggest that brain development is increased in those individual animals that occupy positions of high social status.

Al though the same evolutionary processes that produced changes in phenotype over the millennia of the horse’s existence as a wild animal continue to operate under domestication, the speed with which these changes can be made to occur is far greater. This quantitative difference is accompanied by a qualitative partner. For changes to become fixed in the wild there must be a clear benefit in terms of overall survival fitness, which must then persist for some length of time before the change can become widespread throughout the population. This is not the case under the conditions of artificial selection that operate in the domesticated state. Phenotypic changes that confer no benefit to the animal can be made to spread by selective breeding for a particular trait. In fact there are going to be changes in phenotype that actually produce an individual that would be far less likely to survive under wild conditions. A good example of this is size. Large domestic horse breeds that rely on concentrate feeds to maintain muscle bulk and the energy to motivate such a large mass would be unlikely to survive were they to be left to become feral on land that produced only medium or low grade herbage, or where extensive movement might be required in order to find sufficient quantities if feed. It is vitally important that we be aware of the changes we make to phenotype, since the ability to breed or socialise effectively can also be adversely impacted such that we produce animals that are not able to fulfil the basic functions of a living creature without our interference. And if this sounds as if it might be an ethical issue, then so indeed it should.

Neither should it be thought that domestication removes the pressure of natural selection. Those animals that fail to survive the transition from the wild to captive state, or from one captive environment to another do so under the same mechanism that affected their wild ancestors during transitions from one wild habitat to another, or during environmental changes within the same habitat, say of climate or food species.

Some horse enthusiasts will no doubt surmise that the years of breeding in domestication will have also altered the more important behavioural traits, and argue that the modern horse surely has not retained the same behaviors as its wild ancestors. This is not a safe assumption. There is sufficient evidence to suggest that the most important survival behaviors, such as those governing mating, maternity and predator avoidance may well be more resistant to change than other traits. To complicate things even more it is quite easy to confuse the impact of an environment in which the development of certain behaviors are either unsupported or expression made impossible with the absence of those behaviors.

We are all aware of the concept of the child prodigy, in which, for example, early exposure to a musical instrument produces a virtuoso by the age of ten. It would be quite reasonable to conclude that there must have been some latent ability in the child in order for this exposure to have effect, equally, and with far greater certainty, we can assume that had there been no external stimuli in the form of the musical instrument there could have been no prodigy. Would the absence of a musical instrument have altered the latent ability in the child? No, it would merely have removed the opportunity to find expression for it. Al though it may well be that had the instrument been offered some years later the latency may have become engaged in another area, or have been lost. This type of scenario is not confined to human prodigies or to musical skills, there are a great number of time-coded behaviors that require triggering within a specific time frame in order to find expression. These are particularly important in social species, and operate within the arena of social, sexual, and maternal behavior. It is here that domestication may have a very significant impact.

The degree to which the captive environment promotes or denies expression of such important learning periods, whether closely time-coded or not, is directly related to the position that a specific captive environment occupies on our original continuum. And not only is it possible for such an environment to be contrary to the best interests of the animal concerned it may, in both the short and long term, be contrary to the interests of the keeper.

As an example let’s look at just one element – that of maternal behavior. It is very common management to isolate pregnant females of various species, dogs, pigs and horses being but three. The intent behind this may well be quite reasonable; a desire to protect the animal during a time of greatest vulnerability and to hold the animal confined in a place to which there is good access in the event of the need for human assistance. But it is also prevents any expression of group behaviors associated with birth that may be common to that species. Of course if it is possible for the mother and progeny to be reintroduced to her social group once birth is over then the disruption to the natural behavioral paradigm is reduced. In many cases what will happen is that there will be little or no possibility for expression of these behaviors. In the case of the horse the mare, kept in a nice warm stable with CCT system, is not allowed the support and protection of other mares, of her older progeny or of her stallion. Instead of the foal being induced into equine society by receiving the visits of the other herd members, firstly of those closest to her mother, followed by those having either less connection or status, it remains in isolation. And, in turn, when the mare foals again, the yearling will have been removed so that it can neither give support or run interference, nor experience at close hand the paradigm of birth so that, later on, whether it is a colt or a filly, it too will know what to do.  It is also typical for stallions and mares to be kept separately, given access only for short copulatory events under intrusive and restrictive handling. The captive environment allows neither the observation of courtship behavior by offspring so that they, in turn, may practise such behavior, nor does it provide any free expression of this most important of all behaviors to either the mare or stallion.

The most cursory observation of social species suggests that the companionship of others of the same species is the source of great comfort and is essential to psychological wellbeing. This too is an essential survival function. It is the lack of companionship, loneliness if you will, that drives an animal to join with, become part of, and remain with a group such that both the individual’s and the group’s ‘fitness’ is enhanced. This is surely one of those ‘core behaviors’ that are so central to survival and resistant to change by artificial selection. The captive environments typically associated with the keeping of horses very often include the imposition of either solitary or near solitary confinement. Yet we have established that it is most unlikely that artificial selection during the domestication process of the last 6000 years will have altered the animal’s requirement for the society of others. Here too we can clearly see natural selection taking effect. How many stallions, kept in isolation, become so dangerously and aggressively maladjusted that they are either euthanized or subject to life threatening injury? I would very much like to be able to quote a number, but the truth is that neither I, nor as far as I am aware anyone else, has any real idea. Yes we know it happens, and that it is not confined to the poorer captive establishments but that it is liable to occur in any situation where a stallion is unable to adapt to such an extreme captive environment.

Another of the commonly held beliefs is that genetic diversity declines under domestication. This too is unreliable. Comparisons between wild and domestic populations show that diversity is most often greater in the domesticated animals. Once again it is canines that offer an easy example. The wolf varies remarkably little across the terrain to which it is indigenous, a little variation in size and colour, but nothing as marked as the difference between say a miniature poodle and a Great Dane! Yet all are the same species, and can interbreed freely to produce fully viable offspring. The reasoning behind this is simply that the wolf possesses those traits that lend it the greatest degree of overall survival fitness possible in the wild environment. Diversity, for example, as might be represented by changes of coat colour that would interfere with the wolf’s ability to blend in to the background could not survive natural selection, whereas a domestic dog coloured bright red is immune from such pressure by virtue of not having to feed itself. In the same way it is reasonable to suggest that the cross-breeding of the original four or more populations of horse has been far greater under domestication than ever it would have been had they each remained in their specific wild environments. There are few countries or regions in the world that do not now have some particular type of horse – more usually several, ranging in size or build and, of course, uses. While this does indeed represent a great genetic variability the similarities are equally striking, as are descriptions of the virtues of breeds given over to similar uses.

It is worth remarking also on the similarity of paraverbal or body language amongst the various breeds of horse - no need for dictionaries or translators here! An amusing anecdote on the subject springs to mind. It has always been part of my handling style to talk to horses in my care, the basis being that while the horse may not understand my words they serve to trigger the associated body language in me, which horses are so adept at reading. When only recently in Spain , where my wife and I ran a large trekking stables, a number of Spaniards asked me how it was that the horses, all of which had been purchased locally, had learnt to understand English so quickly. It would seem that neither artificial selection nor the associated genetic variation have produced any major difference in the communicative behavior of the horse. Of course we could merely assume from this that body language is fixed by body design, although this is certainly not supported by the regional or cultural differences in human gesture. Or we might also conclude that the basics of such paraverbal communication are one of those core-behaviors that are most resistant to change. No doubt there is much more that could be said one both sides, and perhaps the safest course is to accept that both options contribute to some degree.

In part 7 we’ll conclude our exploration of domestication with what is arguably the single most important issue – that of tameness.

© Andy Beck – W.H.E.E.P. 2004

 Part 7