The History and Consequences of Domestication of the Horse
Domestication concerns adaptation, which is usually a captive environment and which is achieved by some combination of genetic changes occurring over generations, as well as by environmentally induced changes in development that recur during each generation (Price, 1984). The domestication of the horse has profoundly affected the course of civilization. Horses provided meat, milk, and enhanced transportation and warfare (Vila et al. , 2001).
Horse remains become increasingly common in archaeological sites of the Eurasian grassland steppe dating from about 6000 years ago, suggesting the time and place of their first domestication (Clutton-Brock 1987). Two hypotheses for the origin of the domestic horse from wild populations can be formulated. Firstly, that the domestic horse was developed through selective breeding of a limited wild stock from a few foci of domestication. Thereafter, domestic horses would have been distributed to other regions (Levine, 2005).
Another alternative could be that domestication involved a large number of founders recruited over an extended time period from throughout the extensive Eurasian range of the horse. In this multiple origins scenario, horses may have been independently captured from diverse wild populations and then increasingly bred in captivity as wild numbers dwindled (Vila et al, 2001). Consequently, early domestic horses may not represent a stock highly modified by selective breeding.
Domestication involves both culture and biology. The cultural process begins where there were loose ties with the social medium of man, where interbreeding with wild forms was common and kept the horse closely related to its wild ancestor from a morphological point of view (Zeuner, 1963). The biological process resembles evolution and begins when a small number of parent animals are separated from the wild species and are habituated to humans (Clutton-brook, 1992).
These animals form a founder group, which is changed over successive generations, in response to natural selection under the new regime imposed by human community and its environment, and also by artificial selection for economic and cultural reasons (Zeuner, 1963). A review of equine genetic data has shown evidence of high MtDNA diversity of extant and ancient horses which suggests a high number of mares were domesticated. On the other hand, all domestic horses showed to have a single haplotype; interestingly even a small population of Prezewalski’s wild horses showed two different haplotypes.
It seems an extreme male population bottleneck occurred due to domestication, while reduction in the female population was only moderate (Kavar and Dovc, 2008). It could be suggested that domestication only began when the appropriate stallion was found or obtained by selection. During the further process of domestication, mares were preferentially crossed to stallions having more desirable characteristics (Lau et al. , 2009). Therefore, it has been assumed that mares from different regions varied in morphology due to adaptation to their local environment conditions.
This could explain rapid differentiation into various phenotypes during the early phase of domestication (Lindgren et al. 2004) As a consequence of domestication, housed horses often perform bizarre behaviours such as weaving, box walking, wind sucking, crib-biting, pawing, door-kicking and head-nodding (Mills and McDonnell, 2005). These behaviours, also known as vices, are considered abnormal when they occur without any primary function and might be detrimental to the health or performance of the animal (Mason, 1991).
It has been shown that these behaviours are a possible cause for gastric ulceration (Nicol et al. , 2002) and for tooth wear, weight loss, and weak condition (McBride and Long, 2001). It has also been shown that using the horse for riding has caused vertebrae problems if the rider uses incorrect posture (Lesimple et al. , 2010). There is little evidence of how horses were managed within the first years of domestication (Dierendonc). However, in most horse husbandry systems today horses are kept confined and solitary with very little social contact.
This can be seen as optimal to ensure physical health, to prevent injury or to allow exact individual monitoring (Dierendonc, 2006). However, these systems often ignore the basic needs of the horse, e. g. social contact, foraging and locomotion needs, often resulting in abnormal behaviours. The start of stereotypic behaviour usually is related to chronic stress due to mal-adaptations to cope with the environment (Hausberger et al. , 2009). Negative experiences linked to training may add to the effects of management style and lead to chronic states where the horse switch off, becoming nresponsive and apathetic (Hausberger et al. , 2009). Interestingly, although time spent performing stereotypies increases with time spent in a stall, it may also increase with time spent working (Christie et al. , 2006). While the horse has benefited from some aspects of domestication, for example the provision of food, shelter, protection from predators and care during illness and injury, many of the constraints imposed on the domestic horses conflict with their evolutionary adaptive behaviour (Waran, 2002).
When horse domestication began 6000 years ago, humans took horses from environments in which they had evolved, and were maintained as food sources within their natural environment. However as the role of the horse in human culture changed and diversified, the constraints of domestication began to restrict many aspects of horse behaviour. Today we restrict horses freedom to roam and their freedom to choose food, shelter and social companions (Goodwin, 2007). In addition, an individual horse’s reproductive fitness is largely determined by man rather than its own behavioural strategies (Cooper and Albentosa, 2005).