Accepted_test

The mechanisms behind the domestication syndrome (DS) have already been well explained. Starting with the pioneering studies on domestication by Belyaev, which showed that selection for tameness (impaired stress response, changes in the ‘hypothalamic-pituitary-adrenal system', HPA-axis) leads to destabilisation of the regulatory systems controlling morphological and behavioural development, resulting in the changes characteristic of DS. Later, it was suggested that changes in the activity rhythm of the thyroid gland lead to heterochronic changes (e.g. paedomorphism). Finally it was proposed that the phenotypic components of DS are derivatives of neural crest cells (NCC). Recently, the parasite-mediated domestication hypothesis (PMD) was proposed. Since parasites influence all the major mechanisms underlying DS, PMD suggests their important role in the domestication process, both directly through the manipulation of host behavioural traits and indirectly via genes related to resistance/tolerance to parasites, the role of miRNA in the process of epigenetic inheritance or the epigenetic/transgenerational inheritance of stress pathology. PMD can be tested either experimentally or comparatively. We have tested PMD here using a systematic comparative approach by analysing the parasite load in wild boar and free-ranging (grazing) domestic pigs from a comparable environment. We hypothesised that the parasite load in the domestic pig population would be higher than in the wild population. According to our preliminary results, there is evidence in favour of PMD. However, we cannot draw a definitive conclusion as there are many aspects that can mislead the interpretation. Comparative studies should be supported by a more focussed methodology, including an experimental approach.