The Process of Animal Domestication

Marcelo Sánchez-Villagra

• Editorial: Princeton University Press
• Año: 2022
• ISBN:
  9780691217680
• Categoría: Ciencias biológicas
• Categoría: Evolución

The first modern scholarly synthesis of animal domestication Across the globe and at different times in the past millennia, the evolutionary history of domesticated animals has been greatly affected by the myriad, complex, and diverse interactions humans have had with the animals closest to them. The Process of Animal Domestication presents a broad synthesis of this subject, from the rich biology behind the initial stages of domestication to how the creation of breeds reflects cultural and societal transformations that have impacted the biosphere.Marcelo Sánchez-Villagra draws from a wide range of fields, including evolutionary biology, zooarchaeology, ethnology, genetics, developmental biology, and evolutionary morphology to provide a fresh perspective to this classic topic. Relying on various conceptual and technical tools, he examines the natural history of phenotypes and their developmental origins. He presents case studies involving mammals, birds, fish, and insect species, and he highlights the importance of domestication for the comprehension of evolution, anatomy, ontogeny, and dozens of fundamental biological processes.Bringing together the most current developments, The Process of Animal Domestication will interest a wide range of readers, from evolutionary biologists, developmental biologists, and geneticists to anthropologists and archaeologists.

CHAPTER 1

Pathways in time and space

Animal domestication encompasses many kinds of interactions between humans and other species. It is a continuum of stages of a gradually intensifying relationship. This relationship ranges from anthropophily to commensalism, from control in the wild to control of captive animals, from extensive to intensive breeding, and in some cases it extends to owning of pets (e.g., Vigne 2011, Zeder 2012a, b; Larson and Fuller 2014). A fundamental and primary aspect of domesticated animals is their tameness, meaning that they tolerate and are unafraid of human presence and handling. The genetics and the physiological and morphological correlates of tameness have thus been a central focus of studies of domestication. However, tameness alone does not imply domestication, as exemplified by tamed elephants living in close association with humans. Keeping an animal as a pet does not make it domestic. Examples from the Amazon region abound. Changes in reproduction can be seen at the core of domestication (Vigne 2011).

Domestic animals emerged from small groups of individuals of their respective wild form that became increasingly reproductively isolated from the stem forms as a result of the influence of humans. They adapted to the peculiar ecological conditions imposed by an anthropogenic environment and in some cases developed considerable population sizes. Domesticated animals are subject to environmental conditions and selective pressures different from those faced by their wild counterparts. Furthermore, the conditions to which populations of domestic animals are exposed vary greatly (e.g, culling patterns, availability of food, protection from predators). Altered natural selection and continual targeted and non-targeted selection by humans led to divergence from the wild norm in morphology, physiology, and behavior. Domestic animals are increasingly used for economic and leisure purposes in diverse ways. The variety of perspectives by which to characterize domestication (e.g., symbiotic interactions: Budiansky 1992; resulting domesticated phenotype: Price 1984; Kohane and Parsons 1988) make a unique and universal definition a challenging and unrealistic goal (Ladizinky 1998; Balasse et al. 2018).

Traditionally, domestication has been defined and conceptualized from the human perspective, with our species as the domesticator. This view is no longer universally accepted, and in fact different perspectives have contributed to this change. A new look at naturalistic observations demonstrates the active role played by animals in approaching humans and in looking for benefits resulting from human proximity and interaction. It is thus relevant to examine the reciprocal impact of animals in shaping the trajectory of human biological and cultural evolution (Zeder 2017). Animal-human interactions have been discussed in terms of niche construction, a subject often treated in discussions of an expanded evolutionary synthesis (Smith 2011a; Zeder 2018). Niche construction refers to the evolutionary impact of ecosystem engineering activities that create new or modify existing selection pressures acting on present and future generations (Odling-Smee et al. 2003). Humans have been characterized as the ultimate niche constructors, and cultural niche construction has been discussed in the context of the initial phase of domestication (Smith 2011b). Domestic animals are also niche constructors. Independent of the discussion around the repetitive nature of the subject of niche construction in the literature (Gupta et al. 2017), its relevance to conceptualizing and describing ecological interactions is uncontested.

Another perspective that questions the traditional and human-centered conceptualization of domestication (e.g., Zeuner 1963) is a philosophical/sociological one. People tend to create narratives (Diogo 2017), and we have done so with domestication, in which we present ourselves as central and the makers of destinies of organisms. This notion ignores the active role of the “domesticated” and is a traditional Western European view of our place in nature that is not universal among humans (Ingold 2000; Descola 2013; Figure 1.1). The argument has been made for abandoning the notion of domestication in favor of a continuum of human-nonhuman animal relationships (Russell 2002). Although there is merit in this idea, it does not solve the issue of defining the complex phenomenon we call domestication. It is more productive to discuss the pathways to domestication and the different kinds of interactions entailed by domestication. These reflections should not obviate the recorded cases in which humans have played and directed a one-sided role in domestication, as in the case of canaries native to the Canary Islands brought to Europe and domesticated simply because of their singing (Birkhead 2003).

When the focus is on intense, selective breeding and animal management, the conceptualization of domestication leads to a view in which humans are the sole agents (Fig. 1.1, “Ego”). This view also sees domestication as an intentional and goal-oriented interaction. An alternative view arises if one concentrates on the first steps of the domestication continuum. At this point, people did not have long-term domestication plans, and interactions between humans and other animals were voluntary on both sides; therefore, from this perspective, the agent is not as obvious. The argument has been made that, based on some parameters, some domesticated animals and plants have benefited more from the interaction than humans themselves (Budiansky 1992). The increased distribution and multiplication of species that became domesticated contrast with the many challenges and disadvantages faced by humans following the Neolithic transition. The idea of human demise following the Neolithic transition has an element of retro-romantic thinking. What is needed is a multivariate evaluation and quantification of human prosperity across time, so that a nuanced evaluation of how human life has changed can be attained. Surely the result will show nonlinear changes, geographic variation, and a lack of universals.

Fig 1.1. Ego, Eco, and Evo views of the human-animal interactions. Only domesticated animals are shown.

Fig 1.2. Comparison of domestication sensu stricto versus artificial selection and other kinds of selection regimes. The geometric shapes represent the relative magnitude of variables shown along the top of the figure. Ne is the effective population size. The historical population size influences the amount of variation present in the population.

It is fundamental to differentiate the intense “artificial selection” typical of the creation and preservation of breeds (“intensive breeding”) from the domestication pathways described below, associated with the initial phase of interaction, in which a dependence of the domesticated form on humans has not yet been established. Mutagenesis screens, experimental evolution, artificial selection, domestication, and selection within species differ in important parameters in space and time (Stern 2011; Figure 1.2). A mutagenesis or genetic screen is an experimental approach used in research to generate a mutated population to identify and select for individuals with a specific target phenotype, providing information on gene function. The difference between domestication sensu stricto versus selection for “improvement” traits or artificial selection, as well as with other kinds of evolutionary and human-induced phenomena, becomes evident when comparing degree of selection and population sizes.

Fig 1.3. Pathways to domestication. Changes in intensity of the human-animal relationship are indicated.

There are different pathways to domestication. Likewise, the kinds of interactions at the other end of the domestication continuum (Figure 1.3) are not all the same. Selective breeding, aimed at preserving specific breeds or features, is different from management, which involves manipulation of growth conditions, or the environment that sustains it. The aim of management is to increase the relative abundance and predictability of a population and to reduce the time and energy required to harvest it (Zeder 2015).

Pathways to domestication

Traditionally, domestication has been seen as resulting from goal-driven human action, with narratives about selection for traits that differentiated wild and domestic forms. In reality, domestication of different species has involved different kinds of interactions. Zeder (2012a, b) formally recognized and described three separate pathways followed by animals into a domesticated relationship with humans: a commensal pathway, a prey pathway, and a direct pathway (Figure 1.3).

There is usually no intentionality in the commensal pathway, which involves a coevolutionary process in which a population uses a novel niche that includes another species. That niche could involve human food waste or refuge, which is then taken advantage of by a subset of individuals of another animal species (e.g., wolves) that were less aggressive (i.e., tamer) than the rest. In the absence of human instigation, an interaction could arise, and only later would the human-directed selection that we associate with modern domestic populations have been possible.

The prey pathway involved a human intention to increase the efficiency of resource management. Medium to large herbivores were targeted as prey, including perhaps the case of horses. Although not originally planned as such, domestication resulted from humans altering their hunting strategies toward herd management, eventually leading to control over the animals’ diet and reproduction (Zeder 2012a, b). The prey pathway probably took place in human communities that cultivated plants and did not lead a hunter-gatherer life. The directed pathway involved the deliberate use of a species and its incorporation into human life for uses such ...