The domestication of animals started around 12,000 years ago in the Near East region. This “endless process” is characterized by the gradual accumulation of changes that progressively marked the genetic, phenotypic and physiological differences between wild and domesticated species. The main distinctive phenotypic characteristics are not all directly attributable to the human-mediated selection of more productive traits. In the last decades, two main hypotheses have been proposed to clarify the emergence of such a set of phenotypic traits across a variety of domestic species. The first hypothesis relates the phenotype of the domesticated species to an altered thyroid hormone-based signaling, whereas the second one relates it to changes in the neural crest cells induced by selection of animals for tameness. These two hypotheses are not necessarily mutually exclusive since they may have contributed differently to the process over time and space. The adaptation model induced by domestication can be adopted to clarify some aspects (that are still controversial and debated) of the long-term evolutionary process leading from the wild Neolithic mouflon to the current domestic sheep. Indeed, sheep are among the earliest animals to have been domesticated by humans, around 12,000 years ago, and since then, they have represented a crucial resource in human history. The aim of this review is to shed light on the molecular mechanisms and the specific genomic variants that underlie the phenotypic variability between sheep and mouflon. In this regard, we carried out a critical review of the most recent studies on the molecular mechanisms that are most accredited to be responsible for coat color and phenotype, tail size and presence of horns. We also highlight that, in such a complicate context, sheep/mouflon hybrids represent a powerful and innovative model for studying the mechanism by which the phenotypic traits related to the phenotypic responses to domestication are inherited. Knowledge of these mechanisms could have a significant impact on the selection of more productive breeds. In fact, as in a journey back in time of animal domestication, the genetic traits of today’s domestic species are being progressively and deliberately shaped according to human needs, in a direction opposite to that followed during domestication.

中文翻译：

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从野生欧洲盘羊到家养羊的表型转变


大约 12,000 年前，近东地区开始驯化动物。这种“无尽的过程”的特点是变化的逐渐积累，逐渐标志着野生物种和驯化物种之间的遗传、表型和生理差异。主要的独特表型特征并不全部直接归因于人类介导的对更高产性状的选择。在过去的几十年中，人们提出了两个主要假设来阐明各种家养物种中此类表型特征的出现。第一个假设将驯化物种的表型与基于甲状腺激素的信号传导的改变联系起来，而第二个假设将其与因驯服动物而选择引起的神经嵴细胞的变化联系起来。这两种假设不一定是相互排斥的，因为它们可能随着时间和空间的变化对这一过程做出不同的贡献。驯化诱导的适应模型可以用来澄清从新石器时代野生盘羊到现在家养羊的长期进化过程的某些方面（仍然存在争议和争论）。事实上，羊是人类最早驯化的动物之一，大约在 12,000 年前，从那时起，它们就代表了人类历史上的重要资源。本综述的目的是阐明绵羊和欧洲盘羊之间表型变异的分子机制和特定基因组变异。在这方面，我们对最被认为与毛色和表型、尾巴大小和角的存在有关的分子机制的最新研究进行了严格的审查。 我们还强调，在如此复杂的背景下，绵羊/欧洲盘羊杂交代表了一种强大的创新模型，用于研究与驯化表型反应相关的表型性状的遗传机制。了解这些机制可能会对选择更高产的品种产生重大影响。事实上，就像回到动物驯化时代一样，今天的驯化物种的遗传特征正在根据人类的需要逐步、刻意地塑造，其方向与驯化期间的相反。