Mitochondrial Genome: Clues about the Evolution of Extant Equids and Genomic Diversity of Horse Breeds

A ‘long-fuse domestication’ of the horse? Tooth shape suggests explosive change in modern breeds compared with extinct populations and living Przewalski’s horses

“…With the provisos discussed above, our data indicate that three complementary lines of evidence (mean differences, classification accuracy and morphological disparity) suggest that the size of horse premolars has changed to a variable degree over time and space in both archaic and modern horses (Figures 1c (box plots) and 2 (size phenogram) and Supplementary Information, available online), but changes to shape have been modest, with variation mostly overlapping among the archaic samples (Figures 3 and 4) until the development of modern breeds in recent centuries, when shape has become hugely distinctive (Figures 3 and 4). With an estimated time since the divergence of PRZ and the lineage leading to domestic horses of >100,000 years (Goto et al, 2011; Steiner et al, 2013; but see Der Sarkissian et al, 2015, for an alternative perspective), the data suggest that conservativeness may have characterized premolar shape for almost 99% of the history of Equus caballus , whereas in the last 1000–2000 years, under conditions of strong selective breeding, shape differences have more than doubled compared with those observed in archaic horses (Figure 3). Thus, we propose, for premolar shape, a hypothesis of a ‘long-fuse’ model of phenotypic change in domestication, whereby a long initial period of small variation was followed by an explosive acceleration in the magnitude of shape change.…”

“…The timing of horse domestication around 3500 BCE (Outram et al, 2009), and the subsequent extirpation of wild progenitors, potentially correlates with important environmental shifts, that is, expansion and contraction of forest cover (Warmuth et al, 2011). However, reconstructing the history of this event has proved challenging (Lippold et al, 2011; Steiner et al, 2013; Wade et al, 2009); a deeper knowledge of the processes that underpinned horse domestication has important implications for our understanding of both the human groups that first undertook this particular domestication event (or events) and the ecological setting within which domestication was initiated. Critically, with the expansion of domestic populations, our ability to distinguish between discrete groups of wild and domestic horses diminishes to nil (Bendrey, 2012).…”

The ultrastructure of the tooth enamel of small Equus of the “tarpan” group and their possible phylogenetic connections

“…The history and evolution of equines is relatively well studied, especially of the genus Equus. At the same time, there are always contemporary problems to discuss within taxonomy, systematics, the evolution of equines, and the genus Equus (Forsten 1988, Kuzmina 1997, Spassov and Iliev 1998, Burke et al 2003, Schulz and Kaiser 2013, Steiner et al 2013, Croitor 2018. The proposed schemes of taxonomy and the reconstruction of phylogenetic relationships between particular groups of horses are usually based on different morphological features, and are debatable.…”