Wallner, B., Brem, G., Muller, M., & Achmann, R. (2003). Fixed nucleotide differences on the Y chromosome indicate clear divergence between Equus przewalskii and Equus caballus. Anim Genet, 34(6), 453–456.
Abstract: The phylogenetic relationship between Equus przewalskii and E. caballus is often a matter of debate. Although these taxa have different chromosome numbers, they do not form monophyletic clades in a phylogenetic tree based on mtDNA sequences. Here we report sequence variation from five newly identified Y chromosome regions of the horse. Two fixed nucleotide differences on the Y chromosome clearly display Przewalski's horse and domestic horse as sister taxa. At both positions the Przewalski's horse haplotype shows the ancestral state, in common with the members of the zebra/ass lineage. We discuss the factors that may have led to the differences in mtDNA and Y-chromosomal observations.
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Gaunitz, C., Fages, A., Hanghøj, K., Albrechtsen, A., Khan, N., Schubert, M., et al. (2018). Ancient genomes revisit the ancestry of domestic and Przewalski's horses. Science, 360(6384), 111–114.
Abstract: The Eneolithic Botai culture of the Central Asian steppes provides the earliest archaeological evidence for horse husbandry, ~5,500 ya, but the exact nature of early horse domestication remains controversial. We generated 42 ancient horse genomes, including 20 from Botai. Compared to 46 published ancient and modern horse genomes, our data indicate that Przewalski's horses are the feral descendants of horses herded at Botai and not truly wild horses. All domestic horses dated from ~4,000 ya to present only show ~2.7% of Botai-related ancestry. This indicates that a massive genomic turnover underpins the expansion of the horse stock that gave rise to modern domesticates, which coincides with large-scale human population expansions during the Early Bronze Age.
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Kräußlich, H., & Brem, G. (1997). Tierzucht und allgemeine Landwirtschaftslehre für Tiermediziner. Stuttgart: Enke.
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Wallner, B., Palmieri, N., Vogl, C., Rigler, D., Bozlak, E., Druml, T., et al. (2017). Y Chromosome Uncovers the Recent Oriental Origin of Modern Stallions. Current Biology, 27(13), 2029–2035.e5.
Abstract: The Y chromosome directly reflects male genealogies, but the extremely low Y chromosome sequence diversity in horses has prevented the reconstruction of stallion genealogies [1, 2]. Here, we resolve the first Y chromosome genealogy of modern horses by screening 1.46 Mb of the male-specific region of the Y chromosome (MSY) in 52 horses from 21 breeds. Based on highly accurate pedigree data, we estimated the de novo mutation rate of the horse MSY and showed that various modern horse Y chromosome lineages split much later than the domestication of the species. Apart from few private northern European haplotypes, all modern horse breeds clustered together in a roughly 700-year-old haplogroup that was transmitted to Europe by the import of Oriental stallions. The Oriental horse group consisted of two major subclades: the Original Arabian lineage and the Turkoman horse lineage. We show that the English Thoroughbred MSY was derived from the Turkoman lineage and that English Thoroughbred sires are largely responsible for the predominance of this haplotype in modern horses.
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