5 millennia of horse management and genetics

Angela

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Antoine Fages et al"

"[h=1]Tracking Five Millennia of Horse Management with Extensive Ancient Genome Time Series[/h]
"[h=2]Highlights[/h]
  • Two now-extinct horse lineages lived in Iberia and Siberia some 5,000 years ago
  • Iberian and Siberian horses contributed limited ancestry to modern domesticates
  • Oriental horses have had a strong genetic influence within the last millennium
  • Modern breeding practices were accompanied by a significant drop in genetic diversity

[h=2]Summary[/h]Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (≥1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modern legacy of past equestrian civilizations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN “speed gene,” only rose in popularity within the last millennium. Finally, the development of modern breeding impacted genetic diversity more dramatically than the previous millennia of human management."

"The earliest archaeological evidence of horse milking, harnessing, and corralling is found in the ∼5,500-year-old Botai culture of Central Asian steppes (Gaunitz et al., 2018
, Outram et al., 2009
; see Kosintsev and Kuznetsov, 2013
for discussion). Botai-like horses are, however, not the direct ancestors of modern domesticates but of Przewalski’s horses (Gaunitz et al., 2018
). The genetic origin of modern domesticates thus remains contentious, with suggested candidates in the Pontic-Caspian steppes (Anthony, 2007
), Anatolia (Arbuckle, 2012
, Benecke, 2006
), and Iberia (Uerpmann, 1990
, Warmuth et al., 2011
). Irrespective of the origins of domestication, the horse genome is known to have been reshaped significantly within the last ∼2,300 years (Librado et al., 2017
, Wallner et al., 2017
, Wutke et al., 2018
). However, when and in which context(s) such changes occurred remains largely unknown."

"his revealed that Y chromosome nucleotide diversity (π) decreased steadily in both continents during the last ∼2,000 years but dropped to present-day levels only after 850–1,350 CE (Figures 2B and S2E; STAR Methods). This is consistent with the dominance of an ∼1,000- to 700-year-old oriental haplogroup in most modern studs (Felkel et al., 2018
, Wallner et al., 2017
). Our data also indicate that the growing influence of specific stallion lines post-Renaissance (Wallner et al., 2017
) was responsible for as much as a 3.8- to 10.0-fold drop in Y chromosome diversity."

"to clarify the historical contexts that most impacted Y chromosome diversity. This confirmed the temporal trajectory observed above as Byzantine horses (287–861 CE) and horses from the Great Mongolian Empire (1,206–1,368 CE) showed limited yet larger-than-modern diversity. Bronze Age Deer Stone horses from Mongolia, medieval Aukštaičiai horses from Lithuania (C9th–C10th [ninth through the tenth centuries of the Common Era]), and Iron Age Pazyryk Scythian horses showed similar diversity levels (0.000256–0.000267) (Figure 2A). However, diversity was larger in La Tène, Roman, and Gallo-Roman horses, where Y-to-autosomal π ratios were close to 0.25. This contrasts to modern horses, where marked selection of specific patrilines drives Y-to-autosomal π ratios substantially below 0.25 (0.0193–0.0396) (Figure 2A). The close-to-0.25 Y-to-autosomal π ratios found in La Tène, Roman, and Gallo-Roman horses suggest breeding strategies involving an even reproductive success among stallions or equally biased reproductive success in both sexes (Wilson Sayres et al., 2014
)."

"We next tracked evidence for animal exchange between past cultures by mapping genetic variation through space and time. We included all samples belonging to a particular archaeological culture, as long as they collectively accumulated a minimal genome depth-of-coverage of 2-fold (n = 186, Table S5). TreeMix reconstructions (Pickrell and Pritchard, 2012
) revealed that modern Shetland and Icelandic ponies were most closely related to a group of north European horses including pre-Viking Pictish horses from C6th–C7th Britain, Viking horses, and one C9th–C10th horse from Estonia (Saardjave) (Figure 3; STAR Methods). This is in line with the historical expansion of Scandinavian seafaring warriors in the British Isles and Iceland between the late C8th–C11th (Brink and Price, 2008
). These horses formed a sister clade to mainland European horses spanning the Iron Age to the C7th and a number of cultures, including in the La Tène and (Gallo-) Roman periods. Other modern European native breeds (e.g., Friesian, Duelmener, Sorraia, and Connemara) were found to belong to yet another clade, first appearing in Europe at Nustar, Croatia in the C9th, but not present at that time in northern Europe (Aukštaičiai, Lithuania). This suggests the introduction of new domestic lineages to the south of mainland Europe between the C7th–C9th, a time strikingly coincident with the peak of Arab raids on the Mediterranean coasts, including Croatia (Skylitzes and Wortley, 2010
). This, and the earliest identification of this clade within two Sassanid Persian horses from Shahr-I-Qumis, Iran (C4th–C5th), supports the growing influence of oriental bloodlines in mainland Europe following at least the C9th."

"Moving focus to Asia, steppe Iron Age Pazyryk Scythian and Xiongnu horses appear related to Karasuk horses, locally present in the Minusinsk Basin of South Siberia during the late Bronze Age (Mallory and Adams, 1997
). This lineage of horses survived at least until the C8th in Central Asia at Boz Adyr, Kyrgyzstan. However, Mongolian horses from the Uyghur (C7th–C9th, Khotont_UCIE2012x85_1291) and the Great Mongolian Empire (C13th) clustered together with C9th horses from Kazakhstan (Gregorevka4_PAVH2_1192 and Zhanaturmus_Issyk1_1143) within the group descending from the two Shahr-I-Qumis Sassanid Persian horses. Therefore, the population shift observed in Europe during the C7th–C9th was also mirrored in Central Asia and Mongolia."

"PCA revealed that native Iberian horses (IBE) from the 3rd and early 2nd mill. BCE cluster separately from E. lenensis, Przewalski’s horses (and their Botai-Borly4 ancestors) and the lineage leading to modern domesticates (DOM2) (Figure 5A; STAR Methods). This indicates that a fourth lineage of horses existed during the early phase of domestication (Gaunitz et al., 2018
, Outram et al., 2009
). Members of this lineage possess their own distinctive mtDNA haplogroup (Figure 6A; STAR Methods) and are represented by two Spanish pre-Bell Beaker Chalcolithic settlements (Cantorella and Camino de Las Yeseras) and a Bronze Age village (El Acequión), with archaeological contexts compatible with both wild and domestic status."

"We found that Y chromosome diversity in horses declined steadily within the last ∼2,000 years, with male reproductive success becoming skewed following the (Gallo-) Roman period. This indicates that breeders increasingly chose specific stallions for breeding from the Middle Ages onward, consistent with the dominance of an ∼700 to 1,000-year-old Arabian haplogroup in most modern studs (Felkel et al., 2018
, Wallner et al., 2017
). Together with the increasing affinity to Sassanid Persian horses detected in the genomes of European and Asian horses after the C7th–C9th, this suggests that the Byzantine-Sassanid wars and the early Islamic conquests significantly impacted breeding and exchange. The legacy of these historical events has persisted until now as the majority of the modern breeds investigated here clustered within a phylogenetic group related to Sassanid Persian horses. During the same time period, the horse phenotype was also significantly reshaped, especially for locomotion, speed capacity, and morpho-anatomy. Whether this partly or fully reflects the direct influence of Arabian lines requires further tests."
 
joke-1: so IE came fron Arabia as the main lineage is from there
joke-2: so Iberian BB were exporting with Amazon (no genetic track), pots, weapons and horses... if people was so eager to take the Iberian fashion, why no the language also?

no kidding here, seems as if DOM2 would be a secondary domestication, something like zebus in the Indian subcontinent.
 

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