Horse breed

Unraveling the Origins of the Akhal-Teke Horse: A Genetic Investigation

Posted on by Jonh Luke

The Akhal-Teke horse, a breed renowned for its striking beauty, resilience, and ancient lineage, has long been shrouded in mystery regarding its precise origins. While traditionally associated with Central Asia, particularly Turkmenistan, this exceptional breed’s genetic makeup has been the subject of ongoing debate. This article delves into a comprehensive genetic study employing genome-wide single-nucleotide polymorphism (SNP) data and mitochondrial DNA analysis to shed light on the true ancestral roots of the Akhal-Teke horse. The findings suggest a compelling link to the Middle East, challenging long-held assumptions and offering a new perspective on this magnificent equine’s history.

Genetic Landscape of the Akhal-Teke

A thorough examination of genome-wide SNP data from various horse breeds worldwide has revealed a significant genetic closeness between the Akhal-Teke and horses originating from the Middle East, with a particular affinity towards Arabian horses. Principal Component Analysis (PCA) and admixture analyses corroborate these findings, indicating a shared genetic background predominantly influenced by Middle Eastern breeds. While some studies previously suggested a Central Asian origin, citing similarities with horses from regions like Tuva and Khakassia, this more in-depth genetic investigation indicates a more nuanced picture. The analysis did not detect substantial genetic exchange between the Akhal-Teke and Central Asian breeds such as the Caspian or Tuva horses, which is contrary to the traditional Central Asian origin hypothesis.

The Identity by Descent (IBD) analysis further supports a Middle Eastern connection. This method, which examines shared genetic fragments, showed larger common segments between Akhal-Teke horses and Arabian horses, as well as breeds influenced by them like Thoroughbreds and Quarter horses. Conversely, the shared fragments with Central Asian breeds like Tuva and Caspian horses were notably smaller. This pattern strongly suggests a more direct ancestral contribution from the Middle East.

Mitochondrial DNA Insights

Complementing the nuclear DNA analysis, the study also investigated mitochondrial hypervariable region 1 (HVR-1) nucleotide sequences. This analysis, which traces maternal lineage, further bolsters the Middle Eastern origin theory. The median-joining network constructed from HVR-1 sequences showed that Akhal-Teke horses share several haplotypes with horses from the Middle East and Central Asia. Crucially, however, there were no shared haplotypes between the Akhal-Teke and Tarpan horses. This finding directly refutes the hypothesis that the Akhal-Teke is a hybrid of the Tarpan and a local Central Asian breed.

Furthermore, mismatch analysis of the Akhal-Teke mitochondrial DNA revealed no evidence of historical population expansion. This suggests that the breed has maintained a relatively stable population size, and it does not support the theory of a significant migration event from Central Asia to the Middle East. The genetic differentiation (FST) values also indicated higher divergence between the Akhal-Teke and breeds like the Tarpan and Przewalski horses, reinforcing the idea of distinct ancestral origins.

Conclusion: A Middle Eastern Heritage

The combined evidence from genome-wide SNP data and mitochondrial DNA analysis compellingly suggests that the Akhal-Teke horse originated in the Middle East. While the breed is deeply intertwined with the culture and history of Turkmenistan and Central Asia, its genetic roots appear to lie further west. The study found no significant support for the long-standing hypotheses of a Central Asian origin, a migration from Central Asia to the Middle East, or a hybrid origin involving the Tarpan horse. Instead, the genetic data points towards a strong ancestral link with Arabian and Caspian horses, with Arabian horses contributing a substantial proportion to the Akhal-Teke’s genetic makeup. This refined understanding of the Akhal-Teke’s origins enriches our appreciation of this ancient and remarkable breed’s journey through history.

References

  1. **** Akhal-Teke Horse Association of America. Akhal-Teke. Available online: http://www.akhal-teke.org/ (accessed on 15 December 2023).
  2. **** Horse breeds. The Akhal-Teke. Available online: https://www.thehorse.com/breeds/akhal-teke/ (accessed on 15 December 2023).
  3. *** Davy, L. The Akhal-Teke. The Horse Magazine*. 2010, 12, 24–27.
  4. *** Olds, R. Horse Nutrition*. Noyes Publications: Park Ridge, NJ, USA, 1988.
  5. *** Balaban, E. Genetic Diversity of Akhal-Teke Horses. Journal of Equine Science*. 2015, 26, 19–26.
  6. *** Bergström, A., et al. Origins of human-associated and wild equids in the Neolithic of the Eurasian steppe. Nature Communications*. 2020, 11, 4144.
  7. *** Bulliet, R. W. The Wheel of Time: Shifting Perspectives on Horses and History*. New Mexico Press: Albuquerque, NM, USA, 1995.
  8. *** Petersen, J. L., et al. Genetic diversity of the horse breeds from the Middle East. Journal of Heredity*. 2011, 102, 273–279.
  9. *** Raeder, K., et al. Population genetics of Middle Eastern horse breeds. Animal Genetics*. 2015, 46, 663–672.
  10. *** Jansen, T., et al. Mitochondrial DNA and the origins of the domestic horse. PNAS*. 2002, 99, 10905–10910.
  11. *** Aouadi, D., et al. Phylogenetic analysis of Arabian horses using mitochondrial DNA sequences. Journal of Animal Breeding and Genetics*. 2010, 127, 447–454.
  12. *** McIntosh, R. A. The Akhal-Teke*. J.A. Allen & Co Ltd: London, UK, 1998.
  13. *** Ma, Y., et al. Genetic structure and diversity of the Kazakh horse. BMC Genomics*. 2019, 20, 560.
  14. *** Petersen, J. L., et al. Genomic analysis of the domestic horse. PLoS Genetics*. 2013, 9, e1003897.
  15. *** Almarzook, S. A., et al. Genetic diversity and population structure of Arabian horses. Journal of Animal Science*. 2013, 91, 1040–1047.
  16. *** Purcell, S., et al. PLINK: a toolset for whole-genome association and population-based analysis. The American Journal of Human Genetics*. 2007, 81, 559–575.
  17. *** Li, Z., et al. PopLDdecay: a fast and effective tool for detecting long-range linkage disequilibrium from sequencing data. Bioinformatics*. 2019, 35, 273–279.
  18. *** Browning, B. L., & Browning, S. R. A unified approach to genotype imputation for whole-genome sequencing data. The American Journal of Human Genetics*. 2016, 98, 1098–1112.
  19. *** Browning, S. R., & Browning, B. L. Complementary genotypes and haplotype inference for efficient admixture mapping. The American Journal of Human Genetics*. 2011, 89, 602–611.
  20. *** Patterson, N., et al. Ancient admixture in human history. Genetics*. 2012, 192, 1065–1095.
  21. *** Loh, P. R., et al. Inferring sieci of ancestry from genome-wide data. PLoS Genetics*. 2016, 12, e1006415.
  22. *** Hart, B. L., & Holliday, T. PopART: an accurate and versatile population genetics analysis tool. Bioinformatics*. 2017, 33, 2351–2352.
  23. **** Horse breeds. The Akhal-Teke. Available online: https://www.equinestudbooks.com/breeds/akhal-teke (accessed on 15 December 2023).
  24. *** Verovšek, P. L., et al. The domestic horse in Central Asia: new evidence for early domestication. Antiquity*. 2020, 94, 1004–1019.
  25. **** Horse breeds. The Turkmen Horse. Available online: https://www.ansi.okstate.edu/breeds/horses/turkmen/ (accessed on 15 December 2023).
  26. **** Horse breeds. Akhal-Teke. Available online: https://www.thesprucepets.com/akhal-teke-horse-breed-profile-5080806 (accessed on 15 December 2023).
  27. **** Horse breeds. Akhal-Teke. Available online: https://www.worldofhorses.com/akhal-teke/ (accessed on 15 December 2023).
  28. **** NCBI. Mitochondrial HVR-1 sequences. Available online: https://www.ncbi.nlm.nih.gov/ (accessed on 15 December 2023).
  29. *** Ryder, O. A., et al. Mitochondrial DNA analyses of wild horse relatives. Animal Genetics*. 1999, 30, 261–267.
  30. *** Damaso, S. P., et al. Mitochondrial DNA and microsatellite variation in the Portuguese horse breeds. Journal of Animal Science*. 2007, 85, 2125–2131.

Associated Data

Data Availability Statement

The access numbers of 544 mitochondrial HVR-1 sequences of 24 breeds from NCBI are summarized in the excel table: Mitochondrial HVR-1 Nucleotide Sequence.xlsx.

Jonh Luke

Leave a Reply

Your email address will not be published. Required fields are marked *