Siberian Genotype Samples
During the Bronze Age, Chestnut, and Bay Sabino horses emerged in the Siberian population. Even though domestication helped the alleles for these phenotypes to increase, there were fewer horses domesticated than in the wild; therefore, the genes for these phenotypes did not increase as rapidly as the emergence of black in the previous time period.
Four of the nine fossils sampled from this time period contained a genotype coding for the base coat
color Bay. These horses all had at least one dominant Extension Genes (E) and at least one copy of the functional Agouti Gene (A). Because these fossils had at least one dominant (functional) copy of each of these genes, their base coat color was Bay. One of these four fossils (TAR 005) was discovered to have a dominant mutation at the Sabino Gene locus (KIT16) leading to the emergence of the Bay Sabino phenotype in Asia.
Three of the nine horses sampled from the time period had a genotype that coded for the Black phenotype. All of the fossils that had the coat color genotype for a black horse had two copies of the non-functional Agouti Gene (a/a) with at least one copy of the functional Extension Gene (E).
Finally, two of the nine horses sampled contained the new genotype coding for the base coat color Chestnut. These fossils all had two non-functional alleles at the Extension Gene Locus (e/e) and any combination of Agouti Alleles. Having two mutated Extension Alleles resulted in the lack of black pigment formation, and instead the production of a yellow-red pigment.
None of the horse fossils showed any evidence of having the Overo (EDNRB), Tobiano (KIT13), Cream (MATP), or either variation of the Silver Gene (SILV9 and SILV11).