European Genotype Samples
During the Bronze Age, Chestnut, Chestnut Sabino, Bay Sabino, and Bay Tobiano horses emerged in the European 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.
Six of the twelve 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 six fossils (Mic1) was discovered to have a dominant mutation at the Tobiano Gene locus (KIT13) leading to the emergence of the Bay Tobiano phenotype. Also, one of these six fossils (Mic5) was discovered to have a dominant mutation at the Sabino Locus (KIT16) leading to the emergence of the Bay Sabino phenotype.
Three of the twelve 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, three of the twelve horses sampled contained a 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. One of the fossils with the base coat color of Chestnut also had a mutation at the Sabino Locus, resulting in the emergence of the Chestnut Sabino phenotype.
None of the horse fossils showed any evidence of having the Overo (EDNRB), Cream (MATP), or either variation of the Silver Gene (SILV9 and SILV11).