Ancient DNA reveals traces of Iberian Neolithic and Bronze Age lineages in modern Iberian horses

Abstract

Multiple geographical regions have been proposed for the domestication of Equus
caballus. It has been suggested, based on zooarchaeological and genetic analyses that wild
horses from the Iberian Peninsula were involved in the process, and the overrepresentation
of mitochondrial D1 cluster in modern Iberian horses supports this suggestion. To
test this hypothesis, we analysed mitochondrial DNA from 22 ancient Iberian horse
remains belonging to the Neolithic, the Bronze Age and the Middle Ages, against
previously published sequences. Only the medieval Iberian sequence appeared in the D1
group. Neolithic and Bronze Age sequences grouped in other clusters, one of which
(Lusitano group C) is exclusively represented by modern horses of Iberian origin.
Moreover, Bronze Age Iberian sequences displayed the lowest nucleotide diversity values
when compared with modern horses, ancient wild horses and other ancient domesticates
using nonparametric bootstrapping analyses. We conclude that the excessive clustering of
Bronze Age horses in the Lusitano group C, the observed nucleotide diversity and the local
continuity from wild Neolithic Iberian to modern Iberian horses, could be explained by
the use of local wild mares during an early Iberian domestication or restocking event,
whereas the D1 group probably was introduced into Iberia in later historical times.