How much introgression from wild aurochs was there in Europe?

Taurine cattle were domesticated in the Fertile Crescent in the Near East. As “breeding-back” focuses on the European aurochs, it is an important question how much introgression from local aurochs populations into the domestic gene pool there was in Europe. Especially as some claim “breeding-back” is doomed to fail because it focuses on the European type while domestic cattle descend from the Near Eastern aurochs. 

 

To assess the question if there was local influence from European aurochs into the modern taurine cattle population, the genetic evidence has to be taken into account. The mitochondrial DNA tells us about the possible matrilineal introgression from local aurochs. There were two separate mitochondrial groups of European aurochs, Bos primigenius primigenius. Southern European and Near Eastern aurochs share the mitochondrial haplotype T, which is also found in most domestic cattle, while Central, Northern and Eastern European aurochs have the haplotype P [1]. The P haplotype was discovered in Holstein cattle and the Korean Hanwoo [1,2], what suggests introgression from wild cows of the northern type. Some Italian breeds also have the haplotypes R and Q, which are unique among domestic cattle [3,4]. This suggests local introgression or even domestication of wild aurochs in Italy [4]. 

Regarding the patrilineal evidence, it has been suggested in 2005 that introgression from aurochs bulls into domestic cattle was common in Europe [5], which was refuted later [6]. 

It has to be kept in mind that mitochondrial and Y-chromosomal haplotypes only tell half of the story. The mitochondrial genome is passed on by the mother exclusively, and the Y chromosome only by the father. Thus, looking only at mitochondrial or Y-chromosomal haplotypes can be misleading. If aurochs bulls mated with domestic cows, which is not unlikely as cattle were kept free all year round in earlier times (and still are today in some regions of Europe), which is also historically documented to have happened (Anton Schneeberger mentioned that occasionally wild aurochs bulls covered domestic cows in the 16^th century), and if only the female offspring was kept for further breeding (which is also not unlikely because the behaviour of the hybrid bulls was certainly more problematic than that of the cows), the wild influence would be undetectable by mitochondrial and Y-chromosomal haplotypes. The aurochs would not pass on aurochs mtDNA, and the Y-chromosome would be selected out in the first generation. Thus it is possible or even likely that introgression from local wild aurochs was more common in Europe than suggested by mitochondrial and Y-chromosomal haplotypes. Therefore, not only these parts of the genome should be considered to look for local aurochs introgression, but also the autosomal genome. 

Not surprisingly, when the first nuclear aurochs genome was fully sequenced [7], it was found that British aurochs significantly influenced British and Irish landraces [7,8]. 

 

Therefore, hybridization between local aurochs and domestic cattle not only happened occasionally, but the offspring was actively included into the breeding by ancient farmers. It is possible that the influence of local aurochs contributed alleles useful for the breeding, f.e. adaptions to local climate and diseases that were beneficial for the cattle from the Near East. Consequently, modern European taurine cattle are not only the descendants of the Near Eastern aurochs, but also of the European aurochs. The European aurochs left living descendants. 

 

 

Literature 

 

[1] Mona et al.: Population dynamic of the extinct European aurochs: genetic evidence from a north-south differentiation pattern and no evidence of post-glacial expansion. 2010. 

[2] Zhang et al.: Evolution and domestication oft he Bovini species. 2020.

[3] Park et al.: Genome sequencing of the extinct Eurasian wild aurochs, Bos primigenius, illuminates the phylogeography and evolution of cattle. 2015.

[4] Bonfiglio et al.: The enigmatic origin of bovine mtDNA haplogroup R: Sporadic interbreeding or an independent event of Bos primigenius domestication in Italy? 2010. 

[5] Götherström et al.: Cattle domestication in the Near East was followed by hybridiziation with aurochs bulls in Europe. 2005. 

[6] Edwards et al.: Mitochondrial DNA analysis shows a Near Eastern Neolithic origin for domestic cattle and no indication of domestication of European aurochs. 2007. 

[7] Orlando, L.: The first aurochs genome reveals the breeding history of British and European cattle. 2015. 

[8] Park et al.: Genome sequencing of the extinct Eurasian wild aurochs, Bos primigenius, illuminates the phylogeography and evolution of cattle. 2015.