An aurochs skull. Image: Dan Bradley
Julius Ceaser once called the aurochs ‘extraordinary’. Now ancient DNA is unlocking secrets of this mysterious beast.
A genetic analysis of aurochs – the predecessors to modern cattle – led by Prof Dan Bradley at Trinity College Dublin’s (TCD) School of Genetics and Microbiology has revealed that the extinct cattle species was more genetically diverse than previously thought.
Aurochs, famous from early-human cave paintings, went extinct approximately 400 years ago, leaving much of their evolutionary history a mystery.
However, the TCD study, in collaboration with international partners, analysed 38 genomes harvested from aurochs bones dating across 50 millennia and spread from Siberia to Britain. The researchers found that the European aurochs, who were previously considered as just one type, actually consisted of three distinct populations – Western European, Italian and Balkan.
“Through the sequencing of ancient DNA, we have gained detailed insight into the diversity that once thrived in the wild as well as enhanced our understanding of domestic cattle,” said Dr Conor Rossi from TCD, first author on the project study just published in Nature Communications.
Although fossils of aurochs found in Europe date back 650,000 years ago, around the time when early human species appeared on the continent, aurochs from the east and west extremes of Eurasia share a much more recent common ancestry – indicating a migration from a South Asian homeland around 100,000 years ago, the study revealed.
Effect of climate change and human activities
The last ice-age that started around 100,000 years ago seemed to caused the European and North Asian aurochs populations to diverge. Genomic estimations showed that the aurochs population dropped during the glacial period, with the European herds being hit particularly hard.
The two populations did not mix until the world warmed up again at the ice-age’s ending, about 11,000 years ago.
Moreover, human domestication after the ice age caused the strongest drop in genetic diversity among the different aurochs herds. Only a handful of maternal lineages (as seen via mitochondrial DNA which is handed down via mothers to their offspring) has come through this process into the cattle gene pool, the researchers note.
“However, the narrow genetic base of the first cattle was augmented as they first travelled with their herders west, east and south,” Bradley said.
“It is clear that there was early and pervasive mating with wild aurochs bulls, leaving a legacy of the four separate preglacial aurochs ancestries that persists among the domestic cattle of today.”
Julius Caesar once described aurochs as “little below the elephant in size”. He was amazed at the animal’s strength and speed, calling it “extraordinary”.
“They spare neither man nor wild beast which they have espied,” he said.
“Although Caesar exaggerated when he said it was like an elephant,” Bradley said, “the wild ox must have been a highly dangerous beast and this hints that its first capture and taming must have happened with only a very few animals.”
Ancient DNA is unlocking many secrets of the past for researchers. Earlier this year, TCD PhD student Louis L’Hôte led a study into an 8,000-year-old sheep bone that uncovered secrets about a harmful bacteria that may have evolved along with the development of farming and typically affects sheep, goats and humans.
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