A team of geneticists from the National Museum of Natural History in France, the University of Mainz in Germany, and UCL in the UK, excavated the bones of domestic cattle on archaeological sites in Iran, and then compared those to modern cows. They looked at how differences in DNA sequences could have arisen under different population history scenarios, modelled in computer simulations.
The team found that the differences that show up between the two populations could only have arisen if a relatively small number of animals — approximately 80 — had been domesticated from a now-extinct species of wild ox, known as aurochs, that roamed across Europe and Asia. Those cattle were then bred into the 1.4 billion cattle estimated by the UN to exist in mid-2011.
The process of collecting the data was tricky. Ruth Bollongino, lead author of the study, said in a press release: "Getting reliable DNA sequences from remains found in cold environments is routine. That is why mammoths were one of the first extinct species to have their DNA read. But getting reliable DNA from bones found in hot regions is much more difficult because temperature is so critical for DNA survival. This meant we had to be extremely careful that we did not end up reading contaminating DNA sequences from living, or only recently dead cattle."
The research has implications for the study of the history of domestication. Mark Thomas, geneticist and an author of the study, said in the release: "This is a surprisingly small number of cattle. We know from archaeological remains that the wild ancestors of modern-day cattle were common throughout Asia and Europe, so there would have been plenty of opportunities to capture and domesticate them."
However, it tallies with existing research on the matter. Jean-Denis Vigne, a CNRS bio-archaeologist and author on the study, said in the release: "A small number of cattle progenitors is consistent with the restricted area for which archaeologists have evidence for early cattle domestication 10,500 years ago. This restricted area could be explained by the fact that cattle breeding, contrary to, for example, goat herding, would have been very difficult for mobile societies, and that only some of them were actually sedentary at that time in the Near East." [Wired]
Image: saturn h/Flickr