April 18, 2014
Wild Vs Domestic: Wild Animals Interbred With Domesticated Ones Until Quite Recently
Brett Smith for redOrbit.com - Your Universe Online
Previous theories have posited that domesticated animals have been cut off from their wild counterparts, but a new study slated for publication in the Proceedings of the National Academy of Sciences journal has found that wild and domestic animals have interbred more than previously thought.
"Our findings show little control of breeding, particularly of domestic females, and indicate long-term gene flow, or interbreeding, between managed and wild animal populations," study author Fiona Marshall, professor of anthropology at Washington University in St. Louis said in a recent statement.
"Our livestock is losing genetic diversity even faster than some wild animals, because of management practices like artificial insemination," Marshall added. "We took only a bit of the diversity from the wild for domestication, and what we're looking at now is lopping it off really fast so we'll be left with little diversity to survive all the climate and disease issues we're facing.”
Marshall explained that artificial selection of cattle, sheep or other large herbivores was probably fairly weak.
"Herders could not afford to kill many animals, particularly large-bodied animals with long gestation periods. To keep herd size stable, herders probably culled or castrated males surplus to the growth needs of the herd, allowing all females to breed," she said.
At the same time, the forces of natural selection on these animals’ wild counterparts were probably not as severe as the forces acting on domestic herds, the study team said. For example, early herds were probably decimated by disease, weather and natural disasters. These factors would have forced early herders to turn to wild animals to replenish their stocks.
The researchers cited the domestication of pigs as evidence of the intermingling between wild animals and domestic stocks. Through a DNA analysis, the researchers found that domestic pigs were brought from modern-day Turkey to Western Europe, where they interbred with the wild boars. These hybridized pigs eventually replaced the original breeds, first in Europe and then back into Asia Minor.
In China, domestic pigs were found not to have interbred with wild stocks. The researchers said this was probably due to the Chinese practice of keeping pigs in pens – unlike European pig farmers who routinely took their animals into the forest for foraging.
"The research is really exciting because it is making us completely rethink what it means to be domesticated," Marshall said. "The boundaries between wild and domesticated animals were much more blurred for much longer than we had realized."
"To untangle the history of domestication," said study author Tim Denham, of the Australian National University, "scientists will need to bring to bear all of the evidence at their disposal, including archeological and ethnographic evidence, and the analysis of both modern and ancient DNA."
"We must also investigate sources of selection more critically," Marshall said, "bearing in mind the complex interplay of human and environmental selection and the likelihood of long-term gene flow from the wild."
The study team noted that their work expanded on that of Charles Darwin – who took a comparatively simplistic view of animal breeding and domestication.
Citation: “The Modern View of Domestication,” a special issue of PNAS edited by Greger Larson and Dolores R. Piperno, resulted from a meeting entitled “Domestication as an Evolutionary Phenomenon: Expanding the Synthesis,” held April 7–11, 2011, that was funded and hosted by the National Evolutionary Synthesis Centre (National Science Foundation EF-0905606) in 2011.