Date: May 2, 2017
Source: Molecular Biology and Evolution (Oxford University Press)
Chickens were domesticated from Asian jungle fowl around 6000 years ago. Since domestication they have acquired a number of traits that are valuable to humans, including those concerning appearance, reduced aggression and faster egg-laying, although it is not known when and why these traits evolved.
Now, an international team of scientists has combined DNA data from archaeological chicken bones with statistical modeling to pinpoint when these traits started to increase in frequency in Europe.
"Ancient DNA allows us to observe how genes have changed in the past, but the problem has always been to get high enough time resolution to link genetic evolution to potential causes. But with enough data and a novel statistical framework, we now have timings that are precise enough to correlate them with ecological and cultural shifts." says Liisa Loog, the first author of the study.
To their surprise they found that this happened in High Middle Ages, around 1000 A.D. Intriguingly these strong selection pressures coincided with increasing urbanization and Christian edicts that enforced fasting and the exclusion of four legged animals from the menu. Could Medieval religious rules have increased the demand for poultry and thereby altered chicken evolution?