WHICH came first: the chicken or the egg? Modern science may have answered that age-old mystery, but now the evolution of the domesticated chicken, as we know it today, has been pinpointed to the fasting habits of Benedictine monks more than a millennium ago.
In a study, published last week in the journal Molecular Biology and Evolution by Oxford University Press, a team of 12 international scientists have linked the Rule of St Benedict (c.480) — which forbade monks in Europe to consume meat from four-legged animals during fasting periods, but allowed for the consumption of birds, eggs, and fish — to the evolution of the passive, fast-laying chickens farmed today.
Researchers analysed archaeological records, which documented a significant increase of chicken bones from the ninth century onwards, to develop a new model for studying chicken DNA. This model was then used to detect an increase in the thyroid-stimulating hormone receptor (TSHR), which is understood to effect faster egg-laying and reduced aggression in chickens.
The study suggests that only 40 per cent of chickens were estimated to carry the TSHR variant 1100 years ago, but that this began to increase in about 920, so that, today, almost 100 per cent of modern domesticated chickens display characteristics associated with TSHR.
The author of the study, Anders Eriksson, says: “The significant intensification of chicken and egg production, evident in the medieval European archaeological record, has been linked to Christian fasting practices. . . These rules, which originated in the Benedictine monastic order, became widely adopted across Europe due to the increasing political influence of the Catholic Church, and applied to all segments of society circa 1000 AD.”
Urbanisation and population growth, alongside more efficient agricultural practices, may also be linked to the increase of chicken production and consumption in the Middle Ages, he says.
Greger Larson, who led the research team, said: “This study demonstrates just how easy it is to drive a trait to a high frequency in an evolutionary blink of an eye, and suggests that, simply because a domestic trait is ubiquitous, it may not have been a target for selection at the very beginning of the domestication process.”