Wednesday, September 21, 2016

How an ancient pope helped make chickens fat

Today, chicken is one of the most consumed meats around the world. People eat chicken in a variety of ways, ranging from chicken cordon bleu, chicken Caesar salad, and Chick-fil-A sandwiches. Chickens have been domesticated for years, but they were skinnier and less common as a food. In 2010, a worldwide study of the genomes of multiple populations of chickens showed that modern chickens had two copies of the dominant gene, thyroid stimulating hormone receptor (TSHR). This gene makes a protein that attaches to the thyroid stimulating hormone and controls the development and function of the thyroid. In chickens, the expression of TSHR contributes to their growth, reproduction, and metabolism. These chickens are not only larger but also they lay eggs more frequently.

A pair of modern chickens

Scientists found that all domesticated chickens have the two alleles of TSHR. The amount of domesticated chickens containing the TSHR gene spiked during the medieval era in Europe. This occurred due to the Benedictine reform in the United Kingdom. Religious fasting for Christians was required and eating four-legged animals was prohibited. However, two-legged animals were acceptable to eat. That is how chickens became widely consumed and bred. Over time, the fatter chickens that reproduced more eggs had the TSHR gene and the traits were passed down. 

Today, this genetic prevalence of the TSHR gene shows the human role in selection. Naturally, people wanted to eat the fatter chickens and the chickens who would lay eggs every day. Unbeknownst to us at the time, chickens who satisfied these "requirements" had the TSHR gene. As these chickens bred, they reproduced offspring who also had the dominant genetic traits. I think this evolution of chicken genomics is fascinating because it demonstrates how human decisions have impacted chickens today. The consumption of chicken following the Benedictine reform puts into perspective the correlation of the influence of artificial selection on modern genetics. 


  1. Very informative article on how the genes within my chicken have evolved throughout the years.
    I think chicken genomics functions in similar ways as human genomics do, in that: we too have a gene that codes for a protein that attaches to a thyroid stimulating hormone for its developmental control and function. Itd be cool to see an association of this study related to humans too. Itd also be interesting to see if the genetic sequences for the TSHR gene are affected by DNA methylation.