Chickens are perhaps the most important model species in the history of biology. Model species are organisms which are used by scientists to observe, predict, or test certain ideas. The secret to their success is twofold; humans have spread chickens around the globe and chickens have many characteristics which make them ideal specimens for research.

One of the chicken’s earliest contributions was to the field of embryology. The Greek philosopher Aristotle incubated and dissected many chicken embryos, developing a theory of epigenesis, or the idea that diverse structures come from one simple structure. Chickens would also be instrumental in another “many from one” theory as Robert Remak first observed cell division when viewing chicken embryonic blood cells.

Although finches typically get credit for starting Darwin’s musings on evolution, it was the chicken which gave him both urgency and a research specimen. Edward Blyth was a friend of Darwin’s who lived in Kolkata (Calcutta). Blyth recently observed several species of junglefowl and noted that one of the varieties had yellow legs and a red comb. He suggested to Darwin that this may be the wild ancestor of the chicken, an idea which Darwin would famously adopt. Blyth had also heard of the work of a nearby scientist named Alfred Russel Wallace. Wallace was studying birds in the Malay Archipelago and noted that different islands had similar birds, but with key differences. These differences correlated to the types of food available on the island. This idea was remarkably like Darwin’s. So similar, that Darwin gave Wallace co-author credits on an 1868 paper. Fifteen months and hundreds of chickens later, Darwin would publish his book On the Origin of Species and the world would never be the same.

Another world-changing biologist lived in Austria during the same time as Darwin, although he would never achieve universal notoriety in his lifetime. Gregor Mendel is now known for his study of the inheritance of peas, but few knew of him outside the fields of entomology and botany. This would all change in the early 20^th century when an English biologist named William Bateson read Mendel’s work while preparing for a conference. His conference presentation, and its subsequent research, would not only make Mendel a household name, but also create the field of genetics. Bateson, his research partner Edith Saunders, and later Reginald Punnett, would study the document the inheritance of pea plants, developing a theory of genetic linkage. Although they initially focused on repeating Mendel’s work, the trio eventually adopted the chicken as their preferred research subject. Punnett would go on to use the chicken as his primary model organism in the book Mendelism, which not only introduced mainstream audiences to Mendel, but also introduced the “Punnett Square.”

After Britain’s entry into the “Great War” in 1914, Punnett believed he could use his knowledge of chickens and genetics to serve his country. Punnett joined the Food Production Department of the Board of Agriculture and began work on a new idea, the use of sex-linked traits in agriculture. At the time chickens were not an efficient source of meat. Instead, most chickens were raised for eggs. This meant that male chickens were discarded to save on the cost of feed. This was a wasteful process as Europeans did not have the capability of determining a chicken’s sex at birth. Instead, growers would have to wait until the birds matured, meaning a lot of feed was consumed by birds which were not useful for meat and didn’t lay eggs. Punnett wanted to develop a chicken breed which would hatch chicks that could be identified as male or female at birth based on their feather coloring. Although he did not do so until after the war, Punnett successfully bred the “Cambar,” the world’s first “auto-sexing” breed.

The Second World War would also lead to developments in poultry genetics. During the war, the US government rationed beef and pork. As a result, most Americans began eating chicken meat as their primary source of animal protein. After the war, Americans wanted their beef and pork back. A&P Food Stores grew concerned that chicken sales would drop dramatically unless they could sell a chicken which had a cut of meat more like a steak. As a result, A&P launched the “Chicken of Tomorrow” contest. This contest was administered by state land-grant schools and invited poultry breeders from across the country to develop a fast growing and meatier bird. During the several years it ran, the Chicken of Tomorrow contest elevated names such as Arbor Acres and Tyson to the top of the poultry industry. The length of time it took to grow out birds went from months, to an average of 47 days. This would transform our relationship with the chicken to what it is today.

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