In this excerpt of Big Chicken: The Incredible Story of How Antibiotics Created Modern Agriculture and Changed the Way the World Eats, author Maryn McKenna chronicles the rise of the backyard chicken to dietary staple.

In 1925 there were more than six million farms in the United States, compared with two million now. They were mostly small properties, growing a mix of crops and animals, and they almost all raised chickens. Which type of chicken was a complicated question, because there were so many to choose from.

The January 1921 issue of the American Poultry Journal carried six pages of small-type classified ads featuring dozens of varieties from hundreds of breeders nationwide: Single-Comb Anconas, Silver Wyandottes, Brown Leghorns, Black Langshans, Light Brahmas, Sicilian Buttercups, Golden Campines, White-Laced Red Cornish, Silver-Gray Dorkings, Silver-Spangled Hamburgs, Mottled Houdans, Mahogany Orloffs, White Minorcas, Speckled Sussex. Most farms kept small flocks, from a few birds up to about 200, and for most of them, the point of chickens was eggs; birds were sold for meat only when hens were spent or when chicks hatched out male. Farmers chose the variety they raised based on what other farmers in their area preferred—breeds that had adapted well to whatever wet or dry, windy or humid conditions prevailed where they lived—or because they were persuaded by boastful ads that talked up the egg production of breeds that won medals at state and national poultry expositions.

View Images Courtesy National Geographic

Chicken production’s first step on the road to innovation, and the expansion that followed it, came in 1923 with the first electrically heated incubator. That freed farmers from having to choose and maintain breeding stock, and also from losing the months in a hen’s short productive life when she would be hatching her eggs instead of laying more. Now they could outsource those tasks to a new tier of the industry, thousands of hatcheries shipping newborn chicks by mail. But the breeds those chicks came from were still selected for maximum egg production, not for any eating pleasure they might offer after their laying years ended.

Choosing birds for how many eggs they could lay was a smart strategy through the privations of the Great Depression and the restrictions of World War II: It maximized the protein you could get from a bird without sacrificing the bird herself. But after the war, when beef and pork emerged from rationing, eggs seemed dull by comparison, and laying hens’ lack of tasty muscle made them an insufficient alternative. People had willingly cut their meat eating for a long time, to support the war. Now they wanted to indulge.

One smart retailer saw the problem coming. Howard C. Pierce, the poultry research director for the A&P Food Stores supermarket chain, told a November 1944 poultry meeting in Canada that someone needed to develop a sumptuous chicken, a bird with a breast like a turkey’s. By the next summer, his wish ignited an extraordinary undertaking: the Chicken of Tomorrow contest, organized by the USDA, with the backing of A&P and the support of every major poultry and egg organization in the country, all aimed at breeding a better chicken.

The effort was massive. The contest had 55 national organizers—scientists and bureaucrats loaned from government agencies, producer organizations, and land-grant colleges—and hundreds of volunteers in 44 states. (That was out of 48; Alaska and Hawaii had not been added yet.) It began with state contests in 1946, progressed to regional judging in 1947, and ended with a national competition, held at the University of Delaware’s Agricultural Experiment Station, in 1948.

View Images Eggs are produced at a conventional battery-cage facility in Lancaster County, Penn., an agricultural region where poultry farming has been on the uptick to meet growing demand from consumers—with a caveat. Consumers are pushing for eggs made in more humane conditions, through cage-free or free-range chickens, and to halt the use of antibiotics in broiler chickens. Photograph by Christopher Lamarca, Redux

What they aimed to achieve was droolingly described in the Saturday Evening Post in 1947, after the contest was two-thirds through: “one bird chunky enough for the whole family—a chicken with breast meat so thick you can carve it into steaks, with drumsticks that contain a minimum of bone buried in layers of juicy dark meat, all costing less instead of more.” Anyone who wanted to compete—and they ranged from small farmers to large, established companies—was granted one year to devise and breed a bird that possessed the sturdy, meaty qualities the contest was hoping for. If they reached that goal, they then had to prove their bird was reproducible, by breeding enough birds in enough generations to last through a three-year beauty pageant.

This was a significant challenge. Creating better poultry varieties had been a goal for decades, but maintaining reliable crosses had been challenging. Farmers distrusted crosses, worrying they would be sickly and not breed true, so most of the aspirants to the Chicken of Tomorrow contest competed by tuning up pure breeds that they were already raising. In the final stage of the contest, only eight of the 40 contestants entered birds crossbred from the historic standard breeds.

By March 1948, all 40 breeders, plus six more in case any were eliminated, shipped 720 eggs each to a hatchery on Maryland’s Eastern Shore. The shipments came from 25 states and were loaded onto trains according to a precise timetable so that each arrived at the right hour to go into incubators. The batches were coded so that only a few people knew their identity and put into one hatching pen per breeder, dark chickens next to white in case any got loose and tumbled into the pen next door. Once the eggs hatched, 410 chicks—400 for judging and 10 extra in case any came to harm—were picked at random from each batch of 500 and driven to new purpose-built barns.

View Images About 80 percent of antibiotics sold in the U.S. are used in livestock. The practice dates back to the 1950s, when it was discovered that feed laced with antibiotics allowed chickens to grow twice as fast, creating an industry. With the rise of antibiotic-resistant disease, consumers have been lobbying producers to remove the drugs from farming. Photograph by Erika Larsen, Redux

The chicks were allowed to grow for 12 weeks and two days and then were killed, defeathered, weighed, and chilled, as if they were going to be sold. Out of each breeder’s batch, 50 were picked for judging. That meant the judges were looking at 2,000 birds, and evaluating each of them on 18 criteria, from body structure and skin color to how early they had developed feathers and how efficiently they converted feed to muscle.

On June 24, 1948, the judges announced their results, on a stage adorned with boxes of chicken carcasses from each of the contestant’s batches, and frozen cross-sections of the top-scoring birds. The first runner-up was Henry Saglio, the teenage son of Italian immigrant farmers in Connecticut, who had bred his family’s pure line of White Plymouth Rocks into a muscular, meaty bird. The winner was Charles Vantress from California, who had crafted a red-feathered hybrid out of the New Hampshire, the most popular meat bird among East Coast growers, and a California strain of Cornish.

That evening, the contest celebrated the breeders’ achievements with a parade through Georgetown, Delaware, with floats depicting the phases of Delmarva’s poultry industry and a smiling, waving Festival Broiler Queen perched on top of a car. It celebrated not just the new birds but the new economy their developers hoped to create: a time when the Chicken of Tomorrow would be the dominant meat on farms and in markets, cheaper than beef, more docile than hogs, desired on its own behalf and not as a cast-off carcass after egg laying.

A second version of the contest three years later brought that day closer: Vantress won again, with another crossbreed, once again displacing a purebred bird. He would go on to establish one of the industry’s top hatchery companies, rivaled only by Saglio’s family company, Arbor Acres, which abandoned its winning purebred White Rock for a hybridized broiler in 1959. That same year, Vantress hybrids served as the sires of 60 percent of broilers across the country. The sturdy, free-living, weather-tolerant purebreds that had dominated American barnyards for almost 100 years vanished from commercial use.

The winners of the Chicken of Tomorrow contests did more than create new birds; when they transformed chickens, they recreated the chicken industry too. The earliest attempts at hybrids had been single crosses between two breeds: mother from one variety, father from another. But to ensure they could reliably reproduce the characteristics on which they were building businesses, breeders turned to creating complex crosses.

The intricacy of the family trees they constructed ensured that the birds could not be reproduced outside the companies that bred them. If a farmer who bought the new hybrids tried to mate them on his own property, the birds would not breed true. Previously, broiler farmers had bought chicks from hatcheries mostly for efficiency, but now they had no option.

Raising hybrid birds became like growing hybrid soybeans or corn: It required returning to the company to start each new crop. In a remarkably short span of time, the open-source birds that had populated millions of farm yards and back gardens for thousands of years became an ingredient in proprietary intellectual property. Simply by the mechanics of genetics, without even the assistance of patents, the patrimony of purebreds vanished behind the restrictions of trade secrets.

View Images At the Rodale Institute farm in Emmaus, Penn., hens have regular access to pasture, allowing them to graze and move freely outdoors. Founded in 1947 by an organic-gardening pioneer, the institute says pasturing promotes not only healthy chickens but also soil fertility and curtails crop pests. Photograph by Christopher Lamarca, Redux

National Geographic’s David Brindley talked to McKenna about how today’s chicken breeds may resemble yesteryear’s.

How did you dig up the Chicken of Tomorrow contest, and what was its role in telling the story of “big chicken”?

McKenna: What started me on the odyssey to produce this book was learning about the amount of antibiotics used in livestock around the world. I eventually concluded that the routine use of antibiotics created modern livestock agriculture. But use of antibiotics alone couldn’t account for the drastic changes in the bodies of chickens—the fact that the chickens we eat today grow twice as fast and twice as large as pre-industrial chickens. So I searched for how we ended up with the chicken of today.

The varied backyard and farmyard breeds of yesteryear all became one predictable hybrid: mild-mannered, white-feathered, big-breasted. How did that hybridization begin? I was expecting to find one scientist who sparked off something. Instead, I found out that it was a deliberate effort by the government—the USDA—and industry to literally change the shape of chicken through this contest.

What was the impetus for the contest back then?

The industry wanted to sell more chicken. Before this, the meat wasn’t so easy to eat or cook. It took a lot of effort to cook a chicken for essentially just one meal. The goal was to make chicken more desirable. The contest signaled that the supply of chicken meat had gotten out in front of demand. They wanted to stimulate demand by creating a more desirable chicken.

Are there any lessons from the contest we can learn from today?

As we start to talk about lab-grown meat, there’s a valuable lesson here. Chicken breeds became intellectual property—a genetic cocktail that today is owned by only two companies in the world. I find it troubling that the same thing has happened with lab-grown meat—it’s becoming intellectual property.

If there were a Chicken of Tomorrow contest held today, what would we be looking for?

I think we’d go back to the chicken of yesteryear. Probably not back to the 1800s, when chicken varieties were defined, but to the breeds of birds that have some of the characteristics that the industry is beginning to want again. Producers and consumers today are coming to reject extreme hybridization and “giganticization”—making chicken bigger and bigger. Producers have pushed chickens to the point where they can’t stand up on their own. They can’t get bigger. They are most likely in pain. The meat also isn’t as good as it was before. There is now what’s called woody breast syndrome, where the muscles in the breast become hardened, and also white striping in breast meat, a muscle disorder. All of those are expressions of how we made chickens grow too fast and pushed them beyond their genetic abilities. So now producers are pushing the clock back on hybridization. Chickens are now being bred to eat slower and grow slower. They have more energy and move around more.

What’s helping drive that change?

The Global Animal Partnership certifies ways in which meat is produced for retailers and wholesalers. In 2016 they proposed a ”higher welfare chicken” initiative that moves toward replacing current chickens with slower-growing ones by 2024, adding a couple of weeks onto a chicken’s life. That doesn’t seem like much, but it is when you consider that we only allow chickens to live to about 42 days. The initiative also requires more space, natural light, and opportunities to exercise—a more humane system for birds to be raised in industrial settings. Large-scale sellers, such as Whole Foods Market and major food service companies, have agreed to these principles.

A major theme of your book is the peril of antibiotic-resistant strains of bacteria. It’s a positively terrifying problem—and seemingly overwhelming. Is there anything individuals can do?

Consumers have more power than they realize. Chicken production changed because consumers showed the industry that if it changed its practices, there was a market waiting on the other side. The story of the emergence of the chicken we eat every day really brackets the use of antibiotics in industrial farming. The first use of antibiotics in livestock agriculture was on chickens. And now chicken producers are going antibiotic free. Perdue announced it in 2014. I reported that story for this book, and Perdue told me they were getting 3,000 customer comments a month asking why they weren’t antibiotic free. That was a strong enough signal of consumers wanting something different. And it’s important to note, it’s not as though those 3,000 people arranged to do that together. But the collective power of the actions of individuals gives me hope, and that’s one of the reasons I wanted to write this book. This was a story in which solutions are expressing themselves. This was a moment of achievement, of changing part of the food system.

This interview was edited for length and clarity.