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What Did Chickens Evolve From?

The modern day chicken comes in many shapes and sizes and colors. As chickens become more and more popular as a backyard pet, and as more breeds and hybrids are introduced, you may start to wonder, “How did we get here?” Fascinatingly, the modern chicken has come a long way — when speaking of its evolution. Today’s domestic chicken (Gallus gallus domesticus) can be traced back to its wild ancestors, the Southeast Asian Red Junglefowl (Gallus gallus) and other related species. Recent DNA studies have shed light on the complex genetic lineage of chickens, revealing hybridization with other junglefowl species.

In other words, chickens are more than just modern day dinosaurs. They have a history as complex as the evolution of humanity. Fitting for birds who have been raised by people for centuries!

So without further ado, let’s answer the question, “What did chickens evolve from?”

From Dinosaurs to Domestication — A Long Process

Chicken evolution

The evolutionary lineage of chickens can be traced back to a group of dinosaurs known as theropods. Around 230 million years ago, these theropods split into two categories: Ceratosauria and Tetanurae. From the Tetanurae category emerged the genetic line that eventually led to the Tyrannosaurus rex. In 2003, paleontologist Jack Horner made a remarkable discovery when he found a 68 million-year-old T. rex fossil in Montana. Genetic analysis of the fossil revealed an astonishing revelation: chickens are the closest living relatives of the mighty T. rex. This finding highlights the surprising evolutionary connection between these seemingly disparate creatures.

Does that mean that chickens evolved directly from dinosaurs? Well, not necessarily.

Somewhere along the line, the predecessor of the modern chicken diverged from the Jurassic path. Science is still attempting to knit together the details. So, let’s fast-forward to a slightly more recent history.

50 Million Years Ago

red junglefowl (male)
Red Junglefowl

Chickens come from various species of wild junglefowl that inhabited Southeast Asia around 50 million years ago. Yes, you read that correctly. The Red Junglefowl (Gallus gallus) from back then is thought to be the primary progenitor of the domestic chicken, although genetic studies suggest hybridization events with other junglefowl species. These hybridizations have contributed to the genetic diversity and unique traits found in different breeds of domestic chickens.

This is also why European breeds look slightly different from those that have been bred for centuries in other parts of the world. 

Chicken or Egg: What Came First?

Eggs were around way before chickens even existed.

The age-old question of which came first, the chicken or the egg, has intrigued many. From a biological standpoint, the answer lies in the existence of eggs predating chickens. Fossils of dinosaur eggs and embryos date back approximately 190 million years, while the oldest accepted bird fossils, such as Archaeopteryx, are around 150 million years old. Thus, eggs came before chickens in the evolutionary timeline.

When you think in terms of evolution, this makes sense. Modern day chickens now have standard features that would once be considered genetic mutations, and these probably first became visible over a millennia ago!

Human Influences on Chickens

So, if the granddaddies of chickens have been around for millions of years, when exactly did they become the chickens we know today? Although it is difficult to pinpoint the exact moment, it is believed that the domestication of chickens that began around 8,000 to 10,000 years ago played a significant role. Chicken-human interactions first began in Asia and India. The process of domestication was likely driven by multiple factors, including the availability of food, cockfighting, and religious practices.

Archaeological and genetic studies have also shed light on the origins of chickens, with China playing a prominent role. In 2018, a study conducted by a Chinese bioanthropologist examined 280 bird bones dating back to the Neolithic and Bronze Ages. These bones were identified as chickens, providing evidence of their presence in ancient China.

However, the question of whether chickens were domesticated in China or imported from southern China or Southeast Asia remains a subject of debate. German archaeologist Joris Peters and his colleagues, in 2016, analyzed environmental proxies and other research and argued that the habitats suitable for jungle fowl, the wild ancestor of chickens, did not exist early enough in China to support domestication. They propose that chickens were a rarity in Northern and Central China and were likely introduced from regions where evidence of domestication is more substantial, such as southern China or Southeast Asia.

Yet, the where does not seem to matter, because chickens are now seen throughout the world. As chickens became more domesticated, they began accompanying humans on migrations, trade routes, and territorial expansions, eventually spreading across the globe. For example, Polynesians are credited with introducing chickens to South America around 1200 AD, while Spanish explorers brought flocks to North America.

Junglefowl Genetics and Chicken Evolution

Distribution of the four junglefowl species

Remember the Red Junglefowl mentioned earlier? DNA studies have found that Gallus gallus is not the sole progenitor of the modern chicken. The Grey Junglefowl (Gallus sonneratii) is believed to have contributed the gene for yellow skin and shanks. This hybridization event likely occurred at some point during the domestication process. Evidence of this influence can be seen in physical characteristics found in breeds like the Indian Gamebird (Cornish) and the Brahmas of China.

Other junglefowl species have also made contributions. The Sri Lanka Junglefowl (Gallus lafayetti) has left its mark in the tail carriage of the Sumatra breed, while the Green Junglefowl (Gallus varius) is thought to have had an impact on modern chickens.

Chickens of Today

Today, there is a wide variety of chicken breeds, each serving a specific purpose. While there are breeds suited for meat production, chickens are primarily raised for egg production. Selective breeding has led to the development of breeds with specific physical traits that optimize egg-laying capabilities.

Over generations of selective breeding, specific physical traits were honed to create diverse breeds of chickens. A significant milestone in this process occurred in 1874 when the American Poultry Association introduced the first Standard of Excellence, marking the advent of the “Golden Age of Pure Breeding.” This development paved the way for advancements in poultry and influenced the breeding practices of other livestock species.

Notably, researchers discovered a correlation between earlobe color and egg shell color. Breeds with white earlobes tend to lay white eggs, while those with red earlobes often produce brown eggs. This fascinating connection provided insights into the genetic factors influencing eggshell pigmentation.

Chickens breeds are categorized into three main groups: heavy breeds, light breeds, and dual-purpose breeds. The heavy breeds, such as the majestic Brahma, mature slowly and gradually. While not particularly known for their egg-laying capabilities, these breeds excel in other areas.

On the other hand, light breeds, including breeds like Minorca, Leghorn, and Ancona, prove excellent as broilers and prolific egg producers. Their efficiency in egg production has made them popular choices among poultry enthusiasts.

Finally, the dual-purpose breeds serve a versatile role, being raised for both egg and meat production. Notable examples of dual-purpose breeds include Rhode Island Red, Barred Rock, and Wyandotte. These breeds strike a balance between egg production and meat yield, making them valuable additions to poultry farming.

Finally, you can watch this video where a museum scientist talks about the origin of the chicken:

Final Thoughts on Chicken Evolution

What did chickens evolve from? You could say the dinosaurs, and that would be correct, but the modern day chicken is most closely linked to various junglefowl in Southeast Asia. From their origins in Southeast Asia to their worldwide dispersal through human migrations and explorations, chickens have become an integral part of human culture and culinary practices. Today, a myriad of chicken breeds exists, each with its own unique traits and purposes. As we enjoy the eggs provided by these remarkable creatures, let us appreciate the extensive history and remarkable genetic heritage that brought them to our backyard coops!