Which Came First, the Chicken or the Egg? New Study Reveals an Answer

“What came first, the chicken or the egg?” This classic debate has raged on for centuries baffling philosophers, scientists, and curious minds for centuries. Is there any logical answer to such a question comparable only to the mystery of the creation of the universe? In collaboration with Nanjing University in China, scientific minds at the University of Bristol have come together with a compelling answer. Rooted in evolution, biology, and zoology, the question can be broken down by exploring the evolution of birds, their ancestors, and the role of eggs in the animal kingdom.

The Origins of Eggs in Evolution

Fossil evidence suggests that eggs, particularly hard-shelled ones, appeared around 195 million years ago, long before chickens existed. Early reptiles, amphibians, and some fish laid eggs, a critical adaptation that allowed animals to reproduce outside water. This evolutionary innovation laid the groundwork for what would eventually become the modern chicken egg.

The Chicken’s Evolutionary Path

Chickens are domesticated descendants of wild birds, specifically the red junglefowl. Evolutionary biologists have traced their origins through natural selection and hybridization over thousands of years. This development involves genes being passed through generations, each laying eggs that incubate the next generation of birds. This concept has led some scientists to believe that prehistoric ancestors of modern-day birds laid eggs, which is why the egg came first. Then, some feel the chicken popped out of the evolutionary blue and laid an egg.

The New Study

In collaboration with Nanjing University in China, research from the University of Bristol studied 51 fossil species and 29 living species. They split the specimens into two categories: oviparous, those who laid shelled eggs, and viviparous, those who gave birth to live young.

The study published in Nature Ecology & Evolution found how some early reptiles, the ancestors of modern birds, did not lay eggs but gave birth to live young. This challenges the common belief that all ancient birds or reptiles reproduced via eggs. The shift to egg-laying evolved for various reasons, including the protection and development of embryos.

The Evolutionary Step Towards Modern Birds

The new research suggests that early animals retained embryos for extended periods, making live births safer than laying eggs. Professor Michael Benton of the University of Bristol explains that early tetrapods, initially amphibious, evolved into amniotes around 320 million years ago. Amniotes developed features like waterproof skin and the amniotic egg, which allowed them to break away from water-dependent breeding, marking a significant evolutionary step toward modern birds.

Preceding The New Study, Scientists Believed It Was the Egg

One critical factor that led to the modern chicken was the discovery of a protein called ovocleidin-17 (OC-17), which is essential for forming eggshells. This protein is produced in the ovaries of hens, suggesting that while eggs existed long before chickens, chicken-specific eggs, as we know them today, came after the development of chickens.  

This conclusion is that egg-laying species existed long before chickens, and genetics might have caused jungle fowl to reproduce mutations through natural selection. These mutations might have led to the first chicken emerging from an egg laid by a non-chicken ancestor. Thus, according to one section of scientists, the egg predates the chicken.

The New Study Says the Chicken Came First

Professor Michael Benton notes that recent research has challenged the traditional view of reptile eggs. Biologists, including project leader Professor Baoyu Jiang, have found that many reptiles, like lizards and snakes, can switch between laying eggs (oviparity) and live birth (viviparity) more flexibly than previously thought. This research suggests that egg-laying isn’t as rigidly fixed, and live-bearing animals may revert to laying eggs more easily. The new findings add a layer of complexity to the debate, potentially supporting the idea that the chicken came first.

What do you think is the question answered? Or is there still room for debate is it the chicken or the egg?