What Came First, the Chicken or the Egg?

The question-what came first, the chicken or the egg? – is an old riddle that has bamboozled the old and the young for many generations. It sounds like a simple question.

However, if the chicken egg came first, one would ask who laid the egg. Similarly, if a chicken came first, where did the egg come from since all birds, including chickens, come from eggs?

Thankfully, we don’t have to spend years brooding over this question. We can use scientific tools and historical evidence to unscramble this riddle.

The Arguments for the Chicken

Some suggest that chickens precede eggs, ultimately making them believe chickens came first, not the eggs. Well, let’s see some of the arguments that chickens came first.

Historical Evidence of Chickens Preceding Eggs

Scientists note that the first chicken on the planet was due to genetic mutations in the zygote from two proto-chickens. The zygote was a result of the two proto-chickens mating and combining their DNAs to create the cell of the world’s first chicken.

Genetic mutations have occurred since then, with the mutations copying themselves into all the body cells as the chicken zygote grows. The result of these mutations was the first real chicken.

Historical evidence also shows that the parents of the first real chicken were male and female red junglefowl. These two birds are native to southeastern Asia.

Archeological evidence shows that humans’ domestication of the red junglefowl took place in Malaysia, Indonesia, and China around 10,000 years ago. These chickens became widespread due to their popularity as prolific layers and less-aggressive chickens.

Mathematical simulations and DNA analysis suggest that today’s domestic chickens are descendants of the wild red junglefowl.

Reproduction of Chickens

Chickens have an intricate reproduction system, unlike other animals. For instance, roosters don’t have penises like other male creatures. Roosters have small openings near their vent areas, which they use to emit sperm into hens. Furthermore, roosters’ testes are within their bodies.

Hens’ reproductive systems have different parts. Every hen has two ovaries, although only one ovary is functional. The average hen has between 3500 and 4000 ova (eggs) inside her ovary. A follicle holds the ovary to the reproductive tract.

A hen also has a funnel along its reproductive tract, where fertilization occurs. During mating, the cock’s vent area and the hen’s cloaca touch each other, and the cock dispels sperms into the hen’s cloaca, which sucks the sperms into the oviduct and ultimately fertilizes the eggs.

However, it’s prudent to note that egg formation in hens doesn’t depend on fertilization. Egg formation will occur regardless of whether fertilization occurs because fertilization and egg formation are two different processes.

Chicken Genetics

Chromosomes determine the gender of an offspring in all creatures. In humans, for instance, the chromosomes that determine the gender of a baby are the X and Y chromosomes. XX chromosomes indicate a female gender, while XY chromosomes indicate a male gender.

In chickens, the sex chromosomes are W, and Z. ZW means that a chicken is a hen, while ZZ shows that a hen is a rooster. The Z chromosome is much longer than the female W chromosome.

Furthermore, the Z chromosome has more information than the female W chromosome. Hens have a single copy of several genes because they exist strictly on their z chromosome.

That’s why understanding the chromosomal differences and sex-linked traits is vital for anyone breeding chickens.

Like humans, chickens also have DNA containing information about their ancestors. However, the information is different from their ancestors. Every living creature has a mix of DNA from its parents.

Chickens get around 50%of DNA from each of their parent. Nonetheless, the amount of DNA chickens get from their ancestors declines over time.

The Arguments for the Egg

Some people believe that the egg came before the chickens, while others believe that the egg came first.

After all, they claim to have historical data for eggs preceding chicks.

Historical Evidence For Eggs Preceding Chicks

The oldest embryos and dinosaur eggs are around 200 million years old. Furthermore, archaeopteryx fossils show that birds have existed for close to 150 million years, meaning all birds, like chickens, came after the eggs.

That observation may be accurate when you think about chickens and the eggs they emerged from. Some scientists also believe that some creature resembling a chicken laid an egg containing a genetic makeup similar to a true chicken.

Archeological evidence also shows that chickens, like other birds, came from reptiles. Thus, it’s genuine to suggest that the first chicken hatched from an egg laid by an unknown reptile, similar to a chicken.

The reptile also emerged from an egg. Most importantly, chickens are multicellular animals that produce eggs. Egg-laying takes center stage in vertebrates’ history. Of all the creatures, it’s only mammals that give live births.

All the other animals lay eggs. Similarly, hens make eggs and carry them in their bodies until they lay them after the egg formation process.

Biology of Egg Production

Egg production in chickens starts with oogenesis, the process where a chicken’s ovary produces eggs. The process involves many sequential stages where chickens initiate egg production and pass out eggs from their bodies.

The most considerable involvement by hens in the process of egg formation is making eggshells. Your hens will spend significant time ensuring they make solid and calcium-rich shells.

The egg formation process usually starts at night when your hens are asleep. Hens start laying at maturity, but their egg production rates gradually decline as they age.

Hens undergo the ovulation process to initiate the process of egg production. Ovulation in eggs occurs when a hen release a yolk from her ovary. The process occurs around 24 to 26 hours, irrespective of whether fertilization occurred.

It takes a hen around 26 hours to release a yolk from her ovary after laying the last egg. As the yolk from the ovary enters a hen’s magnum, it goes through layers of thin and thick proteins.

These layers are known as albumens and help make the egg white. Hens usually lay in the early daytime hours after completing the egg production process at night.

Anatomy of Egg

It’s essential for anyone raising chickens to comprehend the anatomy of the chicken egg.

The average chicken egg consists of eight different parts. Below is a comprehensive look into the different parts of a chicken egg.

  • Shell– The shell is the external layer of a chicken egg comprising calcium carbonate. It contains thousands of tiny pores which enable moisture to go through the eggs.
  • The outer and inner membrane-An egg has an outer and inner membrane to keep off bacteria from entering the egg.
  • Air cell-The air cell on a chicken egg sits between the outer and inner membranes. The air cell helps keep the egg at a stable temperature.
  • Albumen– The albumen is egg white and consists of different types of proteins.
  • Yolk- the egg yolk contains multiple minerals and vitamins
  • Vitelline membrane-The vitelline membrane is the casing enclosing the yolk.
  • Chalazae– This part works as the yolk’s anchor, keeping the yolk in the middle of the egg.

Popular Culture Around the Debate

From ancient history to modern times, they have been popular culture around the debate –what came first, the chicken or the egg? The debate has been a crucial symbol in several cultures worldwide.

In Greek culture, for instance, the debate symbolizes renewal, rebirth, and life. The argument is also vital since it reflects on the creation of chickens, taking us back to the evolutionary era when there was no single chicken on the planet.


It’s easy to assume that the egg came first because archeological evidence shows eggs have been around for millions of years.

However, some people remain adamant that chickens came first because, without these birds, there could be no eggs.

If you look at this debate, it will help you reflect on the genesis of the modern chickens we raise today.

avatar James
Hey, I'm James, a hardworking homesteader for more than 30 years. I enjoy the feeling of accomplishment that comes from tending my flock. I've raised chickens and ducks for eggs and meat for many years. I also have experience with other poultry too. Learn more

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