Which came first, the chicken or the egg? Scientists settle the debate

by · Mail Online

Since the dawn of humanity, there is one question that has scrambled the minds of history's greatest thinkers. 

That question is: 'Which came first, the chicken or the egg?'

This World Egg Day, MailOnline has asked evolution experts for their views on this classic conundrum.

They argue that although eggs evolved millions of years before the chicken, this doesn't necessarily mean the egg came first.

So, do you think these egg-heads have cracked this ancient puzzle?

Which came first, the chicken or the egg? This question has been puzzling great minds since the dawn of humanity but now MailOnline has asked the experts to solve this case once and for all (stock image)

Which came first, the chicken or the egg?

If the question is simply whether chickens or eggs evolved first, the answer is certainly eggs.

The first eggs of any kind evolved about 600 million years ago.

The first hard-shelled eggs followed about 195 million years ago.

Even the first bird eggs date back 120 million years.

Chickens, meanwhile, only emerged 3,000 years ago.

However, the first specimen of the domestic chicken would have been born to chicken-jungle fowl hybrid parents.

This means the first chicken came before the first chicken egg.  

What is an egg?

Eggs have existed for almost as long as all life on Earth.

And other than mammals, almost every type of animal lays them.  

Jules Howard, zoology correspondent and author of a book on the evolution of eggs titled 'Infinite Life', told MailOnline: 'Eggs are the "go-to" way for evolution to send genetic lines forwards in time.'

The evolution of the first eggs may be intimately tied to the birth of life as we know it.  

Mr Howard says: 'Eggs are vessels in which sperm and egg can mix to create a new, novel combination of genes that becomes the adult form.' 

Before this evolutionary development, organisms reproduced through a form of cloning - producing a genetically identical population which was very vulnerable to viruses and parasites.

By creating a place for sexual reproduction to take place, Mr Howard argues that eggs allowed for the creation of species made up of unique individuals.

'Without sex, and by extension eggs, we think it's likely that individuals become ravaged by viruses meaning they more often die out,' says Mr Howard.

The first eggs would have very different to what we would recognise as an egg today and would have been laid by jellyfish or worm-like creatures from the dawn of time.

Chickens are far from the only species to lay eggs although the form and function vary from hard-shelled bird eggs to the 'mermaid's purses' (pictured) from which sharks hatch
At the most basic level, an egg is just 'a life-support capsule' for a young animal providing it with everything it needs to grow while being protected from the outside world 

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Dino-mite find! Scientists discover more than 250 fossilised titanosaur EGGS in India - suggesting dinosaurs nested together, just like modern birds

Mr Howard explains: '600 million years ago, fossils from China suggest the eggs were tiny – not much thicker than a human hair.

'These were eggs that blew through oceans, as if in milky clouds. There were no nests. These eggs were pumped into the water and came to rest on the seafloor.'

If we accept that an egg is just a 'life-support capsule' for an animal then these would surely count as eggs of some form.

Given that this was hundreds of millions of years before life even ventured onto land, it seems safe to say that the egg came before the chicken. 

For the majority of us who think of eggs as hard-shelled things that can be cracked open, this might not be a very satisfying answer. 

Unfortunately for anyone who still had their money on the chicken, the first hard-shelled eggs still emerged much earlier.

Scientists believe that the first eggs would have been laid by the ancient relatives of jellyfish such as the moon jellyfish (pictured) which existed 600 million years ago 

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Dr Ellen Mather, a palaeontologist from Flinders University who specialises in ancient birds, told MailOnline: 'If you frame it as referring to eggs as a whole, then the answer is most definitely eggs.'

What is a chicken?  

The first domestic chickens descended from a species of red jungle fowl called Gallus gallus which evolved around 50 million years ago.

Researchers believe that as humans started clearing areas of forest to cultivate rice and millet, birds from the jungle began to gather at the edges of the new fields. 

Over time, as the birds adapted to their new neighbours they became more accustomed to humans, less territorial, and started raising larger broods of chicks.

Domesticated chickens were bred from wild red jungle fowl which gathered at the edge of newly cleared farmland 

Eventually, this transformed some of the wild jungle fowl into a new species which became known as chickens or Gallus gallus domesticus.

Previously, researchers believed that the first true domestic chickens had emerged around 10,000 years ago.

However, subsequent analysis reveals that many of the supposed 'chicken' specimens actually belonged to other wild birds such as ducks.

More recent studies suggests that humans in Southeast Asia first domesticated these birds somewhere between 1650 BC and 1250 BC.

At most, that would make the chicken around 3,500 years old.

This map shows the earliest dates chickens have been found around the world in years ago. Scientists believe that the first chickens emerged in Southeast Asia just under three thousand years ago

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What came first, the T.Rex or the egg? 

While chickens are only a few thousand years old, the egg, on the other hand, dates back millions of years to the time of the dinosaurs.

Dr Mather says: 'The first eggs laid on land would have come much later during the Carboniferous between 358 to 298 million years ago, laid by early reptiles.'

Those eggs were most likely soft-shelled like the eggs of modern reptiles such as snakes.

Dr Mathers says that the first hard-shelled eggs emerged during the Early Jurassic period and were laid by dinosaurs.

Fossilised eggs laid by the long-necked sauropods - the family which includes the Brontosaurus and Diplodocus - have been found dating back 195 million years. 

Hard-shelled eggs first emerged around 195 million years ago in the Early Jurassic period. Scientists have even found dinosaur embryos preserved within their eggs in positions which resemble modern-day chickens 

These would have looked a lot more like the eggs we would recognise from many birds and lizards today.

Last year, scientists even found a vast dinosaur hatchery containing 91 titanosaur nests and 256 eggs, showing that these giant creatures nested together just like birds.

Even if we limit our search for eggs to just those laid by birds, the chicken still loses by more than 100 million years.

Archaeopteryx, the first bird to evolve from the dinosaurs, appeared around 150 million years ago.

Likewise, the oldest confirmed fossil egg believed to have been laid by a bird is roughly 127 million years old, dating back to the Early Cretaceous.

So, in any evolutionary terms, the egg definitely came before the chicken.

Fossilised eggs belonging to sauropods (pictured) were laid in nests and had hard shells many million years before the first chickens emerged 
The first bird, the Archaeopteryx, evolved 150 million years ago and scientists have discovered fossilised bird eggs dating back 127 million years 

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Egg-cellent find! Roman chicken egg discovered in Aylesbury still has its yolk and whites intact after 1,700 YEARS, scans confirm

The case for the chicken  

While that might seem like a knockdown blow for the chicken, this is only one way of interpreting the question. 

'Depending on how you interpret the question, both answers could be correct,' says Dr Mather. 

Instead of asking whether chickens or eggs evolved first, a more classic version of the question is to ask whether the chicken or the chicken egg came first. 

The obvious puzzle is that we might think a chicken can only be hatched from a chicken egg which, naturally, can only be laid by another chicken. 

Aristotle, one of the first thinkers to grapple with the chicken vs egg debate, saw it as an example of infinite regress - chickens hatching from eggs which were laid by chickens all the way backwards through time.

The Greek philosopher Aristotle was one of the first to ponder the chicken vs egg question. He believed that this was a case of infinite regress since a bird must have come from a bird egg which, in turn, must have been laid by a bird 
With our modern understanding of evolution, we know that there would have been a first chicken born to junglefowl parents. So, in a sense, the chicken did come before the egg (stock image) 

However, thanks to our modern understanding of evolution, we know this isn't the case.

Species like chickens aren't unchanging blocks that exist for all time but temporary structures thrown together by churning evolutionary currents.

This means there would have been a moment at which a population of wild birds stopped being jungle fowl and started being chickens.

Dr Mather says: 'The first true chickens would have hatched from eggs laid by partially domesticated red jungle fowl.'

In other words, the first true chicken would have hatched before any true chicken eggs were laid. 

Dr Mathers concludes: 'If the question is interpreted as referring to chicken eggs, then the answer would be a chicken.'