Beginning in Mesopotamia and Ancient Egypt more than 5,000 years ago, humans have used science as a way to ask questions about the world. And the pursuit of science has not been restricted to this planet – it extends into the deepest regions of space. In 2019, in fact, scientists were even able to photograph a black hole.
But along with the soaring mysteries of the universe, scientists also ponder the more mundane puzzles. Among the many questions that have gained the attention of the men and women of science over the years is a simple, yet taxing, one. That query is: which came first, the chicken or the egg?
That question may seem a paltry one, barely worth thinking about. However, philosopher Roy Sorensen explained to Time magazine in September 2016 that it was more significant than it first seemed. He said, “It’s a charming problem because you want to dismiss it as a stupid question. You can see on reflection that we’re impatient with it, but it’s not a stupid question.
Indeed, Smithsonian magazine even felt able to declare the problem solved in 2013. But was the publication’s confidence merited? And what was the answer that it believed so strongly in? To seek out the truth, we will begin our journey in the Asian tropics, where our ancestors found the red junglefowl.
It’s not certain when the red junglefowl was tamed, but evidence from archaeology suggests it may have been as many as 10,000 years ago. However, studying chicken DNA has led researchers to suggest the two species diverged nearly 50,000 years before that. Either way, the chicken has been a ubiquitous part of human life for many thousands of years.
Our forebears, however, didn’t originally keep chickens for food. They instead used them in cockfights or rituals. It wasn’t until the fourth century B.C., in fact, that people began to chow down on their meat. Indeed, bones found at Maresha, an archaeological site in Israel, show signs of butchering, an indication that the fowl had been kept for meat.
The discovery marked a real change in human history. Suddenly, chicken became a desirable munchable all across the Roman Empire. An archaeologist who worked at the Maresha site, Lee Perry-Gal, told NPR in 2015 about how the foodstuff was a sensation. She said, “From this point on, we see a bigger and bigger percent of chicken. It’s like a new cellphone. We see it everywhere.”
It’s not certain why Maresha’s inhabitants began to eat chicken. It might be, though, that they discovered how to breed bigger birds and more of them, so that they became more alluring as a source of food. Perry-Gal thinks that the key lay in a social change of heart about the practice. She told NPR, “This is a matter of culture. You have to decide that you are eating chicken from now on.”
Certainly, chicken has become an extremely desirable foodstuff over the centuries. These days, it’s easily the most popular meat in the U.S. And it’s quickly catching up to pork world-wide. Believe it or not, for 2019 production looked set to approach 100 million metric tons, with the U.S. alone producing 19.5 million tons of the bird.
When chickens are kept for their meat, they have the name “broilers.” And while a hen can live upwards of six years if left to its own devices, most broilers have a somewhat shorter lifespan. They generally grow to the desired size within six weeks. Organic or free range birds, however, live a bit longer, up to about three months or so.
Those chickens kept mostly for their ability to provide eggs, though, have a much longer life. Hens can lay more than 300 eggs in a year, but they are only able to keep that up for a 12-month period. That’s unless the farmer starves them for a couple of weeks, in a process called “forced moulting,” which restarts vigorous laying.
The popularity of chickens has also made them a significant feature in human lives. This has prompted many thinkers to ponder which came of the chicken and egg pair started the whole thing off. The first notable chinscratcher to get stuck into this question was Aristotle, who considered it back in the days of Ancient Greece.
However, even Aristotle’s wisdom couldn’t find a satisfactory answer. He ducked the question by claiming that both the egg and the chicken had existed forever. Apparently, he asserted that if there was an egg, then a bird had to lay it. And that there bird, then, must have had an egg to pop out of in the first place.
Another Greek, Plutarch, was the next star thinker to take on what he called the “little question.” To begin with, he formed the question in the now familiar way: “Whether the Hen or the Egg Came First.” Then, he suggested that the puzzle even had a bearing on the “great and weighty problem” of the world’s beginning.
Macrobius, a fifth-century scholar of the Roman Empire, later picked up the philosophical baton. He didn’t think that the riddle was anything to joke about, concluding that “the point should be regarded as one of importance.” However, the roman doesn’t seem to have come to any firm conclusion about the answer.
With the rise of Christianity, however, the chicken and egg paradox posed a serious problem for theologians. Those such as St. Thomas Aquinas and Augustine pondered the issue at length. That’s because for them, the biblical answer seemed clear, but the Greek philosophers’ ambiguity conflicted with the certainty they found in Genesis.
Indeed, Genesis 1:21 says that God created “every winged bird according to its kind,” which seems to settle the matter. So, as birds were made with the inherent ability to lay eggs, the chicken must have come first. However, modern-day creationists claim the story doesn’t quite end there. They analyzed both the wording of the Bible along with the traits of chickens and other birds to arrive at a different conclusion.
Creationists believe that birds did not evolve from dinosaurs, but, instead, were created in “kinds.” They also think that God made sure those “kinds” included genetic diversity. These traits then passed from bird to hatchling, so it may be that a non-chicken laid a chicken egg. Consequently, their conclusion was that the egg actually came first.
Italian Ulysse Aldrovandi, however, didn’t bother with that sort of analysis. Indeed, he considered the issue completely settled in 1600. During that year, he wrote, “These books teach that animals were created at the beginning of the world; hence the hen did not come from the egg, but from nothing.” However, not everyone agreed.
One of those who demurred from Aldrovandi’s simple certainty was philosopher Denis Diderot. The 18th-century Frenchman was a prominent Enlightenment thinker. His book, Encyclopédie aimed, he wrote, “to change the way people think.” Indeed, he had his own idea about the paradox, and scoffed at the simplistic solutions of earlier thinkers.
In 1769 Diderot forcefully expressed his view of the puzzle. He wrote, “If the question of the priority of the egg over the chicken, or of the chicken over the egg embarrasses you, it is because you suppose that animals originally were what they are at present.” And he would leave his readers in no doubt how he felt about that. “What folly!” he continued.
And Diderot would later gain some support from one Charles Darwin. His 1859 work, On the Origin of Species, presented his theory of evolution. This emphasizes gradual change, which doesn’t allow a scientist to pinpoint when one species becomes another. With the shading of one type of creature into a different one, the truth is that they simply overlap.
However, one thing’s for sure: eggs did come before chickens. Fossil hunters have found dinosaur eggs that were probably laid about 190 million years ago. And as we will see, they’re not even the oldest of eggs on the planet. But are they the same kind as a chicken’s egg?
The University of Calgary’s Darla Zelenitsky confirmed that the eggs were indeed the same to Popular Science in 2013. She said, “A lot of the traits that we see in bird eggs evolved prior to birds in theropod dinosaurs.” The theropod group of prehistoric creatures included the fearsome Tyrannosaurus. And although scientists are certain T. rex laid eggs, none has ever been found.
Meanwhile, the earliest bird to evolve was Archaeopteryx. This first took to the air about 150 million years ago. And although it had some of the features of the modern bird, it still betrayed its dinosaur origin very strongly. Still, if we count it as a bird – and scientists do – it means avians came into being some time after eggs.
However, the type of bird’s eggs that we fry, scramble and poach today were not the first by any means. Long ago, most animals laid a form of eggs, but had to so do in wet environments. If left on land, the eggs would dry out. So reproduction had to happen in bodies of water of one sort or another.
These moisture-dependent eggs are still around today, of course, laid by amphibians and fish. These animals produce eggs that are like blobs of jelly and are fertilized in the water. They don’t have a shell, so they would quickly become dry in the open. Even frogs that live on land have eggs like this. Indeed, one of them, the Coast foam-nest treefrog, lays its eggs on terra firma, but with a covering of foam to keep them moist.
However, evolution found a cunning way to keep the inside of an egg moist. Millions of years before Archaeopteryx, a type of egg evolved that enclosed its contents in membranes. These “amniotic” eggs not only provided a safe environment for the embryo, but also allowed the inclusion of nutrients for sustenance. And, most importantly, they developed hard shells.
The four-legged animals that had evolved to produce amniotic eggs were then able to do something that had previously been impossible. About 300 million years ago, these amniotes started to lay eggs on land. And although today most animals, including humans, are amniotes, the first to bear the name looked like little lizards.
Those lizards had eggs with a feature that is still common today: a big yolk. James R. Stewart, who works in reproductive physiology at East Tennessee State University, noted this to Popular Science in 2013. He said, “You still see that in birds, crocodilians and snakes.” But you won’t find it in humans – there’s no yolk in our eggs, although there is the vestige of a yolk sac.
Chicken eggs, of course, do have a large yolk. And, like other birds, hens have eggs with a hard shell. These days, though, they’re the only kind of animal that does. And although all avian species are considered a kind of dinosaur, and consequently a sort of reptile, modern-day reptiles tend to lay eggs that are leathery or chalky.
In contrast, most mammals do not, of course, lay eggs, although there are exceptions. The platypuses and spiny anteaters of Australia both do, just as some earlier species, which later went extinct, did. However, they do not have hard bird-like shells: platypuses produce leathery eggs that look similar to a reptile’s.
Outside of those Australian rarities, mammals do not lay eggs. But that doesn’t mean they don’t produce them. Scientist William Harvey asserted in the 1600s that every animal must come from an egg. And, of course, humans do, too. However, although the ovum is one of the body’s largest cells, it’s much smaller than a chicken egg at only a four-thousandths of an inch across.
So it’s official. Eggs came before chickens – and by many millions of years! But what about the actual egg that chickens lay today? Well, it seems that the answer to the age-old paradox remains the same. The egg came before the chicken, and the reason why is a simple matter of evolution.
In the gradual move from something that wasn’t a chicken to something that definitely was, there must have been a time where a very-nearly-chicken laid an egg containing a full-on chicken. The DNA of that almost-chicken, then, would have held the mutation that brought about the bird we recognize today. But we will likely never identify exactly when that occurred.
Indeed, world-renowned astrophysicist Neil deGrasse Tyson confirmed this answer on Twitter in 2013. He wrote, “Just to settle [this] once and for all. Which came first, the chicken or the Egg? The egg – laid by a bird that was not a chicken.” And his decisive claim was backed up by the voice of science.
Yes, TV’s Bill Nye the Science Guy explained the mechanism in a reply to Tyson. He tweeted, “[The] first such egg [was the] result of [a] proto-chicken and [a] proto-rooster hookin’ up. The parent organisms were not quite chickens. It’s evolution.” However, some other scientists found something that may call into question Nye’s certainty.
It turns out that a protein in a chicken’s ovary hastens production of eggshell. In fact, a chicken egg can’t be made at all if the protein is missing. So, did chickens actually come first? Lead study author, Sheffield University’s Colin Freeman, told CNN in 2010, “Obviously, it’s not really what we were trying to get out of our simulations. But it’s an interesting question isn’t it?” he said.
In a press release, the researchers who looked at the protein, ovocledidin-17, were less than definitive about the answer, though. They wrote, “Does this really prove the chicken came before the egg? Well, this actually further underlines that it’s a fun but pointless question.” The team felt their work had better uses than deciding the age-old paradox.
So after thousands of years thinking about the question, science has come up with an eggs-cellent answer. There’s little doubt that eggs came before chickens. However, if we’re talking about the actual egg that today’s hen lays, well… It seems that this one’s going to remain a rather hard-boiled paradox.