Did the chicken or the egg come first? I have the answer.
People often end up talking past each other because they don’t realize their disagreement is really about how they’re defining different words.
It’s a classic conundrum: which came first, the chicken or the egg? And it turns out… that this question is really easy to answer. Dinosaur eggs existed for millions of years before chickens ever did, and fish were laying eggs for millions of years before that. The egg came first, case closed, end of story.
But here’s a better question: which came first, the chick or the chicken egg? This question is a lot harder, because it ends up being an issue of drawing category boundaries. What even is a chicken, anyway? It’s a question of semantics, which makes it a lot more subjective than you would expect.
Modern chickens descended from a bird called the red junglefowl (gallus gallus) that lives in southeast Asia. It was also brought to the Hawaiian islands by Polynesian settlers, and you can still find a bunch of them all over the islands (see my picture below). Domestic chickens (gallus gallus domesticus) are considered to be a subspecies of red junglefowl. And that’s the problem: what the heck is a subspecies?
Some chickens I saw walking around in Hawaii. The Merlin app identifies them as red junglefowl, but they just look like normal chickens to me.
Taxonomists define species by the ability to reproduce1. So alligators and crocodiles are different species2 because they can’t reproduce with each other, while poodles and cocker spaniels are the same species, even if they look very different. Since chickens can still interbreed with the red junglefowl, they’re considered the same species.
Subspecies doesn’t have a rigorous definition. Basically, it is used to distinguish between populations of animals that could interbreed with each other, but usually don’t because of geography or some other difference between populations. Dogs can actually be considered a subspecies of wolf; it’s possible for them to mate, but they usually don’t because humans keep them apart (and a wolf would probably eat a chihuahua for a light snack). But other scientists insist they should be considered different species, because… common sense or something, I’m not familiar with the exact arguments. Anyway, the definition of subspecies is pretty hand wavy. According to a Reddit comment by a taxonomist, “Ultimately subspecies is a semantics argument, it’s a dispute of nomenclature and definitions. I'm personally against it because it has no real standing in evolution and phylogenies.”
So, getting back to the original question, should we consider a red junglefowl a chicken, since they’re the same species? Or does the word “chicken” only refer to the domesticated subspecies? The answer to whether the chicken or the egg came first depends on how you answer that question, because we’re trying to locate the exact moment chickens came into existence.
If you define chicken as the species gallus gallus… that still doesn’t help, because there is no single moment where you can say a new species is created, it’s a continual process of adaptations building up over time. But, if you arbitrarily decide to say “this bird is a chicken, its mother was not a chicken, this is the dividing line,” you still aren’t done yet. Because we still need to talk about eggs.
“Egg” is the name of the female reproductive cell of the mother bird, and we’ve already decided that the mother is not a chicken. So the last two questions you need to ask are: do you consider the egg a chicken egg before it is fertilized, or is it only a chicken egg after? And do you consider the chicken to exist as soon as the egg is fertilized, or sometime after it has started to develop? If you answer “immediately after fertilization” for both of those questions, then that means that the chicken and the egg came into existence at the exact same time, so neither came first. For most other combinations of answers, you’ll have to conclude that the egg came first.
Now, what if you restrict your definition of “chicken” to only include the subspecies gallus gallus domesticus? Then, since subspecies is already such a subjective category and we need to draw the line somewhere, I have no qualms with claiming that the subspecies was created when the first chicken was domesticated. In that case, the first chicken was created by reclassifying (what I assume was) an adult junglefowl as a chicken, which implies that the chicken came before the chicken egg did.
But my wife reminded me that females are born with their entire lifetime supply of egg cells already inside them, and I looked it up and this extends to chickens as well. So, if you decide you want to count those egg cells as chicken eggs, then we once again conclude that the first chicken and the first chicken egg came into existence at the same time.
We now have three different answers to our question. Depending on how you define different terms and where you draw arbitrary lines, you can say that either 1. The chicken came first, 2. The egg came first, or 3. Neither came first because they were both created in the exact same moment.
I have two takeaways from this discussion. The first is that some questions we ask are not questions about the world, they are questions about our language. The universe doesn’t care what kinds of things we label “chicken,” it just cares that there happen to be a bunch of atoms arranged into feathers and beaks and all the fleshy bits, and we often find it convenient to refer to this arrangement as a “chicken”. When we ask a question like “which came first, the chicken or the chicken egg?” it’s really a question about how we define different words. Too often, when people disagree, they end up talking past each other because they don’t realize that the disagreement is actually about how they are defining different words.
The second takeaway is that, once we defined our terms with sufficient detail, we were able to find an answer to the chicken and egg question. One of the most amazing things about the universe is that it is scrutable–we can find answers to the questions we ask. Having the confidence to ask a question, look for an answer, and then believe the answer when you find it is an underrated skill.
The question “which came first, the chicken or the egg?” is a famously unanswerable question, and yet, we found multiple different answers to it. It’s a little weird that a question like this could have an answer that’s so subjective. But I still think the best answer is that dinosaur eggs existed long before chickens ever did, and there’s nothing subjective about that.
Since Neanderthals can and did interbreed with humans, you’d have to consider them to be the same species as us if you want to hold to a strict definition. There’s actually a big academic debate going on about what to do in situations like this, where the two sides are called lumpers and splitters.
Alligators and crocodiles are actually entirely different families, and their lines diverged 80-90 million years ago. I just used them as an example because in my mind they’re basically the same thing, even if taxonomy disagrees.
I think I would generally refer to the egg as the female gamete and supportive structure independent of fertilization and embryogenesis. With that definition, we could say the first transgenic chicken came before the first transgenic chicken egg.