What came first: the egg or the chicken?

The question, which really has a lot to unpack, is easily answered with the help of a biologist — and that’s why I’m writing to you today. Let’s start with the old logic: the egg comes from a chicken, which was born from an egg, which was laid by another chicken, which… You get the idea. We could go on like this for many lifetimes, many eggs and many chickens, and we still wouldn’t reach the final answer.

To find it, I suggest we take a trip back in time. (Don’t worry, you don’t need to leave where you are.)

Around 360 million years ago, four-limbed animals — known as tetrapods — lived peacefully, without the rush of our modern tetrapod lives. They reproduced and laid their eggs in water so they wouldn’t dry out. (Yes, they had left aquatic life behind, but not completely!)

“But chickens don’t lay eggs in water, Carla!” True — those eggs are different from chicken eggs. We’ll get there. Time went on, tetrapods continued their evolutionary process, and at least 312 million years ago some tetrapods appeared that produced eggs with special internal membranes — we call them amniotes. One of these membranes is called the amnion, and it protects the embryo inside the egg from shocks and dehydration.

This step was fundamental to evolution — without it, we wouldn’t be here! It made eggs more resistant and allowed animals to completely leave the aquatic environment behind and explore land — I still wonder whether that was the wisest decision. Millions of years continued to pass, animals kept evolving, adapting to different environments and diversifying in many ways. Mammals, reptiles and birds are very different from one another, but they share something in common: they all descend from the first amniotes. Yes, that’s right… We are distant cousins of ducks, alligators and dolphins.

So when did the chicken appear? Chickens are thought to have emerged around 58,000 years ago, when two proto-chickens (birds very similar to chickens, but not quite chickens) reproduced with each other. Add a few genetic mutations, and you have the evolutionary recipe for the first chicken.

So all doubts are settled: between the egg and the chicken, the egg came first!