Finally Answered! Which Came First, the Chicken or the Egg? (2024)

The granddaddy of causality dilemmas has a solution, and we have the simple science to explain it.

Former Senior Editorial Director

Hunter College
F.I.T., State University of New York
Cornell University

Melissa Breyer is Treehugger’s former senior editorial director. Her writing and photography have been featured in The New York Times, The Guardian, National Geographic, Audubon Magazine, and elsewhere.

Learn about our editorial process

Updated August 16, 2023

Finally Answered! Which Came First, the Chicken or the Egg? (2)

Science

Which came first, the chicken or the egg? The chicken, no, the egg, no, the chicken, no, the egg. It's enough to make your head spin right off your neck.

Spoiler: The egg came first! But how?

We've all been through the logic; most of us end up at the same place. As Luna Lovegood, the quirky witch from Harry Potter, put it when asked the riddle, "A circle has no beginning." And indeed, attempting to identify the answer to this classic causality dilemma is an exercise in utter futility. For those who don't have a pat story involving a divine being who turns out perfectly formed species, it's a no-win situation.

Causality Dilemma

A causality dilemma is more commonly known as the chicken or the egg paradox! It characterizes situations in which it is challenging to determine between the cause of an event and the effect.

Even the Greek-Roman philosopher Plutarch couldn't exactly come up with a solution. He went with the decidedly non-answer answer that the egg was first as “it begets and contains everything” ... and also that the chicken was first because, in the beginning, creation was “vigorous and perfect" and "self-sufficient and entire.”

But that doesn't stop us from asking. Luckily for people kept awake at night by such quandaries, NPR's Robert Krulwich got to the bottom of the dilemma when he, thankfully, stumbled across the video below.

Basically, many, many moons ago, there was a chicken-like bird. It was genetically close to a chicken but wasn't a full-blown chicken yet. The video calls it a proto-chicken. So proto-hen laid an egg, and proto-rooster fertilized it. But when the genes from mom and dad almost-chicken fused, they combined in a new way, creating a mutation that accidentally made the baby different from its parents.

Finally Answered! Which Came First, the Chicken or the Egg? (3)

Although it would take millennia for the difference to be noticed, that egg was different enough to become the official progenitor of a new species, now known as ... the chicken!

So, in a nutshell (or an eggshell, if you will), two birds that weren't really chickens created a chicken egg, and hence, we have an answer: The egg came first, and then it hatched a chicken.

Finally Answered! Which Came First, the Chicken or the Egg? (4)

Maybe the question we should really be asking is: Which came first, the proto-chicken or the proto-chicken egg?