Answer:

It’s that old riddle that’s sparked many arguments through the ages: was it the chicken or the egg that came first? It’s such a tricky question because you need a chicken to lay an egg, but chickens come from eggs, leaving us with an intractable circle of clucky, feathery life that apparently has no clear starting point.

Thankfully, there’s no need to keep brooding over this forever. This is a riddle we can unscramble with the tools of science—more specifically, the principles of evolutionary biology.

Let’s get cracking.

The first eggs

Eggs are found throughout the animal kingdom. Technically speaking, an egg is simply the membrane-bound vessel inside which an embryo can grow and develop until it can survive on its own.