Finally proved: Which came first, hen or egg?

It’s an old riddle that’s sparked many arguments through the ages: was it the hen or the egg that came first? It’s such a tricky question because you need a hen to lay an egg, but hens 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 now!

The eggs we see today first came on the scene with the evolution of the first amniotes many millions of years ago. Prior to their arrival, most animals relied on water for reproduction, laying their eggs in ponds and other moist environments so that the eggs didn’t dry out.

At some point, a different kind of egg began to evolve, which had three extra membranes inside: the chorion, amnion and allantois. Each membrane has a slightly different function but the addition of all these extra layers provided a conveniently enclosed, all-in-one life support system. An embryo which takes in stored nutrients. The extra fluids encased in the amnion, plus the tough outer shell, provide extra protection too.

The very first chicken in existence would have been the result of a genetic mutation (or mutations) taking place in a zygote produced by two almost-chickens (or proto-chickens).

This means two proto-chickens mated, combining their DNA together to form the very first cell of the very first chicken. So who were the likely parents of this first One True Chicken? The red junglefowl (Gallus gallus) is native to a range of south-eastern Asian countries including India, southern China, Indonesia, Malaysia, Singapore and Indonesia.

Back to our original question: with amniotic eggs showing up roughly 340 million or so years ago, and the first chickens evolving at around 58 thousand years ago at the earliest, it’s a safe bet to say the egg came first.