Philosophers have always presented this dilemma as the classic unanswerable conundrum - a chicken can't exit without and egg, and vice versa - but it does have a scientific explanation. It just depends on whether the egg in question is a chicken's egg or any type of egg at all.

If the egg is any type of egg, the answer is straightforward. Over millions of years, some reptiles evolved into a birdlike dinosaur called the achaeopteryx. From this animal, birdlife then evolved. The first actual bird resembling a chicken was the mutant offspring of two reptile/bird hybrids that were almost chickens, who laid an egg from which emerged the first chicken-type creature. In this case, the egg came first.

If it is assumed that the egg must be a chicken's egg, the question becomes more complex and its answer depends on what is considered a chicken's egg. Firstly, if a hybrid chicken laid an actual chicken's egg, containing the first chicken, then the egg came first.

However, if a chicken's egg is an egg that must be laid by a chicken, then a full chicken must have laid the first chicken's egg, which means that the chicken must have come first.

Combining these two ideas, a third view is that a chicken must be hatched from a chicken's egg, and that a chicken's egg must have existed first in order to lay the first chicken's egg, out of which hatched a chicken. This hatched chicken would be the first chicken, despite its mother being the first true chicken.

So, while the answer depends on how the egg is defined, an answer can be reached for every occasion.