The answer to the age-old question of which came first, the chicken or the egg, is that the egg came first. Eggs, which are just female sex cells, evolved more than a billion years ago, whereas chickens have only been around for about 50 million years. However, if were talking about the first chicken egg, the story changes. Chickens likely evolved from a subspecies of red jungle fowl around 50 million years ago, and at some point during the domestication process, the last ancestor of modern chickens would have laid an egg containing an embryo with enough genetic differences to make it distinct from its parent species. This embryonic chicken would have developed in the not-quite-chicken egg before hatching. Then, after reaching adulthood, it would go on to lay the first proper chicken egg. So, in a way, the chicken came first, but only in the sense that the first chicken egg was laid by a bird that was not quite a chicken yet.