Which came first, the chicken or the egg?

 This is for informational purposes only. For medical advice or diagnosis, consult a professional.

From a biological standpoint, the egg came first. Here's why:

 * Evolution: Chickens evolved from earlier bird-like species. These ancestors laid eggs, just as modern birds do.

 * Defining the "Chicken Egg": A true "chicken egg" can only be laid by a chicken. So, the first chicken egg was laid by a bird that wasn't quite a chicken yet.

Let me know if you'd like to explore this topic further!