Which came first, Chicken? Or Egg? The answer is that this is the wrong question. The trouble here is the word 'First's. A human life contains many firsts, so the word comes easily to our lips. For example, a creationist could ask how the metamorphosis of a butterfly occurred for the 'First time'. French is called a Romance language because it is descended from Roman, or to be more specific, Classical Latin. Across the last 2, 000 years, the language changed piece by piece, a word or emphasis at a time.
Documents from many of the centuries between, are written in a language somewhere between the two, not quite Latin, yet not quite French. So who was the first person to speak French? I think its plain to see that this was a very gradual evolution of the language. There was not first French speaker. Was there a first chicken? Some say there was. But Darwin suggests that species evolve slowly, over time. So imagine a lizard, which laid a lizard egg.
Millions of years later, its descendant was a chicken, which lays a chicken egg. But there was no moment when chicken-ness suddenly leapt into existence. Similarly, there was no first land animal, no first lung, and no first skeleton. Current scientific beliefs say that all of these came bit by bit. In short, if a species was created abruptly, then a chicken-and-egg question makes sense.
But if that species evolved, then there was no first chicken, and there was no first egg, the only true first was the original single celled organism that was created by a spontaneous chemical reaction in the primordial soup that was early Earth, from which all life as we know it evolved.