Which came first - the egg or the chicken? How?

Here is the key to the mystery to this egg VS chicken issue:

The ultimate victor is the chicken, not the egg.

According to the report from the researchers of  University of Sheffield and Warwick, a protein called ovocledidin-17 was found to be responsible for producing eggshells, and found only in the chicken's ovaries.

Here's how it works. The OC-17 attaches itself to the calcium carbonate particles to set up a formation, which looks like a crystal structure. It is dropped off once its crystal nucleus is big enough to grow on its own and so this protein replicates more of the similar types of eggshells, causing the amazing egg to be formed.

So, now you know the truth, the chicken came first before the egg.