Mystery - SOLVED.

British scientists believe they have found the answer to an ages-old question: Which came first, the chicken or the egg?

Scientists cracked the puzzle after discovering that the formation of eggs is possible only thanks to a protein found in chicken's ovaries. That means eggs have to be formed in chickens first.

The protein -- called ovocledidin-17 (OC-17) -- speeds up the development of the shell. Researchers from Sheffield and Warwick universities in England laid out their findings in the paper "Structural Control of Crystal Nuclei by an Eggshell Protein."

They used a supercomputer to zoom in on the formation of an egg and realized the protein is vital in kick-starting the crystallization process. It works by converting calcium carbonate into the calcite crystals that make up the egg shell.

Dr Colin Freeman, from Sheffield University's Department of Engineering Materials, said "it had long been suspected that the egg came first -- but now we have the scientific proof that shows that in fact the chicken came first."

"The protein had been identified before and it was linked to egg formation, but by examining it closely we have been able to see how it controls the process," Freeman said.

"It's very interesting to find that different types of avian species seem to have a variation of the protein that does the same job."