British scientists believe they have cracked the answer to the age-old question of which came first, the chicken or the egg?

Researchers have found that a protein called ovocleidin (OC-17) is crucial in the formulation of eggshells, and it is produced in the pregnant hen's ovaries, the Daily Express reports.

Therefore, the answer to the conundrum must be that the chicken came first.

Using a high-tech computer to look at the molecular structure of a shell, the team of scientists from the Universities of Sheffield and Warwick found that OC-17 acts as a catalyst, kick-starting the conversion of calcium carbonate in the chicken's body into calcite crystals.

They make up the hard shell that houses the yolk and its protective fluids while the chick develops.

"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," said Dr Colin Freeman, from Sheffield University.

"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."

But the researchers have not yet got an answer to how the protein-producing chicken existed in the first place.