It was thought that this age old debate had been settled once and for all and even brain-box Stephen Hawking assured us all the the egg came first because reptiles were hatching out of eggs long before chicken eggs came on the scene. However, if the egg we're talking about is a chicken's egg, then scientists made a discovery back in 2010 that would mean the chicken actually came first. There is a protein called ovocledidin-17 that is only found in the ovaries of chickens and controls the production of the shell by converting the calcium carbonate into calcite crystals which make up the shell. It is only when this happens that the egg can truly be called a chicken's egg, but if the protein is only found in the ovaries of chickens, then the chicken must have come first. Following? It doesn't really matter if you aren't because the argument is largely semantic. If the question is whether the chicken or chicken's egg came first, then the answer is chicken. If the egg is just any old egg, then the answer is egg (say egg one more time).