Hello there,
This question remains in confusion all the time. And it is clear from the observations that all the chickens hatch from eggs and all chicken eggs are laid by chickens.
NPR's Robert Krulwich recently got to the bottom of the dilemma. His theory is given below.
Basically, many, many moons ago there was a chicken-like bird. It was genetically close to a chicken but wasn't a full-blown chicken yet. The video calls it a proto-chicken. So proto-hen laid an egg, and proto-rooster fertilized it. But when the genes from ma and pa almost-chicken fused, they combined in a new way, creating a mutation that accidentally made the baby different from its parents. Although it would take millennia for the difference to be noticed, that egg was different enough to become the official progenitor of a new species, now known as... the chicken! So in a nutshell (or an eggshell, if you like), two birds that weren't really chickens created a chicken egg, and hence, we have an answer: The egg came first, and then it hatched a chicken.
Hope this helps.
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile