The question of which came first, the chicken or the egg, is one of those questions that reveals the religious bias many of us still carry with us into these issues. Only one with an ex-nihilo view of creation could consider the question a challenge. From an evolutionary perspective the answer is obvious: going backwards through the chicken lineage will eventually come to egg-laying creatures which aren't chickens. Martin Rundkvist explains:
"Biologically, a member of the chicken species could be defined by a list of alleles that must be present in its DNA if we're to call it a chicken. And somewhere, sometime, the first bird that fulfilled that definition hatched. It hatched out of an egg laid by a non-chicken. As an adult, the first chicken (being lonely) probably mated with a bird that did not quite fulfil our definition of chickenhood, and so the first chicken probably laid non-chicken eggs. Out of these eggs hatched birds that almost, but not quite, fulfilled our definition of chickenhood. In subsequent generations, chicken eggs became more and more common. Later, after the geologically instantaneous speciation period, birds fulfilling the chicken species-definition became common and so chicken eggs were reliably produced generation after generation."