It's like this, the chicken evolved from something else, but that creature was obviously laying eggs, so the first mutation that we would now call a chicken came from an egg lain by a non-chicken.. Thus therefore, the egg came first.
The problem with this idea is, the mutation was so small that it is impossible to determine the difference between the critter that laid the egg, and the chicken that hatched out. So, the chicken came first.
The wood carver chips little chunks of wood off the log, gradually forming it into the chair. At which chip does the log become the chair? Obviously it isn't the first, because the first is only a chip off the log. And it isn't the last, because before the last is only an incomplete chair. Same with the egg. It would take a tremendous number of mutations in the innards of another animal's egg to convert these innards into a chicken.
