A question from formspring.me:

“Who came first, the egg or the chicken?!”

The egg, of course! Reptiles were laying eggs before the first bird was even around. Now, if you’re specifically talking about a chicken egg, it gets a little more complicated. I was going to create my own explanation, but I think Wikipedia already does quite a nice job:

Since DNA can be modified only before birth, a mutation must have taken place at conception or within an egg such that an animal similar to a chicken, but not a chicken, laid the first chicken egg.[8][9] In this light, both the egg and the chicken evolved simultaneously from birds that were not chickens and did not lay chicken eggs but gradually became more and more like chickens over time.

However, a mutation in one individual is not normally considered a new species. A speciation event involves the separation of one population from its parent population, so that interbreeding ceases; this is the process whereby domesticated animals are genetically separated from their wild forebears. The whole separated group can then be recognized as a new species.

The modern chicken was believed to have descended from another closely related species of birds, the red junglefowl, but recently discovered genetic evidence suggests that the modern domestic chicken is a hybrid descendant of both the red junglefowl and the grey junglefowl.[10] Assuming the evidence bears out, a hybrid is a compelling scenario that the chicken egg, based on the second definition, came before the chicken.

There you go – a scientific answer to an age-old question! Of course, the Biblical viewpoint is that the chicken came first, since God created birds on the fourth day and made no mention of eggs. Guess proving the Bible wrong again is the cherry on top.