Touche'. I actually thought I was on to something there ... ... I think I still am, 'chicken' and 'egg' are human constructs. A chicken became a 'chicken', and an egg became an 'egg', when man first declared them as such. Therefore, they most likely arrived simultaneously.
Which came first-the chicken or the OWNED? Im sure they just "materialised out of potentiality", like those magistrates Z10 mentioned somewhere.
By accident ? ISH ... All it would require in the beginning would be no chicken and no egg. Then as the ickle wikkle microbes went off dividing & turning into different ones by small mutation over billions of years, some formed a layer which was protective so they could grow outside the parent and they survived better. They went on reproducing that way. The microbe, then the start of the egg. Then the start of a chicken and the egg, constantly mutating. Along with a few million years and lots of changes inbetween. Strictly speaking the 'chicken' microbe was first. Then the 'chicken' stock cube. Then the egg and farmers don't want chickens with any more than 2 legs becuase they can't catch them.