Huh, that makes sense, I wonder if that's where the Cornish Cross came from, Pure Cornish to me look pretty gamey so maybe they are the ones that brought a lot of the breast meat into the cross.
A suggestion, and it would require maybe more pens than you would like so may not be something you are interested in. If you have hens from breeds that lay different color eggs, you could put 1 hen of each egg color in a pen together with a rooster, then you would know exactly who laid which egg...
You also have the weirdness of with most animals you know who the mother is and may not be sure on the father.. with chickens you usually only have 1 rooster in the pen so only 1 possible father but you haven't a clue on the mother... Added to the fun is the fact that in mammals the male is the...