On reversion to wild type, the distinction between light and heavy breeds must surely be as significant for performance as is personality traits ('flighty' or whatever). Modern meaties are fit only for eating, and in evolutionary terms, that's a real dead end (pun intended
) Natural selection is never going to favour being someone's dinner - unless you're a parasite who needs it for part of your lifecycle of course - but I digress; we're talking chickens.
Heritage breeds were often designed to be dual purpose, so decent layers, and a decent table bird in the cockerels and the tired old hens. The extra size that makes them brick shape may be one of the first things selected out again when they are not confined and entirely dependent on a keeper for all their needs. Anyone got experience of this? For example, reduction in size and weight of offspring of e.g. Australorp, Dorking, Ixworth, Norfolk Grey, Orpington, Sussex.

Heritage breeds were often designed to be dual purpose, so decent layers, and a decent table bird in the cockerels and the tired old hens. The extra size that makes them brick shape may be one of the first things selected out again when they are not confined and entirely dependent on a keeper for all their needs. Anyone got experience of this? For example, reduction in size and weight of offspring of e.g. Australorp, Dorking, Ixworth, Norfolk Grey, Orpington, Sussex.