Poultry are a good example of the longer a breed's been around and confined to a small area of the country then the more "fixed" it becomes. Our Dorkings, for instance, are like peas in a pod, even though we regularly bring in a new cockerel, but the Laced Wyandottes show considerable differences in things like lacing pattern and comb shape, even though we've bred only from correct birds for five generations. Our main sheep breed, the Southdown, was one of the first breeds to be selectively bred to improve wool and carcase, from around 1780, but some breeders are now bringing in French and NZ bloodlines of lineage which cannot be verified beyond a couple of generations and this has prompted the Society to initiate a survey with a view to perhaps splitting "Traditional" from "Improved" in much the same way as has happened to Aberdeen Angus and Hereford cattle.