I’ll probably get somebody mad before I’m through, but breeds are not natural. They are all manmade. Nature did not select for those features, man did.
The production breeds were selected for production traits. The first few were not breeds as we know them, more of types that maybe laid well or made good meat birds or both. Some specialized flocks were developed, but people in general were not worried about many things we now recognize as part of a breed. If they wanted chickens that laid well, what difference does feather color/pattern, eye color, number of points on the comb, any of that matter? A light colored meat bird will give you a prettier carcass so color does matter with them, but if you are just after meat, what difference does size of eggs or leg feathers make? Different people had different criteria so they developed different types.
Eventually this wasn’t good enough. Some people decided they wanted to compete with each other, who could grow the best chicken. But the word “best” is pretty subjective. The person doing the judging might have their own criteria so they had to write a Standard of Perfection (SOP) to define a breed. That way they at least knew what standard to breed to. This link takes you through how the Ameraucana were originally develop from Easter Eggers here in the States. There will be some similarities with how all breeds were developed, sometimes by groups, sometimes by individuals.
http://www.ameraucana.org/history.html
Each country has its own SOP for each breed. For example your SOP for Araucana allows a tail, in the US ours doesn’t. Australia uses the UK standard. The French Marans have feathers on the legs, it’s not a requirement over here. Your Crème Legbar standards allow three different shades of egg color. One group trying to get the breed recognized over here are working to get only two of those shades recognized.
If you think about it, what production benefit is there to have so many different color/patterns recognized for Sussex, Leghorn, Wyandotte, Rocks, etc? There are even red and white Rhode Island Red’s. Someone explain that to me please. It’s purely for show.
The decorative breeds were originally kept because they were decorative or unusual. Normally it would have been royalty or rich people that could afford them. They were bred to make them pretty or unusual. But eventually some people wanted to compete and show them so they wrote SOP’s. When someone writes an SOP and gets it accepted is when breeds as we know them ae developed. Until then, they are just “types”.