Option 1: Quick read
https://www.si.edu/newsdesk/releases/ch ... -engineers
Option 2: Long read referenced in the above
https://www.pnas.org/content/111/17/6184
"The data presented here reveal that although the yellow skin allele was present on ∼10% of chromosomes in ancient European chickens, not a single ancient bird was homozygous for the Gray Junglefowl allele (and therefore capable of expressing the yellow skin phenotype) (Tables S1 and S2). This finding is consistent with 17th–19th century records suggesting that a number of widespread, prolific, and economically important breeds raised in western and southern Europe, including the Dorking, Houdan, Sultan, Spanish, or B/W Bantams, clearly had white legs, but the Hamburgh, Polish, Turkish, and Crève Cœur breeds had leg colors ranging between slate blue and dark leaden-blue (27, 37). However, some 17th century European breeds, including the Padua, did possess yellow legs (37) and the trait was explicitly mentioned in relation to heavy, fast-growing types, including Cochin, Brahma, and Malay breeds imported by sea (and therefore named Captain’s birds) from the Far East into Europe and the United States during the 1820s–1850s (27). It is therefore possible that the rise in frequency of the yellow skin phenotype occurred only after recent introductions of foreign birds to Europe and the breed formation process that consequently led to the creation of modern, widespread, commercial broiler, and egg-laying breeds. Tegetmeier (27), for example, noted the remarkable rapid growth and great size attained by crossbred birds produced by mating Cochins with the large traditional French Crève Cœur, La Flèche, and Houdan breeds. The ubiquity of the yellow skin phenotype in commercial, modern, and some rare, geographically restricted breeds can, therefore, be explained by rapid worldwide spread of newly synthesized commercial chickens. This suggestion is further supported by the fact that the yellow skin phenotype appears infrequently or is completely absent in rare breeds, such as the Friesian Fowl, Houdan, and Westfälischer Totleger (25)."
