Spurs are pretty common in hens. In fact, I don't think I've ever seen a hen that didn't have a small round bump in the scale where the spur belongs. Some grow pretty long. A lot of gamefowl have them, it has long been a trait selected for, in the belief that it is a sign of the virility of her sons. A lot of chicken breeds have gamefowl in them somewhere. Either in their original makeup, (if Maly or Cornish is listed in the breeds makeup, they are descended from games), or added in later to fix color, (games come in a lot of color patterns). Going way back, there were probably more game chickens raised than anything else. Before people had TV and sports stadiums they had to have something to watch. You don't think that people that lived in a jungle full of food domesticated a bony 4 pound jungle bird that laid 20 eggs a year in a hidden nest for eggs and meat, do you?