Archaeological evidence suggests that the bird commonly known as the chicken (Gallus domesticus) is a domesticated version of the Indian and Southeast Asian Red Jungle Fowl (Gallus gallus) which is still found in the wild today. It is thought that the bird was first tamed in China around 6000 BC, with the birds moving into India by 2000 B.C. The chicken then spread from China to Russia and from there into Europe between 750 B.C. 42 A.D. Some scholars believe that the bird may have been domesticated first for its use in cockfighting, and only later used as a food source. The White Leghorn breed or crosses of this breed is the large white bird most commonly used in agriculture and for research, but there are over 400 different breeds of chickens. Chickens have a rigid social structure called the pecking order by which every bird establishes who is dominant and who is submissive in relationship to every other bird.