The Gypsy population has been composite from the very beginning, with different ethnic groups brought together during their initial great migration from India. The population came into being outside of India, though the various ethnic elements began inside India. This is supported linguistically and increasingly more based on history. For the extensive amount of Persian and Byzantine Greek influence upon the Romany language, members of the migration out of India stayed in these areas long enough for this to occur, and they no doubt brought members of those populations into the evolving Romany population. The fragmentation of the Romany population occurred on a major scale after their arrival into Europe in the 14th century. Once in Europe, their particular ability to adjust to outside groups continued, and in some places, the Romany element was dominant enough to assimilate outsiders. (The first European descriptions of the Roma upon their entering Europe emphasised their dark skin and black hair. Through integration with Europeans over the centuries, Gypsies today can also be found with light skin and hair.) In other places, the Romany element was too small to maintain its discrete identity and it was lost, while contributing to the group into which they were absorbed. The Romany population has grown differently in different places, to the point that one group may deny the legitimacy of another group. However, all groups maintain to a greater or lesser degree the barrier between who is Roma and who is not. Thus, there are populations of Romany who have incorporated a substantial foreign genetic element from outside of India, but who remain in terms of their own self-perception Roma, and who speak Romany. Despite what some groups may believe, there is no group that can call themselves the one, "true" Roma. What may be accepted as ,true-Roma" by one group may be gadje to another. Romany culture is diverse, with many traditions and customs, and all tribes around the world have their own individual beliefs and tenets.