of mtDNA among Afghan Pashtuns belongs to West Eurasian lineages, and share a greater affinity with West Eurasian and Central Asian populations rather than to populations of South Asia or East Asia. The haplogroup analysis indicates the Pashtuns and Tajiks share some sort of ancestral heritage. The study also states that among the studied ethnic groups, the Pashtuns have the greatest HVS-I sequence diversity. A 2019 study on autosomal STR profiles of the populations of South and North Afghanistan states: Definitions The most prominent views amongst Pashtuns as to who exactly qualifies as a Pashtun are: Those who use Pashto as their first language. The Pashto language is "one of the primary markers of ethnic identity" amongst Pashtuns. Adherence to the code of Pashtunwali. The cultural definition requires Pashtuns to adhere to Pashtunwali codes. Belonging to a Pashtun tribe through patrilineal descent, based on an important orthodox law of Pashtunwali which mainly requires that only those who have a Pashtun father are Pashtun. This definition places less emphasis on the language. Tribes A prominent institution of the Pashtun people is the intricate system of tribes. The tribal system has several levels of organisation: the tribe they are in is from four 'greater' tribal groups: the Sarbani, the Bettani, the Gharghashti, and the Karlani. The tribe is then divided into kinship groups called khels, which in turn is divided into smaller groups (pllarina or plarganey), each consisting of several extended families called kahols. Durrani and Ghilji Pashtuns The Durranis and Ghiljis (or Ghilzais) are the two largest groups of Pashtuns, with approximately two-thirds of Afghan Pashtuns belonging to these confederations. The Durrani tribe has been more urban and politically successful, while the Ghiljis are more numerous, more rural, and reputedly tougher. In the 18th century, the groups collaborated at times and at other times fought each other. With a few gaps, Durranis ruled modern Afghanistan continuously until the Saur Revolution of 1978; the new communist rulers were Ghilji. Tribal allegiances are stronger among the Ghilji, while governance of the Durrani confederation is more to do with cross-tribal structures of land ownership. Language Pashto is the mother tongue of most Pashtuns. It is one of the two national languages of Afghanistan. In Pakistan, although being the second-largest language being spoken, it is often neglected officially in the education system. This has been criticised as adversely impacting the economic advancement of Pashtuns, as