Burushaski is a language spoken in northern Pakistan and Kashmir. It is spoken by 40,000 to 50,000 people today. Before the Aryans and Dravidians came, Burushaski was once a widely spoken. Burushaski is described as a complex language. They have verbal forms for males, females, animals/objects, and objects. They have a number system based on 20 and 40. Burushaski largely was an unwritten language. It has no known relatives and some believe it maybe a remnant of a prehistoric language. Burushaski is like Ainu and Basque, language isolate with no known relatives. Some linguists have attempted to link Burushaski with Basque, Nubian, Sumerian, Caucasian, Ainu, Paleo-Siberian, and Indo-European.
Language Museum-Burushaski
Burushaski: An Extraordinary Language in the Karakoram Mountains
Wikipedia-Burushaski
The Indo-European and Paleo-balkanic affinities of Burushaski
Basic Burushaski Etymologies