Burushaski is formally a language isolate spoken in the far northwest of Pakistan near the border with China in the Hunza Valley. It is still alive and may have 30,000 speakers.
Burushaski people are interesting in that they live a very long time. The Hunza has one of the largest populations of centenarians on Earth. No one knows why they live so long except that they live in mountainous terrain and walk up and down steep hills for most of their lives as another long-lived people, the Sardinians, also do. Their diet has also been studied, and it turns out that two staples are apricots and yogurt, for whatever that is worth. They live at a very high altitude also. Whether that factors into longevity is not known.
Method and Conclusion. See here.
Results. A ratings system was designed in terms of how difficult it would be for an English-language speaker to learn the language. In the case of English, English was judged according to how hard it would be for a non-English speaker to learn the language. Speaking, reading and writing were all considered.
Ratings: Languages are rated 1-6, easiest to hardest. 1 = easiest, 2 = moderately easy to average, 3 = average to moderately difficult, 4 = very difficult, 5 = extremely difficult, 6 = most difficult of all. Ratings are impressionistic.
Time needed. Time needed for an English language speaker to learn the language “reasonably well”: Level 1 languages = 3 months-1 year. Level 2 languages = 6 months-1 year. Level 3 languages = 1-2 years. Level 4 languages = 2 years. Level 5 languages = 3-4 years, but some may take longer. Level 6 languages = more than 4 years.
Burushaski is often thought to be a language isolate, related to no other languages, however, I think it is Dene-Caucasian. It is spoken in the Himalaya Mountains of far northern Pakistan in an area called the Hunza. It’s verb conjugation is complex, it has a lot of inflections, there are complicated ways of making sentences depending on many factors, and it is an ergative language, which is hard to learn for speakers of non-ergative languages. In addition, there are very few to no cognates for the vocabulary.
Burushaski is rated 6, hardest of all.