 The British tried again in 1939, as did the independent Tanzanian government in 1965 and 1990, and various foreign missionary groups since the 1960s.Although many attempts were forceful, they by and large failed; generally the Hadza willingly settle and take advantage of provided food, but leave and return to foraging when the food runs out; few have adopted farming.Another problem is disease – because their communities are sparse and isolated, few Hadza are immune to common infectious diseases such as measles, which thrive in sedentary communities, and several settlement attempts ended with outbreaks of illness resulting in many deaths, particularly of children.