Sumatra has a wealth of natural resources and wildlife, massive rivers like muddy facsimiles of the Amazon, and some interesting architecture. It is almost four times the size of neighbouring Java, but supports less than a quarter of the population. During Dutch rule, it provided the world with large quantities of oil, rubber, pepper and coffee, and these seemingly inexhaustible resources continue to prop up the Indonesian economy today. Sumatra is home to a number of different races and peoples: the former head-hunters and cannibals of the Batak regions; the matrilineal Muslim Minangkabau and the primitive groups of the Mentawai Islands.