Vanhanen developed an interest in evolutionary biology after studying E. O. Wilson's sociobiology and later in his career wrote about intelligence and inequality. He supported applying evolutionary and genetic methods to social sciences.[2] However, most of his academic work dealt with democratization, which he had studied with international comparative methods. Vanhanen was known for his Index of Democratization.[3]
In 2004, the Ombudsman of Minorities, Mikko Puumalainen, asked the police to start an investigation regarding Vanhanen's interview with a Helsingin Sanomat magazine Kuukausiliite, in which he stated that "Whereas the average IQ of Finns is 97, in Africa it is between 60 and 70. Differences in intelligence are the most significant factor in explaining poverty".[4] The Finnish National Bureau of Investigations was considering launching a preliminary investigation on Vanhanen's speech but later decided against it, not finding that he had incited hatred against an ethnic group or committed any other crime.[5]
Vanhanen, Tatu (1975). Political and social structures: American countries, 1850-1973. Tampere, Finland: Tampere University Press. ISBN9789514403019.
Vanhanen, Tatu (1976). Political and social structures: Part 2: European countries 1850-1974. Tampere, Finland: Tampere University Press. ISBN9780835702539.
Vanhanen, Tatu (1978). Multi-party democracy in action. Tampere, Finland: Tampere University Press. ISBN9789514406935.
Vanhanen, Tatu (1979). Power and the means of power: a study of 119 Asian, European, American, and African states, 1850-1975. University Microfilms International. ISBN9780835703987.
Vanhanen, Tatu; Lynn, Richard (2012). Intelligence: A unifying construct for the social sciences. Ulster: Ulster Institute for Social Research. ISBN9780956881175.
Vanhanen, Tatu (2014). Global inequality as a consequence of human diversity: A new theory tested by empirical evidence. Ulster: Ulster Institute for Social Research. ISBN9780957391376.