 Discussions of the viability of heritability measures were most heated in the 1970s and 1980s. In the 1970s discussions about IQ and race came to a head (this issue was revisited in the 1990s with the publication of Herrnstein and Murray (1994)), and in the late 1970s and early 1980s sociobiology came under critical scrutiny. Both proponents of the hereditary nature of IQ and sociobiologists made a connection between human behavioral traits and genes. Hereditarians in the IQ debates explicitly relied upon twin heritability analyses such as those introduced above. Critics of sociobiology and hereditarianism over IQ included biologists, philosophers and many social scientists as well as many left-leaning political and social activists (See Gould (1981), Paul (1998) and Segerstråle (2000) for some of the relevant history here).