and fetal resorption are active areas of study. In general, females with more bearing opportunities may value offspring less, and may also arrange bearing opportunities to maximize the food and protection from mates. An important concept in sociobiology is that temperament traits exist in an ecological balance. Just as an expansion of a sheep population might encourage the expansion of a wolf population, an expansion of altruistic traits within a gene pool may also encourage increasing numbers of individuals with dependent traits. Studies of human behavior genetics have generally found behavioral traits such as creativity, extroversion, aggressiveness, and IQ have high heritability. The researchers who carry out those studies are careful to point out that heritability does not constrain the influence that environmental or cultural factors may have on those traits. Various theorists have argued that in some environments criminal behavior might be adaptive. The evolutionary neuroandrogenic (ENA) theory, by sociologist/criminologist Lee Ellis, posits that female sexual selection has led to increased competitive behavior among men, sometimes resulting in criminality. In another theory, Mark van Vugt argues that a history of intergroup conflict for resources between men have led to differences in violence and aggression between men and women. The novelist Elias Canetti also has noted applications of sociobiological theory to cultural practices such as slavery and autocracy. Support for premise Genetic mouse mutants illustrate the power that genes exert on behaviour. For example, the transcription factor FEV (aka Pet1), through its role in maintaining the serotonergic system in the brain, is required for normal aggressive and anxiety-like behavior. Thus, when FEV is genetically deleted from the mouse genome, male mice will instantly attack other males, whereas their wild-type counterparts take significantly longer to initiate violent behaviour. In addition, FEV has been shown to be required for correct maternal behaviour in mice, such that offspring of mothers without the FEV factor do not survive unless cross-fostered to other wild-type female mice. A genetic basis for instinctive behavioural traits among non-human species, such as in the above example, is commonly accepted among many biologists; however, attempting to use a genetic basis to explain complex behaviours in human societies has remained extremely controversial. Reception Steven Pinker argues that critics have been overly swayed by politics and a fear of biological determinism, accusing among others Stephen Jay Gould and Richard Lewontin of being "radical scientists", whose stance on human nature is influenced by