They begin with the premise that the female of most species has always been more sexually reserved than the male. If one interprets this sexual politics as a parent's propensity to invest in his/her legitimate child at the cost of his/her ability to sire and bring up a bastard, and if this imbalance of investment in the parents can be measured, psychologists believe curiosities such as male lust and female coyness, love and jealousy, fidelity and infidelity can be better understood.
