Daly Martin, Perry Gretchen
Department of Psychology, Neuroscience & Behavior, McMaster University, Hamilton, ON, Canada.
Department of Sociology, Anthropology & Human Services, University of Canterbury, Christchurch, New Zealand.
Front Psychol. 2022 Jun 13;13:924238. doi: 10.3389/fpsyg.2022.924238. eCollection 2022.
Darwin's theory of sexual selection provides a useful framework for understanding the behavior of stepparents. A non-human animal whose new mate has dependent young may kill, ignore, or adopt the predecessor's progeny. The third option has been interpreted as courtship ("mating effort"), and whether selection favors such investment over killing or ignoring the young apparently depends on aspects of the species-typical ecology and demography. The tripartite categorization of responses is a simplification, however, There is variability both within and between species along a continuum from rejection to "full adoption." The average stepparent invests less than the average birth parent, but more than nothing. Human stepparents have often been found to kill young children at higher rates than birth parents, but stepparental infanticide cannot plausibly be interpreted as a human adaptation, both because it is extremely rare and because it is almost certainly more likely to reduce the killer's fitness than to raise it. How sexual selection theory remains relevant to human stepparenting is by suggesting testable hypotheses about predictors of the variability in stepparental investment.
达尔文的性选择理论为理解继父母的行为提供了一个有用的框架。一种新配偶有幼子的非人类动物可能会杀死、忽视或收养前任的后代。第三种选择被解释为求爱行为（“交配努力”），而选择是否青睐这种对幼子的投入而非杀死或忽视他们，显然取决于物种典型的生态和人口统计学特征。然而，这种三方反应分类是一种简化。在物种内部和物种之间，从拒绝到“完全收养”存在一个连续体的变异性。继父母的平均投入比亲生父母少，但也并非毫无投入。人们经常发现，人类继父母杀害幼儿的比率高于亲生父母，但继父母杀婴行为很难被合理地解释为一种人类适应性行为，这既是因为这种行为极为罕见，也是因为几乎可以肯定，这更有可能降低杀人者的适应性而非提高其适应性。性选择理论与人类继父母行为的相关性在于，它提出了关于继父母投入变异性预测因素的可检验假设。
