There is no doubt that adopted children are as or more loved by their adoptive parents as children with respect to their biological parents. However, according to the studies of evolutionary psychologists Martin Daly Y Margo Wilson, there is a greater probability of infanticide among non-biological parents than among biological ones.
The probability of infanticide, in these cases, is a hundred times greater (It seems a lot, but given that infanticide in general by the male is an unlikely event, we are talking about many cases in percentage terms but few cases in their entirety).
One of the world's leading experts in evolutionary biology, Mark pagel, dissects the results of this study in his book Connected by culture in this way:
This statistical reason occurs even when other factors that could differ in these two family classes are taken into account. We must emphasize that the vast majority of adoptive parents are not given to abuse, much less infanticides. There are simply more both traits among these than among those.
This effect is called Cinderella Effect, and its validity comes from a wide variety of sources, including official reports of child abuse, clinical data, victim reports, and official homicide data. Evolutionary psychologists have also suggested that one of the causes of stepchild abuse can be the lack of attachment bond that the mother would normally form with her own child. As a result, it is highly recommended that the adoptive mother be present very early in life children, preferably immediately after birth, in order to avoid attachment disorders.
The costs of a man when raising a child who does not share his genes are evolutionarily enormous. Thanks to nepotism, a feeling of genetic proximity arises with children who are not biological. However, in a percentage of men, there may be a feeling that their children are not entirely theirs. In fact, given that it is estimated that between 5 and 10% of the children are not biological without the father knowing, evolutionarily human offspring could have favored anonymity in their early years:
Over time, as the risk for the newborn becomes less, it begins to resemble one or the other of its parents, or both. The hair and light eyes so common in Caucasian babies disappear in the majority around the second birthday. As one would expect from a strategy aimed at hiding our own identity, the genes that determine the final color of our eyes “turn off” at birth (unless they are going to be clear) to manifest as they mature the small.
The Cinderella effect, however, also has a critical sector. As the case of the philosopher of science David Buller, as part of his general criticism of evolutionary psychology. He argues, for example, that the Daly and Wilson conclusions are intrinsically biased, since they use the data from official documents, and officials who collect that the data are not trained to take special note of stepparents in front of biological parents. Burgess Y Drais They propose that child abuse is too complex to be fully explained by the genetic relationship alone, and cite other reasons for child abuse, such as social factors, ecological factors and the child's features, such as disability and age.
Martin Daly He argues against his critics in this way in this interview:
The evidence of the different treatment that discriminates against stepchildren is now national and overwhelming. Why this empirical fact (not "concept") has been so "unpopular" that many have wanted to disapprove it is a fascinating question and I cannot answer satisfactorily. Many people seem to think that it supports the “conservative” vision that considers divorce and remarriage as something bad and / or that “stigmatizes” stepparents and makes their task more difficult. But the facts are the facts and how they are going to be transformed into political arguments is something that has a double edge. Those who are motivated to distrust any discrimination against stepchildren seem not to notice the other side of the coin: their implicit assertion that there is no such thing as a specialized and individualized parental love!