Mothers who kill their offspring: testing evolutionary hypothesis in a 110-case Italian sample.

Objectives: This research aimed to identify incidents of mothers in Italy killing their own children and to test an adaptive evolutionary hypothesis to explain their occurrence.

Methods: 110 cases of mothers killing 123 of their own offspring from 1976 to 2010 were analyzed. Each case was classified using 13 dichotomic variables. Descriptive statistics and hierarchical cluster analysis were performed both for cases and variables, and significant differences between clusters were analyzed.

Results: The Italian sample of neonaticides (killings of children within the first day of life) was found to satisfy all evolutionary predictions for an evolved behavioral, emotional and motivational pattern to increase fitness, showing a consistent profile for offending mothers. Relatively young, poor women with no partner kill their offspring non-violently, either directly or through abandonment, and they attempt to conceal the body. These women have no psychopathologies and never attempt suicide after killing their children. All neonaticide cases fall in a single cluster that is distinct from all other offspring killings by mothers. Infanticide (killing of children within the first year of life) and filicide (killing of children after the first year of life) do not significantly differ according to any of the variables measured. The common profile of mothers who have committed infanticide or filicide includes psychopathology, suicide or attempted suicide after killing their children, violent killing of their victims, and no attempt to conceal the victims' bodies. These results suggest that maternal infanticide and filicide represent an improper functioning of adaptation, and their profile are much more variable than those of neonaticide offenders.

Conclusion: Our study confirms that only neonaticide is an adaptive reproductive disinvestment, possibly evolved in the remote past, to increase the biological fitness of the mother by eliminating an unwanted newborn and saving resources for future offspring born in better conditions. Neonaticide is shown to be clearly distinct from infanticide and filicide and therefore should be approached, prevented, and judged differently.