The everyday sadists among us.
yes, thanks to the "Shades of Grey" trilogy, the NYTimes now declares this is normal behavior.
Related item: Nature's Fourth Trimester abortions.
yes, it's "natural" and was "common" in the past, goes the narrative, (implying that we should legalize infanticide).
What is not recognized is that usually such things happened when the families had no choice, because of severe poverty where another mouth would mean not enough food.
I am reading a book on the Eskimos in Canada, which noted that "infanticide" of girls and the deaths of the weak/crippled elderly stopped as soon as the gov't there started granting family allowances so that familes could survive.
Ditto for twins in Africa: not enough milk for two and so both would die...but with more money and canned milk/formula now an alternative, it is rarely done nowadays.
And it was rarely a free "choice": Pearl Buck tells of Chinese women weeping when they related killing their girl babies during a famine, and in Africa, one older lady mentioned that when she had twins, her husband's mother killed them, and she was so upset that she left that husband (and later married again.)
No, infanticide happened, but not when there were alternatives (hence stories of abandoned babies taken to monasteries, or those abandoned in ancient Rome being saved by those who would bring them up and sell them as slaves, or stories of Christians who saved these babies).
And babies saved include people like Darius and Oedepus...or Paris of Troy...