Basically they argue that single motherhood weakened mostly the male children, because the sisters in such one parent families perform better in life than the brothers. In normal families, there is no difference or the male child perform better.

In other words, the lack of father harms more the male child than the female child. Thus if you want to weaken men, push for single motherhood. Apparently, having a father is more important for boys than for girls.

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In a 2016 paper, David Autor, an economist at M.I.T., and four co-authors, measured academic and economic outcomes of brothers and sisters in Florida born in the decade between 1992 and 2002. For boys and girls raised in two-parent households, there were only modest differences between the sexes in terms of success at school, and boys tended to earn more than their sisters in early adulthood. Among children raised in single-parent households, however, boys performed significantly less well than their sisters in school, and their employment rate as young adults was lower. “Relative to their sisters,” Autor and his collaborators wrote, “boys born to disadvantaged families” — with disadvantage measured here by mother’s marital status and education — “have higher rates of disciplinary problems, lower achievement scores, and fewer high-school completions.”

When the children in the study reached early adulthood, the same pattern emerged in employment: Employment rates of young women are nearly invariant to family marital status, while the employment rates of young adult men from non-married families are eight to ten percentage points below those from married families at all income levels. Autor and his co-authors conclude that family structure “is more consequential for the skills development and labor market outcomes of boys than girls.”

From another perspective altogether, Allan Schore, a professor of psychiatry and biobehavioral sciences at the U.C.L.A. School of Medicine, explores the slower development among boys “in right-brain attachment functions.” This “maturational delay” in brain function, Schore writes in an essay that was published earlier this year in the Infant Mental Health Journal, “All Our Sons: The Developmental Neurobiology and Neuroendocrinology of Boys at Risk,” makes boys more vulnerable over a longer period of time to stressors in the social environment and toxins in the physical environment that negatively impact right-brain development. This vulnerability, in turn, makes boys more susceptible to attention deficit hyperactivity disorder, and conduct disorders as well as the epigenetic mechanisms that can account for the recent widespread increase of these disorders in U.S. culture. Schore argues that a major factor in rising dysfunction among boys and men in this country is the failure of the United States to provide longer periods of paid parental leave, with the result that many infants are placed in day care when they are six weeks old.

Starting day care at six weeks, Schore writes, is “the exact time of the initiation of the postnatal testosterone surge found only in males.” Schore notes that “research has documented that boys more so than girls raised in single-mother families show twice the rate of behavioral problems than do boys in two-parent families” and argues that a “mis-attuned insecure mother” can be “a source of considerable relational stress, especially when the immature male toddler is expressing high levels of dysregulated aggression or fear.” When a child is 18 to 24 months old, fathers play a crucial role, Schore writes, pointing to the male infant’s attachment transactions with the father in the second year, when he is critically involved in not only androgen-controlled rough-and-tumble play but in facilitating the male (and female) toddler’s aggression regulation. This same period (18–24 months) involves the initiation of a critical period of growth in the left hemisphere, and so the “paternal attachment system” of father-son interactions would presumably forge an androgenic imprint in the toddler’s evolving left-brain circuits, including the left dorsolateral prefrontal cortex, allowing for his regulation of the male toddler’s testosterone-induced aggression (“terrible twos”).

Source: https://www.nytimes.com/2017/03/16/opinion/the-increasing-significance-of-the-decline-of-men.html?_r=0