The importance of fathers in their children’s lives has been underscored by Canadian research. Hands-on parenting by the dad tends to make kids smarter and better behaved, the study published in the Canadian Journal of Behavioural Science found.
Lead researcher Erin Pougnet says:

"Compared with other children with absentee dads, kids whose fathers were active parents in early and middle childhood had fewer behaviour problems and higher intellectual abilities as they grew older -- even among socio-economically at-risk families."
Just make a note of that, will you, in case anyone says it’s all about poverty.
Two things in particular to note. First, girls are most affected by the absence of their father:

"Girls whose fathers were absent during their middle childhood had significantly higher levels of emotional problems at school than girls whose fathers were present," says Pougnet.
Also it seems to make no difference whether the father actually lives under the same roof:

"Regardless of whether fathers lived with their children, their ability to set appropriate limits and structure their children's behaviour positively influenced problem-solving and decreased emotional problems, such as sadness, social withdrawal and anxiety," continues Pougnet.
Um, OK. A dad who is at least “around” and actively involved is going to have more effect than one who is completely absent. But the researchers seem anxious to downplay the effect of active fathering:

"While our study examined the important role dads play in the development of their children, kids don't necessarily do poorly without their fathers," stresses co-author Lisa A. Serbin, a professor in the Concordia Department of Psychology and a CRDH member. "Mothers and other caregivers are also important. No doubt fathers have a major impact, but there are definitely many alternative ways to raise a healthy child. Some kids with no contact with fathers, or with distant dads, do well intellectually and emotionally."
“Many” alternative ways? This is an opinion, not a finding, I think, and one perhaps shaped by the fact that in Quebec province where the study was done, 22 per cent of households with children have no biological father present. That’s nearly twice the rate of Canada as a whole, 13 per cent. Promoting intact married families could certainly look as though it is in the too hard basket.
I have the full journal article to read and will come back to this study soon. Hat tip to Joe Atkinson