High fertility is not the same as reproductive success among humans.
Raising a juvenile of our species properly takes a lot of time, energy, and resources. For the best results, parents should be involved and bonding with a new child for a good portion of every day to encourage a baby whose brain will hopefully thrive as a result of loving attention, gentle touch, early lessons, and positive reinforcement.
A kid's capacity to form long-term attachments across a lifetime is very dependant on how much time the parent(s) invested in spending with the child especially when he or she is young (but to some degree throughout their childhood):
http://www.ucdmc.ucdavis.edu/medicalcenter/healthtips/20100114_infant-bonding.html
There is no shortcut in this thing. You're either actively parenting a child or you are not...and if you are not, this child begins life at a disadvantage that gets worse with each missed developmental milestone.
Child maltreatment - and for infants and toddlers, the different between neglect and abuse is merely a matter of degree - can, and often will, do permanent damage:
https://www.cdc.gov/violenceprevention/childmaltreatment/consequences.html
http://www.nber.org/digest/jan07/w12171.html
To be blunt, every walking testicle I've had the misfortune of trying to help - and by "walking testicle," I mean a deadbeat and habitual "father" of multiple children by multiple women - has had an overweening sense of entitlement: They believe they're entitled, among other things, to control their interviews via interruption, through attempted deflection, by calculated bursts of anger designed to intimidate; to act in a disrespectful manner to authority figures, even those trying it earnest to help them; to continue with their bankrupt lifestyles while openly expecting others to pick up the tab; to have full freedom in such cases as they're in prison for having engaged either in domestic violence (including child abuse) or some other crime.
You know you're dealing with the best of our species, most worthy to reproduce, when he cannot tell you definitively how many children he has!
To the last man of them - and I have been in a position to meet far too many of these meatsacks - these guys have come into conflict with the law. The great majority are violent, thankless, and in a state to blame every person or thing they can except themselves. Few are gainfully employed.
These men are, in general, a reprehensible lot who should be offered money to undergo sterilisation before they afflict the world with more of their "reproductive success."
And very few of the women who find themselves pregnant by a 23-year-old man with 13 kids by 11 other 'babymommas' are all that bright either. A few will do right by their kids - or at least they try - but all the while never fully understanding why an unstable home situation could in itself hurt a child; how witnessing abuse, even if it's "only" aimed at their mother, will break the child's trust in authority.
"He never touches the children." Fah! If he mistreats you, he already is hurting your kids. It doesn't matter if they can see the altercation or not.
The resulting children are far more likely to break the law and also to perpetuate the cycle by which they were created.
Certainly many such children, when they become adults, develop the will and discipline to succeed. Many had met a teacher or a coach or some other adult who modelled respectful behaviour and also required it. (It might not seem like you can do much beyond small and kind gestures - greetings, a simply holiday card, a book you found useful - when you know a kid in a crappy situation. But they remember.)
To be clear, consenting adults could get high and spend weeks awake fucking each other blind in a debauched orgy where some of the participants drink vodka from each others' asses - aside...um, do NOT put alcohol up your ass; you could easily poison yourself - I personally do not care as long as everyone is having fun and no one gets hurt. It's that simple - and so is using birth control.
When people speak of dysgenics, they should be far less worried about when disabled persons in long-term relationships decide to have a child than about the various children of confusion borne to thoughtless, brainless parents.