Imagine for a moment that you've just come down from Mars and you're trying to understand Canada's laws on child support and custody.

You read a famous case that says the children of a broken family have the right to as high a standard of living as either of their parents.  You look at some statistics and you learn that on average, men earn more than women.  This gap is especially pronounced after marriage, and even more so after divorce.  

"This is simple," you think.  "The obvious thing to do is to let most children from broken families live with their fathers where they can enjoy a higher standard of living."

You continue reading through more family law decisions, and you learn that a common complaint of separated and divorced Canadian wives is that they've been disadvantaged by their family responsibilities.  They've lost career opportunities, experience, contacts and seniority.  

"This fits in perfectly," you think.  "These long-suffering women should be allowed the chance to make up for lost time in their careers.  Why not relieve them of the burden of child-rearing and let the children go live with their fathers?  That would also have the effect of putting some of the men on the ‘daddy track' at their jobs and smoothing out the wage gap between the sexes that feminist groups are always complaining about."

Then you read some studies about the problems suffered by children from single-parent families.  You learn that the girls are more than twice as likely as the daughters of intact families to get pregnant during their teens.  Both girls and boys are more than twice as likely to drop out of high school.  You also learn that the overwhelming majority of children in single-parent families over the past few decades have been living with their mothers.  

"Gee," you think, "mothers haven't been doing such a great job of raising kids on their own.  This seems like another reason to try letting the children of broken marriages live with their fathers.  They couldn't do much worse."

You discuss your conclusions with an Earthling friend who happens to be a family law practitioner.  He chuckles at your naiveté.

"Maybe your Martian courts make practical, realistic decisions like that," he says, "but when I tried making arguments like yours in the early years of my practice, the judges looked at me--no offence intended--as if I came from Mars.  Most of them believe children belong with their mothers, and that's all there is to it.  I've even heard some of them announce this openly in the courtroom.  The bias is so well-known that most men don't even attempt to get custody of their kids.  Why waste a huge chunk of the family wealth litigating a lost cause?  So mothers usually get custody of the kids, and we force fathers to give money to the mothers." 

"But does this system work well?" you ask.

"Not really," the lawyer admits.  "If your kids need a three-bedroom home to live in, it's a lot nicer to be the parent who gets to live there with them than to be the parent who pays for the house while living in a bachelor apartment.  If you have to put food on the table for your kids, it's more fun being there to eat it with them than it is to supply grocery money to your ex-wife.  Let’s face it: a lot of child support money gets spent in ways that are of considerable benefit to the mothers.  

"It's especially irritating for men if the wife was the one who decided to leave the marriage in the first place, or if she moves away so that dad hardly ever gets to see the kids.  After the tax collector and the ex-wife each take a slice off the top, there's not much incentive left for a man to keep slugging away at a difficult job.  So a lot of men resent having to pay support, even though they love their kids and would be glad to support them if they could get to live with them."

"Well, if the judges won't be practical," you suggest, "maybe the mothers themselves will be.  Maybe someone should point out to divorced women the benefits to the kids and to themselves of letting the kids live with dad."

"Are you joking?" the lawyer replies.  "Most women fight like enraged grizzly bears to keep their kids out of dad's hands.  Once they're through with a man, they think he's an irresponsible moron, even though he was good enough to marry, good enough to live with for several years and good enough to procreate with--not just once, but in many cases two or three times.  Then these women frequently go out and get re-married—to some other woman's cast-off irresponsible moron.  But let the kids live with dad?  Never."

You climb back into your space ship and return to Mars, disappointed that you have once again failed to find intelligent life forms elsewhere in the universe.