With the traditional nuclear family well on its way to extinction, we are faced with a question of critical importance: who will mind the children? Neither two-career nor single-parent families offer children full-time, loving caretakers, and quality day care is both scarce and expensive. Nanny's are a luxury out of reach for most families making up the 99 percent. Even at its best, full-time institutional care (including public schooling) cannot provide the individual attention, intimacy, flexibility, and opportunity for solitude that children need to realize their potential. Serial monogamy presents children as well as parents with a stressfully discontinuous family life. Meanwhile, an entire generation is at risk, as divorce is increasingly common fact of life.
While we don't yet know how polyamory impacts the rate of divorce; the little data we have suggest that it doesn't. Some people have begun to joke about "serial polyamory," and it may turn out that any kind of lasting relationship is simply less likely in the 21st century. We do know that practicing polyamory can help prepare parents to maintain family ties after a divorce because the issue of becoming jealous when confronted with a former mate's new partner has usually been dealt with already.
Group marriages*can mean a higher standard of living while consuming fewer resources. Intimate partners are more likely than friends or neighbors to feel comfortable sharing housing, transportation, appliances, and other resources. Even if partners don't live communally, they frequently share meals, help each other with household repairs and projects, and vacation together. This kind of cooperation helps provide a higher quality of life while reducing individual consumption as well as keeping people too busy to over-consume. Multiple partners also help in the renewal of our devastated human ecology by creating a sense of bonded community.
Group marriage*may help provide siblings for children who would otherwise be lonely, only children. It can offer childless couples a low tech solution to the ever more common challenges of infertility. Multiple adult families can soften the ticking of the biological clock by providing older women the opportunity to raise and mother children conceived by a younger sister-wife. At the same time, polyamory helps overcome the apparent design flaw which mismatches ideal age range for pregnancy (20's) with ideal maturity and energy level for parenting (40's). As indigenous peoples know, it takes a village to raise a child!