Sure, you can love a child with whom you share not a speck of DNA. However, there's a real biological drive behind spreading your own genes. That, and no one likes being fooled.
Well, Western society dictates that paternity is important, but that is just a belief that was useful when woman and children were considered property.
I learned a little bit about the Na culture in China through a scholarly review on JStor of the book,
A Society without Fathers or Husbands: The Na of China (I have not bought the book yet). Very interesting people. This is from the review (publication is
American Ethnologist):
The Na have shocked Han Chinese ethnologists by not having marriage; rather, they practice visiting relations -- consensual sexual relations in which both partners remain members of their natal households and never form an economic or social union recognizable as marriage. Na men visit their partners in the evening and return home by morning to mothers, aunts, uncles, and siblings, to join in their own household's work. Either partner can end a relationship at any time, and both can take other lovers during or between longer-term relationships.
In Na matrilineal households, the father is considered socially unimportant, and, prior to the Na's inclusion in the communist state, his identity was often unknown. The Na share an understanding, albeit flexible, of the family as the blood or adopted members of the household; they see the family as central to their emotional, economic, and social existence . . . it is because the Na believe that families should be stable and harmonious that they do not base family structure on romantic relationships. These Na say that love for family members is enduring, whereas passion is fleeting.
The Na live in a way that shows how unimportant it is to know whose seed the children come from. It doesn't mean the men are not important to the culture, just that it doesn't matter which children are theirs.
The Na live communally and the men don't rule the households nor have any ownership over the women or their offspring, because they don't even know who they've fathered. That information is not integral for the community to thrive and function well, nor for any of the children to be loved, cherished, and raised well. The women who have children raise them with the help of their siblings, and family is preserved that way.
Familial ties are matriarchal. The women's brothers are uncles to their sisters' children, and help raise them. No one goes around asking who fathered those children. The father of one women's children would be living with one of
his sisters, and helping to raise
her children, while his offspring is being raised by their mother and her brother(s).
Too many people in contemporary so-called "advanced" society are focused on paternity issues. Millions of children are waiting to be adopted, yet couples will focus (and spend tens of thousands of dollars) on fertility drugs and artificial insemination just to make sure their bloodline continues. If anyone wants to love and raise a child, why limit that love to biological offspring only?
The Na's system enables a separation between familial love and sexual love/passion, which frees the adults to take on as many lovers as they wish without recrimination. I think it's a great model for communal living, if you're the type that wants one big happy poly tribe cohabiting. It would be daring, and probably legally tricky in certain aspects, but a very brave endeavor in our modern culture!