The woman's mother comes by and brings a gift -- of plump and tasty cooked yams. They eat these together. The following day, the guy's family arrives with gifts of clothes: skirts, long skirts for his girlfriend. Because if they're going to be a real couple now, it's time to get rid of the wild, wanton wardrobe she wore as a teen.
Then more people from the woman's family arrive, relatives of each of her parents. These folk bring uncooked yams, raw material for many meals to come. Then the man's family comes by with a Bed, Bath & Beyond's worth of cookware, knives, and curios. And then these relatives receive gifts from the bride's relatives -- more yams, uniting all the families in one glorious yam union.
Yams: like gold and jewels, except their value isn't totally made-up.
If the woman gets tired of the relationship, she just moves out, and, boom, she's single again. Her ex can try and win her back with more gifts (deluxe yams?), and if she accepts them, they're again married. But if she doesn't, they aren't.
These relaxed attitudes may come from how the Trobriand, following their traditional lore, didn't think men fathered children. Children were thought conceived when spirits entered the mother's head. The man's semen merely nourished the fetus. This Spunk of Sustenance theory may also be why Trobriand boys were encouraged to ingest lots of semen during adolescence ... but that's a subject for another article. Or, not.