4 ideas
Nia is a woman of a furred alien people whose men leave the village at adolescence and live alone. She is cast out of her matrilineal village because she kept up a lasting attachment to a man, a bond her society treats as perverse. She then wanders with the human anthropologist Lixia as a guide, and her outsider status lets her see her own culture's rules as rules rather than nature.
In Nia's people's society, males leave the matrilineal village at adolescence and live as solitary wanderers who find each other's company hard to bear, and the sexes meet mainly in a seasonal mating period. Village life, kinship and child-rearing are organized around groups of related women rather than around a co-resident husband. The novel also follows exceptions, such as Nia's attachment to a man, which her society treats as perverse, to probe how far those norms hold.
When an observer finds a society where love between a man and a woman is shameful and fatherhood is barely recognized, the categories she brought, such as marriage, family and romantic love, stop looking like universals. They become local inventions. The observer's reactions of discomfort, sympathy or judgment become data about her own culture rather than neutral measurements of the other.
Even a careful, non-interfering expedition changes the people it studies. Its technology, its questions and its mere existence alter what they believe is possible. The ethical question is therefore not whether to influence them but how much, and who gets to decide. That leads the explorers to seriously weigh withdrawing so the contacted people can choose the terms of any future relationship.