In the shadow of a granite mountain in remote Yunnan, on the shores of a lake shaped like the shell of a gourd, live a tribe that the rest of China has dubbed the Kingdom of Women.
In the matriarchal tribe of the Mosuo, one of the last of its kind on earth, women call the shots. Bloodlines pass through mothers, while fathers are often little more than sperm donors. It is the women who inherit land and property, choose lovers as they please, and raise the children from these alliances.
Singaporean Choo Waihong spent six years living with the Mosuo. She documents the experience in a new book, The Kingdom Of Women: Life, Love And Death In China's Hidden Mountains.
Speaking over the telephone from London, where she is on a book tour, she says of the society on the shores of Lugu Lake: "It's a place where I can imagine what a man must feel like in a man's world."
Once a high-flying corporate lawyer, she decided to retire in 2006, leaving behind the 15-hour work days and the "boys' club" world of law firms in Singapore.
She made up her mind to quit in a period when she found herself constantly at work on Sundays with no end to the routine in sight.
One Sunday, she was driving home from work after midnight when a bus trying to beat the red light rammed into her car.
"I wasn't hurt, though the car was quite badly damaged," says Choo, who declines to give her age. "But I could have died."
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She soon resigned, packed her bags and took off for her grandfather's village in China to connect with her roots, a trip which evolved into a grand tour of the country.
Along the way, she read in a travel magazine about the Mosuo's worship of a mountain goddess called Gemu, which so fascinated her that she dropped everything and headed for Lugu Lake.
Over subsequent visits, she befriended the locals, had a traditional Mosuo house built and ended up godmother to an entire village.
Although she is based in Singapore, Choo, who is single, continues to spend about half a year with the Mosuo, sometimes helping with the harvest and waitressing at her friend's restaurant from time to time.
She describes it as a "feminist utopia", worlds away from her old workplaces in Singapore, where male colleagues felt entitled to make sexist remarks and being vocal about her opinions would earn her comments such as "Oh, there she goes again, doing her woman thing".
That the matrilineal system of the Mosuo continues to exist, she notes, is especially incredible in patriarchal China, where a preference for male children has skewed the gender ratio to nearly 120 boys for every 100 girls, and unmarried women over the age of 27 are considered "leftover".
Instead of marriage and the nuclear family, the Mosuo practise "walking marriage". They take lovers, or axias, with whom they have sese, sexual liaisons which could take the form of a long-term relationship or a one-night stand.
If children are born from the relationship, they are raised by their mother's family and their father has no claim on them. The typical Mosuo home is occupied by three generations of women, ruled over by the grandmother, with male axias coming and going.
Choo recalls overhearing a conversation between her Mosuo friend Erchima and her family about the division of land, including a plot on which Erchima's axia Zhaxi had a guesthouse. Asked what Zhaxi had to say about this, Erchima replied: "He has no say in this matter. He is not family."
Choo notes with regret that the concept of sese has often been misinterpreted by outsiders as promiscuity, even though the Mosuo are themselves private about sex and do not openly discuss it.
"Bus drivers and tour guides make walking marriage into a joke," she says. "It does draw the tourists, who hope they'll get a slice of action, but it doesn't respect their customs."
The old ways of the Mosuo are themselves under threat, as tourism jobs and the cash economy lure more and more young people away from a life of subsistence farming in sleepy hamlets.
Choo recounts how she has seen more and more of these young people get married instead of having sese, as matrilineal family units split up into separate households.
Although she believes Mosuo culture will not be utterly eradicated, especially in the smaller inland communities, she feels it would be a pity to lose it.
She hopes her young goddaughters will retain their confidence in their womanhood, even as they ease further into Han Chinese society.
"I believe the Mosuo women are strong enough to say, 'I demand the same thing of you that you demand of me.' They start from a position not of weakness, but of strength."
•The Kingdom Of Women: Life, Love And Death In China's Hidden Mountains ($42.35) by Choo Waihong is available at Books Kinokuniya.