She grew up in a matriarchal Himalayan society that frowned on marriage. So what's Namu doing living the high life in Beijing, asks Clifford Coonan.

You might expect a woman from a village in the foothills of the Himalayas, who grew up herding yak barefoot and drinking butter tea, to be shy, provincial. Yang Erche Namu is anything but that. Namu, as she likes to be called, is one of China's best-known writers. Before she lost her hearing in one ear she was a famous singer. She has strutted her stuff on the catwalk as a model and twice been voted the best-dressed woman in China.

This kind of versatility, and a glamorous lifestyle, make her a true child of the new China. "For our generation it's really different, because we don't really have any role models," she says, wearing her habitual designer clothes as we talk in a busy Beijing restaurant, where she seems to know everyone.

Namu is a Mosuo, from a matrilineal society, or "country of daughters", bordering Tibet that has no word for father, where families are run by the most senior woman and where monogamy and marriage are frowned on. She describes the remarkable circumstances of her upbringing in her most recent book, Leaving Mother Lake: A Childhood At The Edge Of The World, which she wrote with the anthropologist Christine Mathieu. It's a simply written book, with a clear style that gives the humour of her story room to breathe.

Her home is on Lake Lugu, the Mother Lake of the book's title, between the Chinese provinces of Yunnan and Sichuan, near the fabled area known as Shangri-La. About 50,000 Mosuo still live in the matriarchal way, she says, practising "walking marriage", where women pick their lovers and receive them in "flower rooms" to conceive children. The men return to their own homes before the sun rises, and the maternal uncles bring up the offspring.

Namu's mother took the unusual step of setting up home in a different village from the one in which she was born, so it was no big surprise that her third daughter - whom she tried to trade for a son because she cried so much - inherited a wilful spirit.

As a child Namu herded yak with her uncle before she was discovered as a singer and toured China. At 14 she ran away to Shanghai, where she earned a place at the city's conservatoire. She learned to read and write there too. Her travels eventually took her to San Francisco, where she added fashion model and nightclub bouncer to her curriculum vitae, then Geneva, where she assumed the role of a Norwegian diplomat's partner for many years. She describes the relationship as an "international walking marriage".

Now on her own again, Namu still juggles many roles - she is cultural ambassador for the Mosuo people, an activist for environmental protection and a television host, and she runs a guesthouse near Lake Lugu - but writing is central to her.

She still writes longhand, in Chinese characters, she says, showing me the callus on her index finger. "I write in a very funny way. I'm very lucky, because my way of writing is not the traditional way. I have no model, no influence; I write down the first sentence that comes into my head and slowly build up from there." Her belief in the importance of the writer's job is one that has become a little unfashionable in the West, but she believes her role writing books about self-help and guidance for a Chinese audience, with titles such as Namu Can Do, So Can You, is vital in contemporary, developing China.

"In the countryside I get young girls giving me eggs, chickens, spices, clothes they've made, because they've read my books; they say my books have helped them, and that makes me happy," she says. "People read my books because they like the way I'm thinking. They say, she's from a minority area, and she understands this, so why can't we?"

China still has a relatively prudish take on sexuality; predictably, the Mosuos' open relationships have attracted a lot of often prurient interest. But Namu insists that walking marriages do much to promote tolerance. "A lot of people in China think I come from free-love country. They say, hey, that's Namu, she's from the free-sex place. But in my culture we don't have hate. In my culture we call each other brother and sister; it's all family. When the sexual chemistry is gone we're still friends. Still friends because you know that at some time during your life you shared moments together."

She acknowledges that jealousy and deceit will always appear at some point in human relationships, but she says the Mosuo way does not allow these negative qualities to become institutionalised in the way she saw when she lived in the US, for example. "In California it was ugly. One day you see people saying you're the woman in my life, you're the man in my life, the next day they're fighting in court. It's really sad, ugly, hopeless," she says.

The Mosuo courtship ritual is straightforward. When a girl turns 13 she gets a flower chamber where she can receive her chosen suitor, whom she has picked out using various signals. When the boy arrives she can let him in or, if she changes her mind, hang his baggage outside the door.

"You know, a lot of corruption in China is because of mistresses. The men want something new - it's human nature - and young Chinese women know tricks about how to dry-clean a man's wallet, but in my culture you never see men and women fight, torturing each other."

Not that her background has prepared her for everything. "Living in the big city alone can be very difficult. Sometimes I just want to give up: marry someone, have 10 children with him, stay home. But when I think this way I go out and buy a pair of high-heeled shoes - and I feel ready to fight again."

Shoes have an emblematic role in her life. In Leaving Mother Lake the only gift she ever receives from her father is a pair of red corduroy shoes. In her later life high heels mark the transition to modernity. "I bought my first pair of high-heeled shoes back in 1988. I brought them back to Lake Lugu and walked in my village. I left them outside the door at night, and the next day the shoes were all dirty - all the girls in the village had tried them on. The shoes were too big to wear."

Namu is aware that the rapid pace of change in China could endanger some of the old traditions, particularly those minority traditions that she grew up with. But she is also clearly excited by the opportunities that the country's opening up brings and is focused on the possibilities offered by a richer, freer China. "In the 1960s and 1970s you couldn't do everything, because everything was controlled, but now you can do so many things."

Asked about rumours that she is unique in having appeared in both National Geographic and Playboy magazines, she says: "I was in National Geographic in 1991, but I never was in Playboy. If someone wants to put me in, though, give them my card! I'm the first yuppie Mosuo single woman living in Beijing. I've no time to date. I'm a five-star gypsy. My refrigerator has only coffee and milk and bread. I don't have holidays. I spent Chinese New Year by myself, writing. I'm no good at sharing."

She says she's fed up with lovers from the big city, whom she finds jealous, controlling, opinionated and even patronising. "When I go back to the lake I go walking and see friends. You know, I don't really like to eat that much in the city; it's scary: the food looks so beautiful, but you don't know where it comes from. But whenever I go back to my village I open my stomach. I eat; I drink 80 bowls of butter tea. I sit by the lake and read, talk to the people. I like my people, they're low key. They see me and just go, oh, you're back."

Leaving Mother Lake: A Childhood At The Edge Of The World by Yang Erche Namu is published by Abacus, £10.99 in UK