In the old days, when a Mosuo girl turned 13, her family provided her with a windowed room on the second floor of the house, called the "flowering room".

When night fell a suitor would sing under her window, in order to win her heart.

When permitted, the young man would quietly climb through the window and spend the night there.

He would leave in the morning and work for his mother's family in the daytime, but return to his lover at night.

Today, a "walking marriage" usually happens when a girl reaches the age of 20. The relationship is based on mutual affection and ends when one of the couple wishes to separate.

Only when the relationship has ended peacefully, can the man or woman find another partner, otherwise they will be publicly denounced.

"Behind the walking marriage idea there is the concept of a big family, which is the core of Mosuo culture," says Aqi Nimacier, of the Lijiang Lugu Lake Mosuo Culture Research Association (MCRA).

Generally, the most senior grandmother is in charge of the family - which includes her daughters, sons and the daughters' children - and they live in the same household.

Uncles on the mother's side usually do light farming work.

"The concept of a big family narrows emotional distance among members of a Mosuo family," says Dazhu Cililachu, from the Museum of Mosuo Culture in Luoshui village, Yongning township.

"People are more charitable and less selfish and there are seldom conflicts among family members," Cililachu says.

Nimacier, a Mosuo man, says this puts a lot of responsibility on Mosuo men.

"We Mosuo men have responsibility for our sisters' children, although they are not born to us or our partner. In this way, we are more responsible" to the larger family, Nimacier says.