Deep in the heart of downtown Bombay, a century-old blue-granite building stands like a silent sentinel to an ancient community in rapid decline.

The dilapidated building houses the Parsi Lying-in Hospital, established in 1893 as a maternity unit for the city's once-thriving Parsi community. Built to accommodate 40 beds, its wards are almost empty today. "We get only four or five patients a month," says Zarin Langdana, the doctor-in-charge. "And most of them are not Parsis."

As India's population expands steadily, the country's Parsi community faces extinction. Emigration, falling birthrates, the growing tendency to marry outside the community, and an injunction against accepting converts is threatening to erase Zoroastrianism, the world's oldest prophetic religion, and its followers from the map of India. "We are an endangered species, just like the tiger and the lion," says Jamshed Guzdar, chairman of the Parsi Panchayat, or council.

A recent demographic study predicts that by 2021, when the population of India will be 1.2 billion, the number of Parsis will drop from their current level of 60,000 to just 21,000.

Bombay legacy

Parsis once dominated Bombay's commercial life. Almost every major municipal building built in the 19th century had the bust or statue of a Parsi benefactor perched on a pedestal outside. Parsis started the city's first hospital, university, and municipal corporation. The city's best-known landmark is probably the Taj hotel, built by Jamshetji Nusserwanji Tata in 1903 after he was refused entry into the exclusive Green's Hotel because he was a native.

Mr. Jamshetji's great-grandson Ratan controls India's largest industrial conglomerate, the Tata group. "Now the Parsi population's outlook has changed," laments Mr. Guzdar. "There is no urge to step forward and create for themselves high positions in business and industry. Now they find they cannot meet the competition."

For most communities, the prospect of extinction would unite members, but it has divided the Parsis. In Bombay, the world's Parsi "capital," the gulf between those who refuse to question orthodox Zoroastrianism and those clamoring for reform is breaking apart a once close-knit community.

Perhaps the most divisive issue is whether the children of a Parsi woman who marries outside the community can be considered Zoroastrian. "It's a very emotional issue," says Jehangir Patel, editor of the monthly magazine Parsiana. "As the community gets smaller, your chances of finding a Parsi spouse to your liking are dwindling. More and more families are being touched by this problem."

Questioning Zoroastrianism

With almost 1 in 4 women marrying outside the community and almost as many not marrying at all, the mixed-marriage bias is being challenged. "People are questioning the faith much more," says Smiti Crishna, vice chairperson of the Association of Inter-married Zoroastrians. "The religion has to undergo a change in order to protect and propagate the community."

A member of the wealthy Godrej family of Parsi industrialists, Ms. Crishna broke the taboo on intermarriages when she wed a Christian businessman. According to the orthodox keepers of the faith, her two daughters cannot undergo a navjote, or baptism ceremony, or enter a Zoroastrian fire temple. "Women like us are ostracized," Crishna says. "Why should people look down on us when there is no injunction against intermarriage in our holy books?"

That's wrong, retorts Dastur Firoze Kotwal, one of the religion's eight high priests, who leafs through a religious text in his south Bombay flat. According to Dastur Kotwal, the Zoroastrian scriptures outlaw all intermarriages. He also dismisses demands that the ban on conversions be lifted to swell the community's numbers, a stand that has put him at loggerheads with the normally conservative Parsi Panchayat. "Zarathustra never said you can't convert. If you don't allow conversions, how does the community grow?" asks Guzdar of the Parsi Panchayat.

Alarmed by the steady demographic decline of the Parsi population, Guzdar persuaded the Panchayat to sponsor the third child of every Parsi couple to encourage larger families. The Panchayat now looks after the material and educational needs of 45 children. "I thought to myself, I cannot let my community perish," Guzdar says. "I hope that by doing something like this, the population will increase."

A successful businessman who established India's first air freight business in the 1940s, Guzdar plans to set up a venture-capital fund to encourage young Parsi entrepreneurs to start businesses in India rather than moving abroad.

The disappearance of the Parsis would not just be a loss for Bombay. This small but talented community has produced composers like Zubin Mehta, novelists like Rohiton Mistry, and the late rock star Freddie Mercury, the former front man of the band Queen. "Last year when I was asked to become the chairman of the National Foundation for Social Affairs and Family Planning, I was told, 'Do all you can to control India's population but make sure the Parsis increase in number,' " chuckles Guzdar.