School principal Baast chose the name "Nomad" in keeping with his wandering spirit. Defense Minister Gurragchaa -- the only Mongolian to venture into space -- settled on "Cosmos." And anthropology student Vanchigdash picked the Mongolian word for "Wisdom." "It makes me feel rather wise," he said. "I'm very proud of my new name."

Mongolians, long used to using only first names, are reshaping their identities under a government-led initiative to add surnames.

For those who didn't give it much thought, and even some who did, the most obvious choice for a surname was, is and always will be Borjigin, the clan name of Genghis Khan, the 12th-century warrior and native son who put this Central Asian nation on the map.

"It seems like half the population is named after Genghis," said Ganaa, a 30-year-old mother whose family initially considered Borjigin before settling on Aldar, the name of their ancestral village. "It's good we're adopting surnames, because there's been lots of confusion. But with everyone choosing Genghis's name, that's also confusing."

The new hereditary system of surnames promises to create more historic continuity than the use of one name. So far, however, most Mongolians still don't use them, except on the most formal of occasions.

"To tell you the truth, I can't remember mine," said Odonbayar, a tanned 24-year-old herder from southwestern Mongolia.

First names worked reasonably well in an isolated, nomadic culture. But officials say surnames are now needed to avoid confusion in a more modern society, to help uncover long-buried roots as people delve into their clan histories and to prevent the sort of inbreeding that occurs when you're not sure whom you're related to.

Mongolia did once have family names. Local historians claim that the country was among the first to adopt them, citing clan-name entries in "The Secret History of the Mongols," a 13th-century text.

This tradition was ended, however, when Mongolian Communists swept to power in the early 1920s. Clan names initially were banned in order to improve tax collection. So many people at the time shared the same last name, said Lonjid, a Mongolian State University historian, that using your first name -- and occasionally your father's for clarity -- was seen as a way to make names more distinct.

Once in place, however, the surname ban stuck, in part because it suited Mongolia's often brutal Communist regime, historians say. By wiping out old clan names and destroying historic baggage, the revolutionaries hoped to stifle resistance by the former aristocracy -- so-called golden relative clans that traced their lineage to Genghis.

Mongolia first passed a law requiring surnames in 1997, but it was largely ignored until this year, when the names became necessary for a new government identity card. Now, more than 90 percent of Mongolia's 2.7 million people have adopted them, experts say. Holdouts tend to be herders and nomads in the country's more remote areas.

Many of those looking for help in choosing a name have turned to a how-to book written by Serjee, a linguist and director of the State Central Library of Mongolia. Look for local histories that might reveal your family or clan name, he advises from his cavernous office in downtown Ulan Bator, the capital -- although finding your original family name doesn't necessarily guarantee you'll want to use it.

"My research suggests most original Mongolian surnames were bestowed by neighbors in the village," Serjee said. "These include 'Thief' and 'Family of Seven Drunks.' "

If that fails, adopt a clan name specific to your area, he suggests, or use your profession, your home town, a nickname or something unique about your lifestyle.

"Be imaginative, be brave," he said. "Make up your own name. They may be new now, but in 50 years they'll be old."

The population-wide naming frenzy has led individuals to some unexpected discoveries. When Dorjnamjim, head of the Mongolia office of International Finance Corp., got together with family members to mull over their choice of surnames, he learned that his father already knew their original last name -- Urianhai -- but had kept it a secret.

Most Mongolians would immediately recognize Urianhai as the name of a Buddhist monk, part of a group particularly hated by Communists trying to wipe out religion. "If you were a monk, you were put to sleep forever by Stalin's Mongolian puppets," Dorjnamjim said.

Mongolia may be late to the surname game, but its reasons for adopting the practice now, which include a desire to avoid confusion and appear more modern, dovetail with the experiences of other cultures.

Throughout history, surnames have been adopted at different times by different cultures. One of the first references dates back to 2852 B.C. when a Chinese emperor decreed the use of hereditary family names. England, motivated by a shortage of first names, introduced them over a 600-year period starting around A.D. 1000. Japan made the push after 1870 as part of a modernization drive, and Turkey was as late as 1935. Some nations, including Indonesia and some Pacific Islands, still rely on one name.

In keeping with the pattern seen elsewhere, many Mongolians have relied on nature for their inspiration. Thus Oyun, vice speaker of the Mongolian legislature, uses a surname that translates as "descendant of Ulaalzai, keeper of blue falcons"; her husband has adopted the majestic "Mountain and the Sea."

In Mongolia, women keep their names after marriage, although it's expected that children will adopt their father's surname rather than their mother's.

Mongolia's drive to add surnames, whatever they may be, reflects a bid to reverse some of the social problems resulting from the overturned ban.

One of these has been unwitting inbreeding. Communist resettlement policies in the 1950s and '60s conspired with Mongolia's lack of surnames to boost intermarriage among close family groups, medical experts say.

Unfortunately, poverty and Mongolia's expanse -- it's larger than Germany, France and Spain combined -- have prevented detailed studies of the problem, they add, or the use of genetic testing.

"It was a very big mistake to stop using surnames," Purevdorj, head of the genetics department at the Health Sciences University of Mongolia, said as he leafed through grim pictures of deformed children. "Partly because of this, Mongolia's genetic structure is not in very good shape."

Choosing second names -- including the mad dash to name themselves after Genghis -- is also helping Mongolians reconnect with their history and rekindle national pride after decades of relative isolation. "A man who doesn't know his ancestors is like a monk lost in the woods," goes a popular Mongolian proverb.

History and genealogy were once pillars of Mongolian life. Those in the lower classes traditionally passed down oral records, while upper-class Mongolians kept family trees on silk or thick cloth that dated back generations.

"This isn't a fad. It's Mongolians finding their roots," said Leyton Croft, director of the Asia Foundation's Mongolia office. "There's a feeling that this is their historical right, and they're now going to exercise it."

A third reason for adopting surnames is to better adapt to the modern world. "If you live in the countryside as a nomad, you don't need a surname," said Munkh-Orgil, Mongolia's foreign minister, who has two words in his first name. "There's no need to keep a property registry or file judicial documents. But as a quarter or half of the population live in the city, you need surnames for mailing addresses and credit histories."

There's added pressure as more Mongolians travel abroad and get tired of explaining repeatedly why they only use one name. "There's a feeling for many that the rest of the world uses surnames and we need to look modern at a time of globalization," said Munkh-Erdene, a historian who also has a double first name.

Despite such reasons and the government's bid to make surnames stick, experts admit that the whole exercise is still a bit of a muddle.

Because they've been acquired so easily, many Mongolians hold little attachment to their new second names, reasoning that they can always change them later -- a relatively easy process.

Nor have families always been consistent. "Try to have all relatives use the same surname," Serjee advises. "Five children shouldn't have five different names."