Photograph by Evelyn Hockstein/Polaris, for The New York Times

Rock art sites in remote locations like Mfangano Island are attracting visitors. More photos

KAKAPEL, Kenya - There are two markedly different manmade etchings on a rock face here, and it is hard to decide which is the more jaw-dropping.

One, dating back thousands of years and featuring the outline of an elephant, is a sign that this hilltop in western Kenya was a special gathering place for early Africans. The other, no more than a few years old, featuring the names "DENNIS" and "PATRICK," is a sign that Africa's rock art is under threat.

Whoever carved those names seems to have disregarded the site's status as a cultural treasure. Authorities responded to the defacement by erecting warning signs and metal fencing around the rock face and declaring it a monument. But that has not stopped numerous copycats from slipping under the bars and scrawling their names into posterity.

Rock art has been discovered - and defaced - the world over. In the United States, a man was arrested in Utah last year for writing "I love you, Wendy" on a sandstone wall bearing ancient American Indian drawings. In another case, three stolen pieces of Indian rock art were recovered in 2003 from the front yard of a Nevada home, after being taken there in violation of the federal Archaeological Resources Protection Act.

But in Africa, there is a lack of oversight at many of the rock art sites, leading experts to offer a grim prognosis for their future. "It's very endangered," said David Coulson, the founder and chairman of the Trust for African Rock Art, a preservation group that sponsored a conference on the problem in Nairobi last fall. "Populations are rising so fast, and sites that were in wild, uninhabited areas have development growing around them. So you have graffiti, the single biggest threat."

Experts have long traced or photographed rock art images so they will at least be remembered once they are gone. The rock art trust has built a digital photographic archive of many of the fast-fading images, said Mr. Coulson, a photographer who has documented rock art in more than 20 African nations.

And lasers are being used to record rock engravings in three dimensions. The trust will sponsor an expedition early next year to record the "Fighting Cats" in southern Libya, a spectacular site that has existed for thousands of years but is in danger of crumbling into the surrounding sand.

Efforts are also under way to educate people who live among the ancient art about the value of the sites. Last year, the trust organized a well-received exhibition of rock art at the Nairobi National Museum that ran from November to February. The display, featuring photographs of rock art from throughout Africa and a simulated rock shelter, later traveled to Dar es Salaam, Tanzania, and went on view Sept. 15 for a three-month run at the Uganda Museum in Kampala.

Most rock art, however, is seen in the field. The rock art sites across Africa may number in the hundreds of thousands, experts say; their paintings and engravings, some 10,000 years old and perhaps much older, are spread over vast areas, often in inhospitable terrain.

The most striking sites in the Sahara and in southern Africa, once known only to locals, are now being discovered by outsiders. For example, getting to a little-known site in Kenya, a place not normally associated with rock art, requires a boat trip to Mfangano Island, one of the tiny isles in sprawling Lake Victoria.

A long hike up a rocky hillside eventually leads to a cornfield. Beyond that is some rocky terrain; off to the left, behind a makeshift gate put up by locals to protect the art, is a hidden shelf of rock bearing odd, circular symbols.

"If this goes, it means our culture is gone," said Jack Obonyo, director of the island's museum. "We would lose our identity. I would still be Jack, but I am also an Abasuba, a descendant of my ancestors who painted this." Mr. Obonyo, whose efforts to protect Kenya's rock art received help recently from a $29,500 American State Department grant, spins a colorful tale of what Mfangano Island residents believe the concentric circles, spirals and sunbursts mean.

He recounts a long-ago battle between the Abasuba people and rivals from another island. As the rival Wasaki moved in, the Abasuba women stood at the hilltop rock shelter at Kwitone dressed as men, frightening away the advancing warriors. The symbols were painted in celebration.

Unlike the rock art buried deep in caves in southern Europe, African art was painted and etched on rock faces far more exposed to the elements - and the public. Looting of the treasures also seems more commonplace. Early explorers of Africa chipped away the rock paintings and carted them off to museums.

Such looting still occurs, carried out by private collectors and their middlemen. Niger has dispatched guards on camels to patrol its farflung desert sites, but the area is so vast that they cannot possibly keep a close eye on the art. Morocco is another nation where vandalism has been fierce.

"The most barbaric thing we've ever seen was in Morocco, where thousands and thousands of 5,000-year-old engravings are bashed and broken off and taken out of the country," Mr. Coulson said. "It's an organized trade."

He said he had heard of galleries in London and New York selling illegal rock art at astronomical prices, with a small piece fetching $10,000 or more.

"For us, these sites have a spiritual, almost religious feel to them," Mr. Coulson said. "It's almost sacrilege to deface them."

Rock art enthusiasts do not want the sites completely fenced off from the public. When a gate was removed recently from the well-known White Lady of Brandberg site in Namibia, experts generally approved. The site is so known because early explorers mistook the male figure for a white woman and speculated that Africa's rock art was the product of foreigners. Careful scrutiny of the heavily faded image shows that it is a local bushman, however, experts say. Now, the 30,000 tourists who visit the site annually are kept back by a railing, and guides monitor the crowds.

The African rock sites often still play a role in local communities. Experts have found food offerings outside painted sites in Zimbabwe and learned of church services and traditional circumcision ceremonies at sites in Kenya and Tanzania.

In the Air Mountains of Niger, thousand-year-old life-size engravings have been retouched by locals in recent years, something that experts tend not to regard as typical defacement. One theory is that the engravings, on a still-used caravan route, were recolored to reactivate the power of the original images and protect modern-day caravans.

Of course, even those who no longer believe in the spiritual powers of the images may treasure them.

"I don't worship the pictures like my ancestors did, but I give them respect," said Mr. Obonyo, admiring the rock symbols on Mfangano Island at close range one recent day but taking care not to touch them. "It makes me proud of who I am."

Copyright 2005 The New York Times Company. Reprinted from The New York Times, THEARTS, of Saturday, October 8, 2005.