When David Evans and Allen Counter first journeyed a few years ago 200 miles into Surinam's interior, deep into the Amazon bush, they encountered Djuka tribesmen in a setting that looked like West Africa of the 1700s.

The tribesmen asked Evans, 38, senior admissions officer at Harvard, and Counter, 34, a Harvard biology professor, if they had found the road home. Not quite, but the pair thought they had found a remarkably preserved imprint of Africa's ancient past.

The music and language, religious customs and agricultural techniques were African. But these people lived in the northern part of South America.

They were descendants of abducted Africans who were brought to South America in the 1600s but defeated their Dutch opponents after a century of warfare and carved out their own settlements in the bush.

The tribesmen have lived outside white domination and carried on life much as their ancestors had done for hundreds of years. They still ask the rain forest's permission" to cut down a tree. They fallen trees. They use herbs to cure ills. And their village life is communal.

"We like to think of it as a very powerful chapter of Afro-American history," says Evans. "We have gone back in our history and looked at what our people were like."

For the researchers, the psychological lesson is clear. Says Evans, "This example should be held up to all the brothers at 14th and U, in Detroit, Watts. It shows that we have not always lost."

The pair say there are other lessons. While scores of black Americans have traveled to Africa recently (in the wake of publication and subsequent TV production of "Roots") in search of their past, Evans and Counter say the Djuka are living examples of what Africans were before slavery.

A film of the Evans and Counter trip will be shown tonight at 8 on Channel 26. "I Sought My Brother," a 90-minute documentary, is narrated by James Earl Jones. Also, Alex Haley, the author of "Roots," interviews Evans and Counter in segments interspersed throughout the program.

The film shows the tribes living in thatched huts, wearing sparse, colorful clothing and fishing for piranha.

Evans and Counter lived among these villagers in the summers of 1974 and 1975 and for brief periods in 1972 and 1976.

Their impressions are still strong. "I do not like living in the jungle," Counter insists. "There were poinsonous snakes, tarantulas, which weren't poisonous but their bite could put you off your feet for a day, and parasites in the water. We had to be careful of where we bathed in the river. Also, there was the danger of piranha in the water."

Counter, who's currently on sabbatical from Harvard conducting research in neurophysiology at the Korolinska-Nobel Institute in Stockholm, also says he missed restaurants, movies, television.

The villages are isolated from city life. The settlement can be reached only by canoe because the jungle growth is too thick to cut through.

Counter first learned of the Djuka while at a scientific meeting in Brazil in 1970. After returning to Harvard and reading old, rare books about the tribes, he was eager to visit the Surinam bush. But he had trouble finding anyone to go with him.

"Most people thought I was crazy," he recalls, "Ninety-nine percent of black people hadn't heard of the bush people. Most whites hadn't either. But once David started looking at those rare books, he got hooked."

The two decided to make a film record, according to Evans, because. "We felt it was our responsibility to bring something back to black people. We're not anthropologists. We make a point of that."

They showed the film to the Djuka in 1976. "These people had never seen a film before," explains Evans. "At first they were afraid. They stood way back from the screen. But the children broke the ice when they saw themselves and recognized playmates.

Soon everyone settle down and watched.

"It was funny. After watching it, they flipped from being first-time filmgoers to editors, directors. They told us, 'You can't cut a tree down in three minutes. It takes three hours,' Or, You can't travel from one point in the river to another in minutes. It takes hours.'"

The two men are writing a book about the bust tribes. Counter, who conducted hearing tests on them, is moving ahead with ethnopharmacological tests on the Djuka.

"They have a thorough knowledge of medicine," contends Counter. "These people have plant medicines most people never heard of. They extract a substance from a leaf and use it to induce abortions. Some of the nearby Indian tribes use the same leaf. That's how many women kept from having babies by white plunderers."

The Djukas, says Counter, know they're from Africa. When a group of tribal chieftains went on a Surinamess government-sponsored tour of West Africa in 1971, they recognized many customs similar to their own.

Evans and Counter showed their film to Francis Boaten, Ghana's ambassador to the United Nations, and he wept, saying the Djuka had preserved customs lost to the Ghanains for 200 years.

How long can they hold on to their way of life? Not long, say Evans and Counter.

"They're changing," notes Evans. "Their crops are failing. Game is disappearing. The government is considering building a highway through their settlements."

Says Counter: "Industry is already displacing animals so that they're dense in some areas and sparse in others. But there is resistance. Some of the older people are breaking up boats, not letting the young people leave the villages. And as urban life encroaches, some of the Djuka are moving farther into the bush."

But industrial society presses on. "One of the last things we saw before leaving," recalls Evans, "was somebody giving a buy a bicyle - and he couldn't even ride it!"