Who is man's closest relative?

Until recently most scientists have been saying, "It's probably the chimpanzee." They based this in large part on the behavior of chimpanzees, and a close relationship between the genetic material of chimpanzees and humans.

Yesterday a Columbia University geneticist said, "It's probably the gorilla."

"The race is close - some people favor the chimpanzee, some the gorilla." Dr. Dorothy Miller conceded. But she said that new studies of human, gorilla and chimpanzee genes establish the hulking gorilla as man's closest primate relation.

She also said that now a few scientists have begun observing the gorilla more closely and starting to try to train gorillas as well as chimps to communicate with humans. "We're gaining a lot more respect for the gorilla intelligence," she said.

Miller summed up her views in the latest issue of Science magazine. She also cited a recent report in the British journal Lancet by an Edinburgh team that found a close resemblence between gorilla and human semen.

Anthropologists generally think the apes and man had some common ancestor, and millions of years ago the line of evolution split, with one branch slowly leading to modern man and another to the monkeys and apes.

Actually, all of these lines of evolution had many splits and branches. But Miller, based on her studies and other evidence, thinks the gibbon (a tailless ape of southeast Asia) may have split off from the more or less direct main line that led to man 28 million or 29 million years ago.

The orangutan apparently split away 18 million years ago and, Miller believes, while the chimpanzee made its split about 13 million years ago and the gorilla only 10 million or 11 million years ago.

"Evolutionarily, the gorilla and chimp are both very close to us," Miller explained. And different scientists have used different ways to look at the various species' genetic makeup.

What she did was place gorilla, chimpanzee, human and other primate chromosomes - strings of genes - on slides. Then she used various chemicals that either cling to or stain certain parts of the chromosomes.

The chemcials divided the chromosomal material into light and dark areas in band-like patterns, largely based on the chromosomes' chemical composition.

The banding of gibbon and organgutan chromosomes was nothing like that of humans, she found. But the banding of chimpanzee and gorilla chromosomes was close to humans, with gorrilas' the closer.

She said in an interview that humans have left close to chimpanzees in part because "it's been a lot easier for the behaviorists to observe chimpanzees than to observe gorillas." Also, she said, chimpanzees are much easier to handle, therefore easier to train, therefore more "human-like" to casual appearances.

"But I also have a feeling," she said, "that gorillas are more introverted and chimpanzees more extroverted," meaning they like to do things that attract human interest.

"You can see adolescent gorillas play games and throw things at you like chimpanzees," she reported. "Then when they grow up, they more easily become more morose."