Chimpanzee or orangutan? Which great ape is our closet kin?

The debate rages.

The predominant opinion, based on genome comparisons, settles squarely on the shoulders of the chimp.

But University of Pittsburgh anthropologist Jeffrey H. Schwartz refuses to ape the chorus of popular doctrine.

In a recent study published in the Journal of Biogeography, he and John Grehan, director of science at the Buffalo Museum, produce fossil evidence that identifies our closest relative as the placid, arboreal red ape -- the orangutan.

It represents an in-your-face refutation of the chimp camp in modern-day paleontology, evolution and anthropology. To advance the primate metaphor, the article has prompted strong opposition from the chimp camp, which accuses the orang camp of monkeying with scientific certitude.

"As far as I know, and I know Jeff well, and we are friends, he and John Grehan are the only two scientists on the whole planet who subscribe to this red-ape hypothesis," said Todd Disotell, an anthropologist with New York University's Center for the Study of Human Origins. "I think he is utterly, factually wrong."

Drs. Disotell and Schwartz are taking the orangutan harangue to an unlikely center stage: "The Daily Show" with Jon Stewart recently interviewed them for an upcoming segment.

Supporting the orang link, Drs. Schwartz and Grehan point to anatomical similarities between humans and orangs, including enamel molars, similar hairlines and shoulder blades, and even the ability to smile with lips closed. Even our skulls and eyebrow bone structure more closely resemble the orang's than the chimp's or gorilla's dramatically ridged eyebrows.

Drs. Schwartz wrote the 1986 book, "The Red Ape: Orangutans and Human Origins," that he updated and revised in 2005. Recently, he and Dr. Grehan produced "robust evidence" supporting their orangutan hypothesis.

The persistence by the Pitt anthropologist has prompted some doubters to suggest more study is necessary before either theory is dismissed or embraced. The latest study even drew reluctant praise for casting doubt on an accepted scientific belief.

The magazine New Scientist said in an editorial that it "applauded the effort to challenge traditional scientific belief."

Ian Tattersall, of the American Museum of Natural History, said the study should not be dismissed out of hand.

"I think that the general scientific unwillingness even to consider the notion that orangutans are more closely related to us than African apes is testimony more to the power of received wisdom than it is to the power of the evidence."

Drs. Schwartz and Grehan defend their hypothesis with fossil evidence -- morphological evidence -- to suggest that humans, orangutans and early apes belong to a different hominid group than chimps and gorillas.

The argument begins with translation of the word "orangutan" -- from Indonesian and Malaysian words for person (orang) and forest (hutan). Dr. Schwartz says humans share 28 anatomical characteristics with orangutans, compared with two with chimps and 11 with gorillas.

Besides hairlines and teeth, humans and orangs have a single hole in the roof of the mouth, while chimps and gorillas have two holes. Dr. Schwartz also says intelligence tests prove that orangutans are the smartest of the great apes. The orang is known to study a situation and learn through observation before putting a plan into action.

On the other hand, chimps and gorillas tend to lose their cool and resort to brute force and sometimes hysteria when confronted with a puzzle, such as how best to get food out of a container or stack boxes to reach bananas hanging from the ceiling.

Shared anatomical characteristics, intelligence quotients, similarity in brain structures and the strong resemblance between orangs and humans all support the orangutan hypothesis, Dr. Schwartz said. "Orangutans in their reproductive behavior and physiology are more like us."

Adding to the controversy, Drs. Schwartz and Grehan claim that movement of apes over millions of years through Asia, Eurasia and Africa also links humans to orangutans rather than chimps or gorillas.

But Dr. Disotell counters: The last 10 million years of evolution has seen humans evolve from African apes -- and chimps, in particular. That explains why he tells his students that people are African apes.

Evidence produced by the chimp camp is based on more than 98 percent similarity between the human and chimpanzee genomes. That compares to a 97 percent similarity with the gorilla and only 96 similarity with the orangutan genome.

Dr. Schwartz said the DNA argument is flawed and overlooks the workings of RNA rather than DNA in making valid comparisons. (Both are nucleic acids found in human cells. While DNA material makes up genes and chromosomes that carry the genetic blueprint that controls our bodies, the RNA acts as a messenger carrying out instructions from DNA) He also said comparisons are based on only about 2 percent of the genome -- a point Dr. Disotell says simply is not accurate.

In response to the recent pro-orangutan article, Dr. Disotell said, he's writing a critique with a graduate student that counters Dr. Schwartz point by point. With the genomes on his computer, he said results clearly reveal that orangs split from the human course of evolution 13 million years ago while the chimp split about 6 million years ago.

"In the last two days, I've generated a mini data set of 12 billion bases," Dr. Disotell said. "It takes a lot computational effort, but each produced the same result. The orang branches off first. The human and chimp are most related."

So the ape debate reduces to molecular and DNA analysis vs. fossil and physical characteristics. Which leads to one final point-counterpoint before we put this monkey business to bed.

"He is remarkably canny in getting publicity on this because it is a controversial topic," Dr. Disotell said. "I think he's completely wrong on this hypothesis of his, but I have his books on my shelf."

Dr. Schwartz shrugs off the criticism, acknowledging that his theories have even been described as nonsense.

"Others have said worse," he said. "When humans share a feature with another animal, it almost always is the orangutan."