The question that what sets humans apart from other animals has been settled by scientists who have mapped the complete chimp genome and compared it to the human gene map.

Differences in the sequence of four chemical "letters" that spell out the genetic codes, or genomes, of chimp (Pan troglodytes) and man (Homo sapiens) could account for the very human abilities to write novels or fly to the Mars.

"As our closest relatives, they (chimpanzees) tell us special things about what it means to be a primate and, ultimately, what it means to be a human at the DNA level," Dr. Francis Collins, head of the National Human Genome Research Institute, which funded the studies, told a news conference.

The comparisons of the two genomes, published on Wednesday in the journal Nature by 67 researchers in the Chimpanzee Sequencing and Analysis Consortium, provide clear confirmation of the common and recent evolutionary origin of humans and chimpanzees, as first predicted by Charles Darwin in 1871.

Dr. Robert Waterston, one of the leaders of the international research team, from the University of Washington in Seattle and colleagues sequenced the DNA of a chimpanzee named Clint, who died last year of heart failure at the relatively young age for a chimp of 24, but two colonies of his cells have been preserved for future study.

They compared it to the human genome sequence and did a letter-by-letter comparison of the DNA base pairs -- the A, C, T and G nucleotides that make up both the human and chimp genetic codes.

Out of 3 billion base pairs that make up both the human and the chimpanzee genomes, only 40 million differ between human and chimp, they found.

"Within those 40 million differences are clearly the genetic bases of what makes us human." said Dr. Waterston.

Genes usually code for proteins, the molecules that build and operate a body, and many key differences are expected to be found in genetic code that controls where proteins are made, how and in what quantities.

The chimpanzee is only the fourth mammal to have its genome sequence completed, after humans, rats and mice, though a draft is available for the dog. Of these species, humans and chimps are by far the most similar. The differences between them are ten times fewer than those between mice and rats, and sixty times fewer than those between humans and mice.

But, added Collins, the study did not address philosophical or religious questions.

"It may very well not tell us about other aspects of humanity, such as how do we tell right and wrong," Collins said.

Source: Xinhua/agencies