An international team of scientists Wednesday announced the first comprehensive comparison of the genetic blueprints of humans and chimps, an effort that explains what makes us so similar to our closest living relative – yet so strikingly different.

“The differences shed light on our uniqueness,” said Dr. Eric Lander, director of the Broad Institute of Cambridge, Mass., and one of the principal investigators of the project.

The insights will contribute to medicine, because many of the differences relate to disease susceptibility.

Humans die from illnesses like malaria, AIDS and Alzheimer’s disease, while chimps are immune.

They could also explain other evolutionary changes that caused the species to diverge – and gave humans the ability to walk, talk, use tools, ponder the future and build giant societies.

The genetic sequences of the most important parts of the human and chimp genomes are about 99 percent identical, according to the analysis by 67 researchers, including a team from the University of California-Santa Cruz.

Part of the chimp genome is not shared by humans; part of the human genome is not shared by chimps.

When the genomes of the two species are compared more broadly, including non-functional “junk DNA,” they are 96 percent identical.

While this sounds like a close connection, people are far more closely linked to each other, the scientists explained. There is only a 0.1 percent difference between individual humans – in other words, there are 10 times fewer differences between all humans than there are between humans and chimps.

Humans and chimps shared a common ancestor 6 million years ago, then parted ways. How we changed, and why, has long intrigued scientists.

The DNA differences will offer clues to the mysteries of aging and disease.

The genome comparison finds some of the most dramatic differences in regions thought to cover the immune system. This would explain varying susceptibilities to disease. Other regions, such as those governing the nervous system, seem very similar.

As scientists compare genomes more closely, they will seek genetic “outliers” in individuals – patterns that do not conform to those in the general population. This would suggest a unique trait, such as susceptibility to a rare disease.

The analysis also depicts evolutionary change. It shows that chimp and human genomes have changed over 6 million years, because of selective pressures of their different environments, said Dr. Robert Waterson, chairman of the Department of Genome Sciences of the University of Washington School of Medicine in Seattle.

“I couldn’t imagine Darwin hoping for stronger confirmation of his ideas than this,” Waterson said.