BERLIN — American and German scientists yesterday launched a twoyear project to decipher Neanderthals’ genetic code, a feat they hope will help deepen understanding of how modern humans’ brains evolved.

Neanderthals were a species of the Homo genus who lived in Europe and western Asia from more than 200,000 years ago to as little as roughly 30,000 years ago.

Scientists from Branford, Conn.-based 454 Life Sciences Corp. are teaming up with Germany’s Max Planck Institute for Evolutionary Anthropology to map the Neanderthal genome, or DNA code.

“The Neanderthal is the closest relative to the modern human, and we believe that by sequencing the Neanderthal we can learn a lot,” said Michael Egholm, the vice president of molecular biology at 454, which will use its high-speed sequencing technology in the project.

There are no firm answers yet about how humans picked up key traits such as walking upright and developing complex language. Neanderthals are believed to have been relatively sophisticated, but lacking in humans’ higher reasoning functions.

The Neanderthal project follows scientists’ achievement last year in deciphering the DNA of the chimpanzee, our closest living relative, which produced a long list of DNA differences with the chimp and some hints about which ones might be crucial.

The chimp genome “led to literally too many questions, there were 35 million differences between us and chimpanzees — that’s too much to figure out,” 454’s chairman, Jonathan Rothberg, said in a telephone interview.

“By having Neanderthal, we’ll really be able to home in on the small percentage of differences that gave us higher cognitive abilities,” he said. “Neanderthal is going to open the box. It’s not going to answer the question, but it’s going to tell where to look to understand all of those higher cognitive functions.”