The Human Factor
LEIPZIG, GERMANY--Svante Paabo lopes through the Leipzig Zoo, his long legs carrying him swiftly to the new ape house. "These are the orangutans," he says, reaching toward the glass to mirror the hand that a shaggy orange ape has extended on the other side. "They really like to go up to people. The gorillas ignore humans; they can kill each other. And the bonobos [pygmy chimps] have no violence, ever, and lots of sex." This visit isn't just a walk in the park. The ape house is also a laboratory, part of the Max Planck Institute for Evolutionary Anthropology, which Paabo directs here in the former East Germany. It's here to help answer a question he's been chasing for the past 25 years: What makes humans human?
For answers, Paabo, 47, is looking at DNA--from humans, from a long-extinct human relative, and from chimpanzees and gorillas like those at the zoo. He's even sought clues in 2,000-year-old human feces from a Texas cave. His finds have shed new light on how we became so different from our closest ape relatives and are offering tantalizing clues to great mysteries that remain, such as the origin of language. "Svante is going to be the first anthropologist to win a Nobel Prize," says Richard Klein, an archaeologist at Stanford University. "He just comes out with one paper after another that seems to be a breakthrough in human evolution."
Paabo first gained wide public notice in 1997, when he and Matthias Krings, a fellow researcher at the University of Munich, sequenced DNA from a 40,000-year-old piece of Neanderthal bone. The DNA was so different from that of modern Europeans that it quashed long-held theories that Neanderthals, the heavy-boned inhabitants of ice-age Europe, were our ancestors. Neanderthals apparently did not even interbreed with the humans who arrived in their territory 40,000 years ago.
Teamwork. That same year, Paabo got a chance to go after bigger questions when he was named director of the new Institute for Evolutionary Anthropology. It's an unusual effort, not only because it brings together DNA experts like Paabo with linguists, primatologists, and psychologists but also because of its lavish resources--a $9.4 million annual budget, $17 million for the ape center, and a $37 million new headquarters, set to open February 12. The cash comes as part of Germany's ongoing reunification efforts, but the interdisciplinary collaboration, many say, comes as a result of Svante Paabo.
As a boy growing up in Stockholm, Paabo dreamed of sailing south to explore the tombs of ancient Egypt. But when he started studying Egyptology at the University of Uppsala in the late 1970s, he was crushed to learn that it demanded not expeditions to the pyramids but memorizing hieroglyphic verb forms. "It wasn't cool." So he started studying medicine, his father's profession, and molecular virology.
Then he realized that Egyptian mummies and modern patients had something in common--DNA. Mummy DNA was cool. His old Egyptology professor helped him gather samples from museums. Working secretly, nights and weekends, he became the first to isolate ancient human DNA. In 1985, still a graduate student, he published a paper on his feat in Nature and sent proofs to Allan Wilson, a pioneer in molecular genetics at the University of California-Berkeley. "I got this message: `Dear Professor Paabo, can I come do a seminar in your lab?' " Paabo, floored, wrote back: "I'm not a professor, I'm not a doctor, I don't have a lab, but can I come to you?"
Wilson's lab was the first to show that DNA from living humans could be used to trace the origin of modern humans back to Africa. It was also one of the first in the world to use PCR, a chemical process that made it simple to copy DNA a billion times over, turning a mere trace into enough to study. Paabo had not been able to analyze the mummy genes, but with PCR, he believed, ancient DNA could open a direct window into the past--looking tens or even hundreds of thousands of years back.
With PCR, Paabo was able to duplicate DNA from extinct animals like the quagga, a type of zebra, and the moa, a flightless bird, swiftly answering long-standing questions about their relationship to living animals. Other extinct creatures followed, including mammoths, ground sloths, and cave bears. With Michael Hofreiter and other graduate students, he has also extracted DNA from the feces of ancient animals and humans, revealing much about their diet, behavior, and environment.
But in coaxing DNA from 40,000-year-old Neanderthal bones, Paabo may have pushed ancient DNA as far as it can go. Old DNA is hard to find; its nucleotides degrade when exposed to water, oxygen, and heat. "I've looked at something like 270 samples," says David Serre, a graduate student who spends long hours testing bits of Neanderthal bone cadged from museums and universities. "Only 20 of them still contain DNA." Worse, modern human DNA is on everything we touch. It can easily mislead researchers. Spectacular claims--such as one that Chinese researchers had extricated DNA from a dinosaur egg--were proved false when closer analysis revealed that the molecules were merely modern contamination. "It's rather embarrassing," Paabo says, rolling his eyes.
A relative. With ancient DNA giving just narrow glimpses into the past, Paabo is turning to what could grant a wide-angle view--the genes of the great apes. Chimpanzees, our closest cousins, share 98.7 percent of their DNA with humans. The trick is to find what in that 1.3 percent difference accounts for the things that make Homo sapiens special--language, reasoning, MTV. The chimp genome is being sequenced in labs around the world. When it's done, in 18 months or so, it should be a powerful tool for understanding how the species diverged.
For now, Paabo is fishing for another kind of difference. He is comparing patterns of gene activity in ape and human tissues to learn where genes are switched on and off. "We find so many differences, which is surprising," says Wolfgang Enard, a graduate student. "They are particularly pronounced in the human brain." The group has also found that methylation, a process that can adjust gene activity, is more prevalent in the human brain, suggesting it is a more finely tuned instrument. And last year, Enard found a key difference in the human and ape versions of Foxp2, a gene that was recently found to be essential for human speech. Mathematical analysis suggests that the human variation cropped up about 200,000 years ago, which could be about the time speech emerged.
To pin down the essential differences between the minds of apes and humans, the institute's researchers are also trying to identify what we have in common. Primatologists are studying culture--once thought to be exclusive to humans--among wild chimps in Africa. Psychologists are watching the baby chimps at the Leipzig Zoo and their drooling human counterparts in town. "For the first 10 months you can't tell the difference between chimps and humans," Paabo says. "Then the human children realize that behind your eyes is something that they can direct. That there are other people like me." Perhaps those children, too, will someday ask what makes a human human.
In Short
"Chimps and humans are so similar."
BORN April 20, 1955, Stockholm
FAMILY Twelve people, a dog, and a cat, in a shared house in Leipzig
EDUCATION Ph.D. in molecular immunology, 1986, University of Uppsala
LANGUAGES Fluent in Swedish, German, English. "It's a little bit easier for me to write in English and in German--it depends on the subject."
HOBBIES Rock climbing. He practices on a climbing wall in his institute's new building.
This story appears in the January 20, 2003 print edition of U.S. News & World Report.