Humans are complex despite fewer genes than expected, most of them shared with other species.
Scrambling to unlock the secrets of the human genetic code, researchers stand on the kind of scientific threshold that appears once every century or so. They're poised to understand the forces behind evolution, explode racial myths, change the way doctors diagnose disease, and try to help people live longer.
But the first mystery along this long road of scientific discovery boils down to this: If man is so advanced, how come his gene count doesn't look that much different from a weed's or a worm's?
The question is forcing scientists to reevaluate their notions of biological complexity and mankind's place in the natural order. "At a basic level, I can assure you we're a lot more complex than worms," says Robert Waterston, director of the genome sequencing center at Washington University here in St. Louis. "The question becomes: How do we account for that complexity?" In this week's issue of Nature, Dr. Waterston and his colleagues at the publicly funded Human Genome Sequencing Consortium reveal that humans possess roughly 32,000 genes. In a separate article to be published in this week's edition of the journal Science, researchers at the privately funded Celera Genomics Corporation also confirmed that the human genome contains between 26,000 and 39,000 genes. That's far fewer than what many scientists were predicting only last year when, in one of science's great rivalries, Celera and the consortium rushed to publish rough drafts of the entire human genome sequence.
That string of biological code proved so long - some 3 billion units - scientists had expected it to contain instructions to create anywhere from 50,000 to 140,000 genes. Instead, they have discovered that vast stretches of the code create very few genes.
So what makes us complex?
"It appears that the human genome does indeed contain deserts, or large, gene-poor regions," writes Craig Venter, president of Celera, and 282 other authors in the Science article. Furthermore, just over a third of the human genome contains repetitive sequences that scientists label "junk DNA" because, at the moment, they don't appear to have any function. Researchers will spend coming months taking a deeper look.