Humans' closest cousins, the Neanderthals, vanished 30,000 years
ago after sharing turf with humans for millenniums. But why they
disappeared remains a mystery.
Two research teams decided to try a new approach: Instead of
studying tiny fragments of DNA from one of these cousins, they
looked for ways to string fragments together to get a more complete
source of potential genetic clues. Conventional wisdom held that
this task was impossible for material this old. But using the 38,000-
year-old remains of a 38-year-old male, found in a Croatian cave,
each group now says it has rebuilt, or sequenced, long segments of
Neanderthal DNA - the twisted, ladder-shaped molecule in the nucleus
of cells that holds an organism's genetic blueprint.
The technique is not only yielding new insights into
Neanderthals, reported in Thursday's issue of the journal Nature and
Friday's issue of Science, it's also likely to prove an important
tool in teasing out secrets about how plants and animals evolved,
researchers say. DNA "is the ultimate forensic record of evolution,"
says Sean Carroll, an evolutionary biologist at the University of
Wisconsin-Madison. "There's never been a more exciting time to be an
Within the next two years, one team hopes to finish a rough draft
of the Neanderthal's full genome. This would help scientists answer
nagging questions about the Neanderthals' evolutionary history,
including factors contributing to their demise. It also would yield
insights into the evolutionary history of modern humans.
"We are at the dawn of Neanderthal genomics," says Dr. Rubin,
with the US Department of Energy's Joint Genome Institute in Walnut
Creek, Calif. He likens the effort to those of archaeologists who
deciphered hieroglyphics to learn about ancient Egyptians in detail.
The results that will be published this week are "really a big
teaser," says Anne Stone, who heads the Molecular Anthropology
Laboratory at Arizona State University. But it's an important one,
she adds. The sequences the two teams have produced cover 65,000 to
1 million base pairs. Each base pair is built from four basic
chemicals that make up an organism's genetic "code." Each base pair
forms a "rung" on the DNA molecule's ladder. By comparison, the
human genome, and presumably the Neanderthal's, consists of some 3
billion base pairs. But the DNA strands that the teams have strung
together are far longer than any previous length of Neanderthal DNA.
The samples are based on DNA in the cell nucleus. This DNA
carries contributions from a father and a mother. …