Common origin for bugs and lobsters.

For more than a century, scientists have debated the family tree of the arthropods, the largest and most diverse division of the animal kingdom. Now, scientists have found genetic evidence that all arthropods--from the lowly millipede to the lobster--have a common ancestor. The discovery of a common genetic circuit for limb formation in arthropods not only is important for developmental biology, but also holds promise as an important new window to the past.

"This is a new way of looking at evolution. For arthropods, the fossil record has a lot of missing links," notes University of Wisconsin-Madison molecular biologist Grace Panganiban. "The record is not clear about what evolved into what. Here, at the molecular level, we can see the tracks of evolution."

Panganiban and her colleagues have discovered a common set of genes that govern limb formation among arthropods, a broad division of the animal kingdom that includes insects, crustaceans, spiders, centipedes, and millipedes. That finding, she indicates, constitutes new evidence that arthropods--which include tens of thousands of distinct species--arose millions of years ago from a single common ancestor.

The newly discovered genes...