The origin of the exquisitely complex vertebrate brain is
somewhat mysterious. "In terms of evolution, it basically pops
up out of nowhere. You don't see anything anatomically like it
in other animals," says Ariel Pani, an investigator at the
Marine Biological Laboratory (MBL) in Woods Hole and a graduate
student at the University of Chicago. But this week in the
journal Nature, Pani and colleagues report finding some of the
genetic processes that regulate vertebrate brain development in
(of all places) the acorn worm, a brainless, burrowing marine
invertebrate that they collected from Waquoit Bay in Falmouth,
Mass. The scientists were searching for ancestral evidence of
three "signaling centers" in the vertebrate embryo that are
major components of an "invisible scaffold that sets up the
foundation of how the brain develops," Pani says. Diagnostic
molecular features of these signaling centers are mostly missing
in the sea squirts and the lancelets, the invertebrate chordates
that are the closest evolutionary