|Acorn worm / Image credit: NOAA Okeanos Explorer Program, INDEX-SATAL 2010|
In an effort to discover the characteristics we humans supposedly inherited from organisms found in the Cambrian explosion, scientists have sequenced the genome of the acorn worm. “It's an ugly beast,” says UC Berkeley professor John Gerhart, leader of the project. Coauthor Daniel Rokhsar boldly claims, “Acorn worms are marine invertebrates that, despite their decidedly nonvertebrate form are nevertheless among our closest invertebrate relatives.”To read the rest, head on over to "Seventy Percent of Human Genes Traced Back to Acorn Worm?"
“Acorn worms look very different from chordates, which makes it especially surprising that they and chordates, like humans, are so similar on the genomic, developmental and cell biological levels,” Gerhart adds. Chordates include humans and other vertebrates as well as a few invertebrates, but not acorn worms. Chordates, if only as an embryo, have a bundle of nerves like a spinal cord supported by a cartilaginous notochord, a body that extends past the anal opening, and a series of openings in the side of the throat (pharyngeal slits). Reflecting the evolutionary presumptions that guide his interpretation of genetic comparisons, Gerhart says, “I'm interested in the origins of chordates, which, of course, came from non-chordates, and hemichordates like the acorn worm are the closest we have to this lineage. So it’s important to compare the development and genomes of our group, the chordates, with the hemichordates if you want to know what characteristics the common ancestor really had.”