So was mine, so don’t feel too insulted.
Dr. PZ Myers of Pharyngula has written a wonderful piece on new evidence that the most recent common ancestor of all chordates (i.e. you, me, dogs, goldfish, lancelets, and sea squirts) was a sessile, seafloor-dwelling suspension feeder. This creature’s larva were probably lancelet-like fishoids, with a springy notochord (a precursor to the vertebrate spinal cord) and a simple tentacle-ringed mouth. At some point, in one of the ancestors of the vertebrates, one of the larva accrued a mutation that prevented it from reaching adulthood, and it maintained its fishlike body plan, eventually giving rise to true fishes, and later every other vertebrate.
I will attempt no further summary of the article. Read it. Read it now!
Once you’ve read Dr. Myers’ piece, please note this excellent song lyric posted by a commenter named Becca:
It’s a long way from amphioxus, it’s a long way, to us.
It’s a long, long way from amphioxus, to the meanest human cuss
cause it’s goodbye to fins and gillslits, and welcome lungs and hair
it’s a long long way from amphioxus, but we all came from there
(To be sung to the tune of “It’s a Long Way to Tipperary,” in case you hadn’t figured it out.)