THE genome of the sea squirt, a distant cousin of animals with backbones, has been sequenced. It is helping reveal how the genome of vertebrates like us evolved.
Sea squirts, with their leathery, filter-feeding tubes, do not look much like long-lost relatives. But the larval form of sea squirts reveals their true ancestry. These free-swimming tadpoles have a stiffened rod, or notochord, running down their back, which in a developing vertebrate is the forerunner to the backbone. They also have a simple brain and heart.
The creature that gave rise to both sea squirts and vertebrates appeared on the planet…
