Three years ago, Ken Kosik, a Harvard Medical School neurologist who studies Alzheimer disease, packed up files and equipment from his lab in Cambridge and moved 5,000 kilometers west, to the University of California, Santa Barbara. There, he settled into a new laboratory, where he hoped to extend his focus from clinical research into the basic evolutionary questions about the origins of nervous systems, which had always interested him.
Where to start? Kosik consulted Todd Oakley, an evolutionary biologist at UC, San Diego, who suggested the sponge. On the tree of life, cnidarians (such as jellyfish and anemones) branched immediately after the sponge ancestor. Since cnidarians have a nervous system, the researchers reasoned that sponges - which lack organs, nerves, and complex tissues - might carry the molecular, evolutionary rudiments of synapses.
The number of sponge species is estimated at about 6,000, including finger-like, bright orange sponges, massive interwoven fans, ...
