However, sponges seem unlikely ancestors. They are little more than a loose assemblage of cells that lack the true tissues and organs found in higher animals. Plus their structure – a porous mass of interconnected water channels – is nothing like that of any other animal. As a result, most zoologists tend to put sponges on a side branch of the animal tree, an abortive experiment that led nowhere. That’s what makes Kevin Peterson’s results so thought-provoking.