But if cancerous tumors are not our great-grandparents, these guys most certainly are. Also known as the comb jelly, ctenophores first emerged 700 million years ago. They look like striped jelly blobs that flit through the sea propelled by rows of cilia. Biologists say these are the oldest known animals — and not sea sponges as previously believed — meaning we’re actually descended from these things. And most remarkable of all, as a living fossil, they’re still kicking around.