Sponge larvae: Your unlikely ancestors

This is the larval form of the sponge Plakina, and is nothing like the adult. Might something like it have been our distant ancestor?    CALL it CSI: Precambrian. About 700 million years ago, one of the most significant - and most mysterious - events in the history of life on Earth occurred. Suddenly, there was more to life than just single-celled microbes. Within a few tens of millions of years, an extraordinary array of large animals appeared, armed with jaws and claws and eyes and brains.   Yet we still know surprisingly little about the origin of multicellular animals. "The different branches of the animal tree evolved very rapidly in a short period, a long time ago," says Nicole King, an evolutionary biologist at the University of California, Berkeley.   The very first animals left few fossil traces. What they did leave were lots of descendants. It is to these descendants that evolutionary detectives have to turn to reconstruct the events of those early years. By comparing the genes of living organisms and painstakingly working out their family trees, they are slowly building up circumstantial evidence and piecing together a sketch of that first animal, our great-to-the-nth-grandmother. And not just its appearance - the detectives are also coming up with a motive, a reason why animals evolved when they did.   See how it happened: Six steps from single cells to complex animals   Full article here - New Scientist

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