Biologists Studying Flatworms Discover an Early Case of Bilateral Symmetry

A team of biologists last week concluded that an unusual group of flatworms is the oldest living ancestor of all animals possessing bilateral symmetry -- that is, having roughly symmetrical left and right sides.

The researchers, from the University of Barcelona, in Spain, and the Natural History Museum, in London, published their findings in the March 19 issue of Science.

The first multicellular animals

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