I love writing about evolution’s great transitions–from water to land, from ground to air, and so on. For our species, one of the biggest of those transitions happened when our invertebrate ancestors became vertebrates–complete with our distinctive backbone, muscles, mouths, noses, and eyes. For fifteen years, I’ve been writing about this transition, and it’s been exciting to see more fossils come to light that help us understand how our inner fish got its start. For my new “Matter” column in the New York Times, I take a look at one of the most interesting of these fossils–what one scientist has dubbed a benchmark for our understanding of the first vertebrates. It’s called Metaspriggina, and here’s a video of an animated reconstruction. Get the rest of the story here.