Past Time

Past Time is a paleontology podcast about the evidence behind the history of life, and it rarely stays abstract for long. Episodes are anchored in things that can be pointed at: a paper, a museum specimen, a rock formation, a conference talk. Take the trilobites. In 'Episode 34 – March of the Trilobites', a study of 480-million-year-old trilobites from Morocco is read part by part. The conversation stops on the place name, because that Ordovician shale kept fine detail on each animal and also how the animals sat in relation to one another in life. Without that, there would be no behavior to talk about. The framing joke, that the first animals to work together formed a conga line, is silly. The point underneath it is not. The frog episode applies the same logic on a smaller scale. It centres on a single tiny bone at the Perot Museum of Nature and Science in Dallas. It gives real attention to microsites, which mostly preserve fossils small enough to fit on a fingertip, and to screen washing, where mud and rock are rinsed away until bones are left on the mesh. Other episodes take on a whole lineage and push back on a lazy assumption. Crocodiles, the show argues, are no living fossils. Their Mesozoic relatives included short-snouted plant-eaters, cat-sized forms with long legs, and large land carnivores. That episode then turns to growth and asks whether lineages that evolve slender snouts all get there by the same developmental route. 'Episode 33 – The Story of the Sloth' does the same for an animal famous for doing very little. It describes elephant-sized giants that may have walked on two legs some of the time, and a Pliocene lineage whose bones grew thick and dense as it became more marine, more manatee than dolphin. The sauropod episode begins as a scene: a house-cat-sized plant-eater drinks at a river 200 million years ago in what will become South Africa. Then it turns to a Current Biology paper by paleontologist Blair McPhee on a giant from the earliest Jurassic. Who is speaking varies. Adam Pritchard closes several episodes on his own, and Matt Bortz and Katherine Early join him for group conversations. An SVP recap brought in Garrett Kruger and Sabrina Ricci of the I Know Dino podcast, alongside talk of what appears to be fossilized dinosaur lung and of flat-headed pachycephalosaur specimens from the Hell Creek formation. The sloth episode is a good first listen. It asks for one thing: picture a sixteen-foot sloth as heavy as an elephant, and enjoy it.