The Common Descent Podcast

Check the fingers and toes of your favorite vertebrate animals and you’re likely to find claws or something similar at the ends. These digit-caps come in a variety of shapes – claws, nails, even hooves – for a variety of functions. In this episode, we discuss the close relationship between claw form and function, how we study claws in the fossil record, and the intriguing questions of how claws ca...

You’re probably familiar with frogs and salamanders, but there is a third group of modern amphibians, the strangest of them all: the worm-like caecilians. In this episode, we’ll explore the many bizarre anatomical features of caecilians, from their tentacled faces to their abrupt hind ends. Then we’ll explore the entire caecilian fossil record (it won’t take long) and tackle the much-discussed mys...

We spend a huge portion of our lives sleeping. For us and other animals, it’s clearly a very important behavior. And yet, despite how familiar and commonplace it is, there’s plenty we still don’t understand about sleep: its origins, evolution, and even how to define it in the first place. In this episode, we explore some of the remarkable variation in animal sleeping habits, we discuss some of the...

Once, it was a volcanic crater. Then, it was a lake, perhaps equal parts lush and deadly. Much later, it was a mining site. And finally, today, it is a UNESCO World Heritage Site and one of the most famous and heavily studied fossil sites in the world. In this episode, we discuss the history and formation of the Messel Pit, and we ooh and aah over a small sampling of the many thousands of incredib...

Giraffes are so famous and familiar to most of us that it can be easy to forget how utterly strange they are. This episode, we explore modern giraffes, their living cousins (okapis!), and their ancient relatives to understand how these monumental mammals came to be how they are. Along the way, we’ll meet a whole variety of wacky-horned fossil species, and we’ll tackle the questions of how and why...

Happy Darwin Day! You’ve seen his artwork. And if you somehow haven’t, you’ve seen lots of art inspired by his artwork. Charles R. Knight might be the most influential paleoartist of all time, inspiring a century’s worth of artists, scientists, and ancient-animal-enthusiasts around the world with his skillful and scientifically-informed works. In this episode, we explore who Knight was, how he bec...

Glowing organisms might seem like something out of science fiction, but not only do they exist here on Earth, they are incredibly common. Some species glow when exposed to certain kinds of light, and others produce their very own light in the darkest habitats on the planet. This episode, we explore glowing life: how they do it, what they use it for, and what we can tell about how this remarkable a...

The Paleozoic Era was home to many strange and fascinating extinct groups, and among the most eye-catching of these were the eurypterids. Colloquially called “sea scorpions,” these carnivorous aquatic arthropods came in many forms for many habitats and are now known from many amazing fossils. In this episode, we discuss what makes eurypterids distinct from similar organisms, what we know about the...

Happy New Year! It’s been an exciting and eventful year for the podcast, and we’re glad you’ve been along for the ride! As usual, this is our annual Q&A where we answer the many, many questions our listeners submitted – the scientific, the silly, and the personal. Thanks as always to all of our listeners, our Patrons, our special guests, and to everyone who supports the podcast in ways big and sma...

It’s a great time of year to talk about conifers! Also their cousins: cycads, ginkgos, and others! Gymnosperms don’t get nearly as much love and attention as their flowering counterparts, the inescapable angiosperms, but they nonetheless have their own fascinating history going all the way back to some of the earliest forests on Earth. This episode, we’re joined once again by our favorite paleobot...

Viviparity is the reproductive style where embryos develop inside a parent’s body instead of inside an egg the parent lays. It’s a very familiar habit to us placental mammals, but it’s also an extremely widespread and diverse feature of life. Seriously, it’s ridiculous just how many times viviparity has evolved and just how many different ways species have found to be viviparous. In this episode w...

Built-in body armor is common among reptiles and rare among mammals, but armadillos are the major exception. Equipped with a full set of segmented armor over their heads, backs, and tails, armadillos have been waddling around well-protected for tens of millions of years, and their ancient relatives include some of the most famous and preposterous of extinct mammals. This episode, we discuss the un...

You might have noticed that over the last few decades, a lot of really exciting and famous fossil discoveries have been coming out of China. If you pay close attention, you might even catch that many of them are coming from the same place: the incredible fossil assemblages of the Jehol Biota. We’ve mentioned Jehol fossils many times on the podcast, but in this episode, we focus on the big picture:...

Look at the various animals on Earth – or rather, look just behind them – and you’ll see a vast variety of tails! Tails and tail-like structures are often simple extensions of the body, and yet they’ve been adapted and modified into many shapes with many functions, and because they’re often so important to an animal’s lifestyle, they can be especially useful for paleontologists trying to understan...

Welcome ... to Spookulative Evolution. October is here, and that means it’s time for Spook-E! Each episode throughout this month, we’re choosing a monster and discussing how it – or something like it – might evolve under the rules of evolution and natural selection, pulling inspiration from organisms of the real world. This year’s theme: monsters of Dungeons and Dragons. This episode, we delve int...

Welcome ... to Spookulative Evolution. October is here, and that means it’s time for Spook-E! Each episode throughout this month, we’re choosing a monster and discussing how it – or something like it – might evolve under the rules of evolution and natural selection, pulling inspiration from organisms of the real world. This year’s theme: monsters of Dungeons and Dragons. This episode, we gaze upon...

Stegosaurus is one of the all-time most famous and recognizable dinosaurs, but it wasn’t alone! Its whole extended family, the stegosaurs, were medium- to large-sized herbivorous dinosaurs sporting an array of plates and spikes. This episode, we discuss the diversity and deep history of stegosaurs, what we know of their lifestyles, and of course the big questions: just what were they doing with th...

Welcome ... to Spookulative Evolution. October is here, and that means it’s time for Spook-E! Each episode throughout this month, we’re choosing a monster and discussing how it – or something like it – might evolve under the rules of evolution and natural selection, pulling inspiration from organisms of the real world. This year’s theme: monsters of Dungeons and Dragons. This episode, we roll out...

Welcome ... to Spookulative Evolution. October is here, and that means it’s time for Spook-E! Each episode throughout this month, we’re choosing a monster and discussing how it – or something like it – might evolve under the rules of evolution and natural selection, pulling inspiration from organisms of the real world. This year’s theme: monsters of Dungeons and Dragons. This episode, we play with...

In our modern world, ants are so ubiquitous that it’s difficult to image our planet without them, so successful that they shape the environments around them despite their tiny size, and so diverse that we couldn’t possibly discuss even a small fraction of their diversity in this one podcast episode. We’ll touch on some of what makes ants unique, list a few of our favorite examples of modern ant li...

Powered flight is hard, and evolution has only produced it a few times. Gliding, however, is much easier and much more common. In fact, there is an astonishing diversity of gliding organisms to be found in our modern world as well as in the fossil record, with an incredible variety in the adaptations they use to sail through the sky. This episode, we’ll explore what it takes to glide and what patt...

For many years, scientists pondered the question: how and why do offspring inherit traits from their parents? And key to the answer to that question is another question: what determines an organism’s traits in the first place? The pursuit of these answers ultimately led to the modern field of genetics, which itself is crucial to the study of evolution. This episode, we address just a few key point...

Every period of geologic time is distinguished by its own environmental and ecological features, and every boundary between time periods is characterized by change. The boundary between the Jurassic Period and the Cretaceous Period is mostly marked by mystery. Was there a mass extinction? Were there catastrophic changes? Where even is the boundary exactly? In this episode, we’ll discuss the answer...

We live in a solar-powered world. Photosynthesis is the process by which some organisms (notably plants and cyanobacteria) harness the energy of sunlight to power their own metabolism, in the process creating the sugars (food) which provide a source of energy for all sorts of other organisms, not to mention releasing oxygen as well. Photosynthesis is the reason our planet is the way it is, from th...

The history of evolution is full of species of unusual size, big and small. But the factors that lead to evolutionary miniaturization or embiggening can be quite varied and are not all fully agreed-upon by scientists. This episode, we discuss what it means for life to evolve huge or tiny, what trends researchers have identified in body size evolution, and which of those trends actually holds up to...