The Common Descent Podcast

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...

Happy Snake Month! In this bonus episode, we discuss snake conservation and geek out about snakes with special guest Hiral Naik of Save the Snakes. We talk about what it takes to save snakes, why snakes are so worthy of our attention and respect, and why education is such a major part of snake conservation! Follow Hiral on Twitter: @HiralNaik25 Instagram: @hirals_hive Save The Snakes:  https://sav...

Monitor lizards are charismatic, surprisingly diverse, full of surprising biological features, and on top of all that, they include the largest terrestrial lizards in history. Also, they’re closely related to snakes (it is Snake Month, after all). That’s a cool group of lizards! In this episode, we discuss what makes these lizards so unique and fascinating, and we dive into their long but often my...

Take a walk along the waterways of the Late Triassic, and you could easily think it was a world full of crocodiles! But in fact, those are not crocs, but phytosaurs, a group of predatory reptiles that represent not only one of the oldest groups of carnivorous reptiles to achieve a near-global distribution, but also one of evolution's most famous cases of convergent evolution. So, what features did...

Once again, we return to the Jurassic franchise! And as usual with these movies, there’s lots to discuss about the portrayal of ancient animals, scientific concepts, and scientists. Another trilogy concludes – Jurassic World: Dominion (2022) _ IT’S CROC MONTH! Check out our Croc Month activities on our social media, Discord, and Patreon! Check out our blog for bonus info and pictures: http://commo...

Happy Croc Month! In this special episode, we talk croc conservation and geek out about crocs with special guest Dr. Marisa Tellez of the Crocodilian Research Coalition. We learn about what it’s like to study crocs in the wild, we discuss the importance of public education, and we hear some of Marisa’s amazing croc tales! Follow Marisa on Instagram and Twitter: @crocparasites13 CRC Info: Webpage:...

Perhaps you’ve heard of Pangaea, the supercontinent that existed when our modern continents were puzzle-pieced together. But have you heard of Rodinia? Or Columbia? Scientists have only come to realize in the last few decades that supercontinents are a recurring feature of our planet. This episode, we discuss what counts as a supercontinent, what evidence they leave behind, and the various ways th...

Recently, BBC Studios put out a new documentary series set in the world of the Late Cretaceous, so we’re doing our first-ever Silver Screen Science discussion focused on a documentary! The documentary in question: Prehistoric Planet. Happy Croc Month! Special things are going on throughout this (and next) month in all the places linked below! Join us on Patreon to support the podcast and enjoy bon...

Who doesn’t like a flashy bit of headgear? A wide variety of cranial ornamentation is found on a wide variety of animals: sharp horns, branching antlers, bumpy knobs, and more. In this episode, we break down what technically counts as a “horn” (you’ll be unsurprised to learn there isn’t a simple answer!), the vast diversity of animal headgear today and in the fossil record, and the various ways an...

Scavenging isn’t easy. There’s a reason most scavengers are only part-time carrion-eaters. But vultures are exquisitely adapted for a dedicated lifestyle of finding and feasting on carcasses, and as a result, they’ve made themselves invaluable members of ecosystems all over the globe. In this episode, we explore vulture evolution, their ancient history, and the adaptations that make them the world...

It's an easy mistake to think of the Moon as a simple accessory to our planet, but the Earth and Moon are a close-knit pair, and the Moon influences everything from our tides to our magnetic fields to the brightness of our nights. All life on Earth has evolved in the presence of the Moon, and so life on Earth can't be fully understood without considering our cosmic companion. In this episode, we d...