Mammal Brains Got Smaller During First 10 Million Years After Asteroid

About this episode

Steve Brusatte, paleontologist at the University of Edinburgh and consultant on Jurassic World films, traces the complete evolutionary history of dinosaurs and their descendants in this comprehensive interview. Brusatte begins with the Permian extinction 250 million years ago, the worst in Earth's history, which killed 95% of all species when Siberian supervolcanoes triggered runaway greenhouse warming. From the survivors emerged small reptiles that would become dinosaurs. He explains how dinosaurs remained second-tier players for tens of millions of years until another mass extinction at the end of the Triassic wiped out their crocodile competitors, allowing dinosaurs to dominate. Brusatte corrects popular misconceptions about T-Rex, revealing it could only run 10-15 mph contrary to Jurassic Park depictions, had arms the size of human arms despite being bus-sized, and likely had feathers. Most controversially, fossil evidence proves many dinosaurs, including tyrannosaur ancestors, were covered in feathers. The asteroid that struck 66 million years ago created a nuclear winter lasting up to a decade, killing everything larger than a husky dog on land. Only small beaked birds survived among dinosaurs because they could eat seeds during the prolonged darkness. Brusatte's research on mammal evolution reveals that mammal brains actually got relatively smaller in the first 10 million years after the asteroid as bodies rapidly expanded to fill ecological niches. DNA evidence shows South American monkeys and rodents rafted across the Atlantic from Africa on storm vegetation. He discusses the ethics of cloning woolly mammoths, noting it may soon be possible but raises questions about returning ice-age species to a radically altered world humans created. Throughout, Brusatte emphasizes that modern birds are living dinosaurs, the only lineage to survive to the present day.