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T-Rex and the World of Dinosaurs

3:41:55 recording · EN · 2 speakers

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Brief overview

T-Rex was a seven-ton, likely nocturnal power-walker that hunted juveniles, not adult Triceratops.

  1. T-Rex hunted juveniles, not adult TriceratopsPredators take prey five to 20% of their mass, and bite-mark and stomach-content evidence points to young animals.
  2. A nocturnal power-walker, not a sprinterGiant eyes, strong smell and efficient locked feet suggest night hunting and running prey down over distance at up to 25 mph.
  3. Fossils erode, so dig them up nowHohn's half-joke: other sciences can wait, but a skeleton on a hillside is gone in six months.
Executive Summary AI
  • Dave Hohn tells Lex Friedman a T-Rex is 12-ish meters long and seven-ish metric tons, an "orca on land" in Tom Holtz's phrase, with tennis-ball-sized eyes, thick bone-crushing teeth and two-fingered arms whose small ligamentous pits suggest they did little.8:27
  • Its movement came from a two-and-a-half to three-meter tail muscle anchored on the femur, and the most detailed speed estimate tops out at 25 miles an hour (40 kph), so it power-walked with a four or five meter stride rather than ran.22:33
  • Drawing on his Microraptor stomach-contents paper, Hohn says predators typically take prey of five to 20% of their mass, so T-Rex targeted juveniles; bite marks on a Mongolian hadrosaur humerus show selective scavenging with the small incisiform front teeth, while healed bites with embedded teeth prove active predation.26:54
  • Around 1,500 to 1,600 valid dinosaur species are named, with 40 to 50 added a year; fossils are found by splitting quarry limestone or walking the right-aged rock, as when a friend spotted five millimeters of claw in northern China that became the 90-plus percent complete Linheraptor.45:41
  • Stan was found in the spring of 1987 in the Hell Creek Formation near Buffalo, South Dakota, dug up by the Black Hills Institute and sold in 2020 for $31.8 million to Abu Dhabi's Department of Culture and Tourism; given $10 billion, Hohn would build a museum and buy fossil-bearing quarries, and he argues fossils must be dug now because erosion destroys them.58:15
Key Quote
“So a colleague of mine, Tom Holtz, described them as an orca on land.”
— Dave Hohn8:51
Key Quote
“The vast majority of active predation is on stuff much, much, much smaller than you.”
— Dave Hohn26:37
Key Quote
“It's really hard to hide a T-Rex.”
— Dave Hohn41:41