Short Wave Episode Summary

Podcast: Short Wave (NPR)
Episode: What Crocodile Bones Teach Us About Dinosaurs
Date: March 9, 2026
Hosts: Regina Barber & Ari Daniel
Featured Guests:

• Dr. Anusia Chinsami-Turan (Paleobiologist, University of Cape Town)
• Quentin Cronier (Head Animal Handler)
• Andrea Plass (Technical Officer, University of Cape Town)
• Maria Eugenia Perera (Biologist)
• Alzette Monkey (Manager, Le Bonheur Reptiles and Adventures)
• Dr. Holly Woodward (Paleo-histologist, Oklahoma State University)
• Dr. Kristy Curry Rogers (Dinosaur Paleobiologist, Macalester College)

Episode Overview

This episode explores how studying the bones of modern crocodiles in South Africa is shaking up our understanding of dinosaur aging. Previously, paleontologists estimated how old dinosaurs were when they died by counting growth rings in their fossilized bones, much like rings in a tree. New research using living crocodiles as proxies suggests those age estimates could be off, challenging assumptions about dinosaur growth and lifespan.

Key Discussion Points & Insights

1. How Scientists Traditionally Estimate Dinosaur Age

• Conventional method:
  • Count growth rings in fossilized dinosaur bones; each ring was believed to correspond to one year (01:03-01:25).
• Dr. Anusia Chinsami-Turan explains:

  "We always thought that these rings are formed annually, meaning, like a tree. You might imagine one ring per year." (01:17)

2. The Fieldwork: Crocodile Relatives as Proxies

• Why crocodiles?
  • Birds and crocodiles are the closest living relatives to dinosaurs (02:07-02:18).
• Research location:
  • Le Bonheur Reptiles and Adventures, just outside Cape Town, houses a large population of Nile crocodiles (03:40-04:05).
• Alzette Monkey (on crocodiles):

  "They're basically the kings of the water bodies in Africa. I mean, they are the custodians of the African rivers." (03:56)

3. Experimental Approach: Marking Bone Growth

• Method:
  • Anusia and her team injected young crocodiles with antibiotics over several months. The antibiotics left a time-stamped marker in the developing bones (05:07-05:23).
• Purpose:
  • This allowed the team to compare the number of visible growth rings to the actual age and growth events of the animals (05:29).

4. Findings: Growth Rings Aren't Annual

• Key discovery:
  • Many young crocodiles had more bone growth rings than their age in years; some two-year-old crocs showed up to five growth marks (07:45-08:02).
  • Notable quote:

    "This is a two year old crocodile. And in many cases, we found up to 5 growth marks in the bones. So there were extra growth marks formed during their short life."
    — Dr. Anusia Chinsami-Turan (07:51)

• Implication:
  • If dinosaur bones grew in a similar fashion, prior age estimates could be inflated; dinosaurs may have been younger than previously thought when they died (08:13-08:31).

5. Expert Reactions and the Scientific Debate

• Dr. Holly Woodward (Oklahoma State):

  "Studies like this one are really important in adding to that body of knowledge of how often growth rings can be reliable. We haven't really done as much ground truthing as we could with modern animals." (09:03-09:15)

  • Points out that some modern animals do have annual rings, and others do not. The exact mechanisms aren't known yet, and growth rings are still a useful starting tool (09:22-09:46).
• Dr. Kristy Curry Rogers (Macalester College):

  "It's sort of a cautionary tale not to over interpret what we can see and know based on bone tissue under the microscope. This confirmed a suspicion that I've often had in my own work, because we still don't understand everything we need to about living vertebrates and how their bones respond to the environments around them." (09:54-10:14)

• Dr. Anusia Chinsami-Turan reflects:

  "We can still get a rough estimate. But people have to realize that it's an estimation." (10:22)

6. Memorable Moments & Humorous Asides

• Regina’s reaction to the croc-filled pools:

  "It sounds awful." (03:53)
  "So scary." (03:55)

• Crocodile handling stories:
  • Andrea Plass admits the largest crocodile “was definitely a bully, and he tried to bully me, and he won. So I had to bring in help.” (06:10-06:18)
• Anusia on the bones’ final secrets:

  "It's all in the bones." (10:44)

7. Listener Question: Do Human Bones Have Growth Rings?

• Bonus Q&A:
  • Humans do have growth rings, but they aren’t usually visible in adults because bones remodel with age and erase the old signals (11:29-11:55).
• Brief clarification by Ari Daniel:

  "Humans do have growth rings. They're just not reported that often because we usually stop growing in our 20s or so...our bones remodel and destroy the presence of previously formed rings." (11:29)

Timestamps for Key Segments

• [00:16-01:47] — Introduction & Traditional Method of Dinosaur Aging
• [02:07-04:05] — Why Study Crocodiles? Tour at Le Bonheur Reptile Center
• [05:07-06:29] — Marking Bone Growth with Antibiotics, Crocodile Growth Stories
• [07:45-08:31] — Discovering Extra Growth Rings
• [09:03-10:14] — Expert Analysis and Debate
• [10:22-10:46] — Reassessing Dinosaur Age Estimates
• [11:29-11:55] — Do Humans Have Bone Rings?

Overall Takeaways

• Growth rings in bones can be misleading in both crocodiles and possibly dinosaurs; more than one ring can appear in a single year, depending on metabolic or environmental factors.
• Dinosaur age estimates and growth rates based on ring counting may need to be reevaluated, but “it’s an estimation” (10:22).
• This research highlights the complexity and unpredictability of bone biology, reminding us that paleontology often relies on tentative inferences rather than hard certainties.

Notable Quotes

• “It's like walking among dinosaurs every day. I'm quite tickled by it, I must say.”
  — Alzette Monkey (04:46)
• “It's all in the bones.”
  — Dr. Anusia Chinsami-Turan (10:44)
• "It's sort of a cautionary tale not to over interpret what we can see and know based on bone tissue under the microscope."
  — Dr. Kristy Curry Rogers (09:54)

In summary, the episode invites listeners into the thrilling detective work of paleobiology and the ever-evolving puzzle of dinosaur lives, revealing that even our oldest questions can have new, surprising answers—sometimes from the bones of living creatures around us.