Ologies with Alie Ward
Episode: Paleohistology (WHY TEETH EXIST) with Dr. Yara Haridy
Date: January 21, 2026
Guest: Dr. Yara Haridy – Paleohistologist, Evolutionary Biologist, and Science Communicator
Episode Overview
This episode of Ologies delves into the weird and fascinating evolutionary history, structure, and function of teeth through the lens of paleohistology—the study of ancient tissues. Host Alie Ward is joined by Dr. Yara Haridy, a globally recognized paleontologist and science communicator, to explore why teeth exist, how they evolved, and why your teeth are sensitive—blame your fishy ancestors. The conversation ranges from the oldest known “tooth-like” structures, the mysteries they contain about our past, methods used in research, and memorable stories from behind-the-scenes at the Field Museum.
Key Discussion Points & Insights
1. What is Paleohistology?
• Dr. Haridy’s “ology” is paleohistology: the study of ancient tissues.
• Histology = study of tissues; Paleo- = ancient.
• Teeth are composite structures made up of different tissues—enamel, dentine, pulp.
Quote:
“So, like, dentine, enamel…those are words that people have heard from your toothpaste commercials. So those will be the tissues, but the structure as a whole is the tooth.”
— Dr. Yara Haridy [06:25]
2. Path to Paleontology
• Dr. Haridy didn’t grow up a “dino kid”; grew up in Egypt, where paleontology wasn’t a common path.
• Discovered her love for anatomy in pre-med, pivoted through volunteering in a paleo lab in Canada.
• Realized the thrill of discovering prehistoric tissue under a microscope.
Quote:
“You can see cell spaces, you can see lines where like, you know, this animal had a hard winter. All that was recorded in the fossils. And at that point I was like, oh wait, this might be a real...science.”
— Dr. Yara Haridy [09:00]
3. How Did Teeth Evolve?
• Teeth likely originated as odontodes: tooth-like structures on the outside of fishes.
• Odontodes are made of the same materials (enamel, dentin, pulp cavity) but are external.
• Earliest dental tissues appear ~455 million years ago (middle Ordovician).
• These structures served different hypothesized functions:
- Protection (body armor—for defense against sea scorpions, ancient cephalopods, etc.)
- Hydrodynamics (e.g. shark “skin teeth”)
- Sensation
Quote:
“The very first tooth-like structures to appear in the fossil record don’t appear in the mouth. They appear on the outside of fish.”
— Dr. Yara Haridy [13:37]
4. From Odontodes to True Teeth
• The movement from external odontodes to internal ones (i.e., teeth in jaws) occurred in the Devonian period (420–360 million years ago).
• Two main hypotheses:
- Physical migration of tissue/jaw evolution.
- Genetic re-expression (the “tooth” genetic toolkit moved inside the mouth).
Memorable Moment:
Alie likens this to a rogue hair popping up on your chin unexpectedly:
“Kind of like when you get a weird hair that pops up somewhere else, you go, what are you doing here?”
— Alie Ward [21:40]
5. What Counts as a Tooth? Baleen, Beaks, and Radulas
• Patron questions clarified differences:
- Baleen (whales): entirely keratinized, not true teeth or odontodes.
- Bird beaks: keratin; birds’ ancestors had teeth, but modern beaks replaced them.
- Radulas (snails): keratinized feeding structure, not true teeth. • True teeth and odontodes are a vertebrate-only innovation.
Quote:
“Baleen is not teeth. It is completely different tissue… So if they're keratinized, they don't have dentine, they don't have enamel.”
— Dr. Yara Haridy [40:10]
6. Why Are Teeth Sensitive? And Why Do Mammals Only Get Two Sets?
• Sensitivity is a deep evolutionary inheritance—original odontode function may have involved sensation, not just protection.
• Most vertebrates continuously replace teeth (sharks lose a tooth a week!); mammals evolved “precise occlusion,” limiting them to two sets for chewing efficiency.
Quote:
“Tooth replacement or constant tooth replacement is the original state. … Everything kept replacing its teeth until mammals.”
— Dr. Yara Haridy [52:25]
Memorable Moment:
Alie and Dr. Haridy react to the horror of baby X-rays:
“Those look like gravel… Those look like decomposed granite in a fancy garden.”
— Alie Ward [27:58-28:00]
“Terrifying.”
— Dr. Yara Haridy, on “teeth in the wings” X-rays [52:15]
7. How Modern Research Is Done
• Techniques include dental tools, dental putty, high-definition microscopy, and particle accelerators (synchrotrons) for 3D imaging of fossil tissues. • Dr. Haridy’s landmark 2025 Nature paper revealed that previously identified vertebrate “teeth” (Anatolepsis) were actually arthropod sensory structures, not vertebrate! This resets the fossil record for earliest teeth.
Quote:
"Now I use a particle accelerator to image fossils."
— Dr. Yara Haridy [68:35]
8. What Can Fossil Teeth Tell Us?
• Teeth not only reveal diet by shape but also isotopic composition—allowing reconstruction of ancient environments, diets, and migration. • The pulp cavities and nerves of odontodes and teeth are clues to function.
9. Notable Fun Facts & Tangents
• Sharks, catfish, and even ancient fish were/are covered in sensory “teeth.” • Many animals use their teeth/tusks for sensation (elephants, narwhals). • Rodent enamel is yellow due to iron—it's not just dirt! • Beavers, deer, and other animals have evolved highly specialized teeth for their diets. • Modern funding for paleontology is comically low—a single expedition can cost less than a nice dinner in DC.
Notable Quotes & Memorable Moments
On the Beauty of Discovery
“I want everyone to experience the feeling of finding their first fossil because… It’s so weird to just crack open a piece of rock and be the very first person to look at this bone since it was buried 480 million years ago.”
— Dr. Yara Haridy [82:16]
On the Challenges of Science
“The hardest part about my job is that I have to keep thinking about ancient fish while the world is doing what the world is doing… I think about old bones today, even though bombings are happening or economic crashes are happening…”
— Dr. Yara Haridy [80:00]
On Odontodes as Proto-Teeth
“The very first tooth-like structures to appear in the fossil record don’t appear in the mouth. They appear on the outside of fish.”
— Dr. Yara Haridy [13:37]
On the Misidentification in Fossil Record
“Found out that this late Cambrian guy was not a vertebrate at all, but an arthropod.”
— Dr. Yara Haridy [71:28]
On Modern Relevance
“Maybe [sensitive teeth] is an inherited complexity from their original function.”
— Dr. Yara Haridy [78:55]
On Science Communication
"Most people haven't met a scientist. I sure didn’t until I was about to become one. ...The real solution to this is more people interacting with science."
— Dr. Yara Haridy [81:00]
Timestamps for Key Segments
- Paleohistology Defined: [06:02]
- Origins of Dr. Haridy’s Interest: [06:44–09:41]
- Earliest Teeth & Odontodes: [12:02–16:36]
- External vs. Internal Teeth Evolution: [19:40–21:40]
- Tusks, Dentine, and Enamel: [21:53–22:52]
- Teeth Sensitivity Origins: [23:43–24:34]
- The Fossil Fragment Reality: [27:06–29:45]
- Methods & Fieldwork: [32:24–34:36]
- Patron Q&A—Baleen, Beaks, Radulas: [39:10–56:24]
- Replacing Teeth—Why Mammals Are Weird: [51:45–55:14]
- Rodent & Herbivore Teeth: [59:29–60:44]
- Overcrowding in Teeth & Diet Shifts: [62:25–63:48]
- Fossil Teeth Tell All: Isotopes & Diet: [64:33–66:49]
- Landmark Nature Paper & Sensory Origins: [67:35–78:57]
- On Scientific Joy & Philosophy: [82:16–84:10]
Takeaways for Listeners
- Teeth are marvels of evolution—originating as external body armor and only later migrating into mouths.
- Much of what we know comes from cutting-edge lab work and field expeditions that cost less than a used Camry.
- Many “tooth-like” structures in animals (baleen, bird beaks, radulas) are actually not teeth, but keratin-based—a distinction only clear through work like Dr. Haridy’s.
- The sensitivity of our teeth is a vestige of their ancient function, possibly for sensation as much as defense or mastication.
- Modern science often means overturning older “truths” (the earliest “teeth” were actually mistaken identity!).
- There’s still a huge amount not known—especially about the transition from squishy invertebrate ancestors to armored, toothy vertebrates.
- Science is underfunded, and anyone can get involved—whether in the field, lab, or through community science.
- If you find a fossil (especially a tooth), context is as important as the object—call a paleontologist!
The Episode’s Tone
The conversation sparkles with curiosity, humor, and genuine wonder. Dr. Yara Haridy and Alie Ward keep things engaging, relatable, and richly detailed, never shying from geek-outs or hilarious analogies (“like a tiny cottage cheese ceiling” [18:39], “cigarette butts” for shark teeth [51:45], “squishy boys” for early chordates [31:00]). Listeners leave with a deeper understanding of teeth—and a permission slip to nerd out about fossils and the natural wonders lurking behind their own smiles.
Further Resources
- Follow Dr. Yara Haridy: yaraharidy.com | Instagram: @yaraharidy
- Field Museum, Chicago: fieldmuseum.org
- Charity highlighted: The Samir Project (for Gaza humanitarian aid)
- Related Ologies episodes: Garology, Osteology, Urban Rodentology, Beavertology, etc.
Remember to floss—your teeth have survived millions of years for a reason. And if you find a tooth in a rock, give a scientist a call.