A hairdresser with no archaeology training solved a Roman mystery | Sam Kean

Scientific concepts, discoveries, and nature phenomena

1) Roman self-healing concrete (materials science / geochemistry)

• The Romans used a concrete recipe involving quicklime (calcium oxide).
• Archaeologists originally found undigested lumps of quicklime in Roman concrete and assumed it was a mixing error.
• MIT researchers (including a small number of archaeologists) recreated Roman concrete and found:
  • In normal concrete, infiltrating water can freeze, expand, and crack the material.
  • In Roman concrete, infiltrating water reacts with the undigested quicklime, producing a filling substance that fills voids.
• Result: the concrete behaves as self-healing, strengthening over time, contributing to greater durability than typical modern concrete.

2) Roman hairstyling reconstruction via underlying technique (history of technology / materials & methods)

• A Baltimore hairdresser, Janet Stevens, noticed Roman busts and their highly detailed hairstyles—especially the back with massive curls/spirals.
• She first tried to recreate the styles using modern hairstyling tools, but she could not match the results.
• Turning to ancient literature on Roman beauty/hair styling, she found:
  • Earlier writers’ descriptions did not correctly capture hair physics or how to manipulate hair effectively.
• Methodological breakthrough:
  • Because Stevens did not read Latin, she used Google Translate line-by-line.
  • She eventually found a clue about a needle, realizing the hairstyle was not simply sculpted or pinned.
  • She inferred that hair was sewn into place using needle and thread.
• After applying sewing-based construction, she was able to recreate the hairstyles, and later produced research that influenced the study of Roman beauty/hair.

3) Reinterpretation of garum (microbiology/fermentation chemistry applied to ancient cuisine)

• Garum was commonly misinterpreted as “rotten fish sauce”—an odor-based, decomposed product.
• Modern cooks and chefs argue it was instead controlled fermentation:
  • Fish was fermented, breaking down muscle and producing a flavorful sauce.
• Modern analogy: similar in role to Thai fish sauce, which is widely used today.
• Chemical/culinary implications mentioned:
  • Adds umami (savory, protein-like taste).
  • Provides salt, which can “brighten” dishes.
• Cultural point: Romans reportedly used garum broadly, including in desserts—something modern diners might find surprising.

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Researchers / sources featured

• Sam Kean (science writer; narrator)
• Janet Stevens (Baltimore hairdresser; Roman hair styling research)
• MIT (institutional source for the Roman concrete recreation work)
• Google Translate (tool used to translate Latin lines during the hairstyling investigation)