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A2.1.8—Dating first cells and LUCA

Radiometric dating estimates ages from predictable isotope decay, using carbon-14 for relatively recent organic remains and potassium-40 for much older rocks associated with early life.

Syllabus
First assessment 2025
Objective
A2.1.8
Level
HL

Exam analysis

Chance of appearing2%of analysed past papers
Latest appearanceMay 2014
Most common paperPaper3
Typical marks2–3

Common command terms

  • Outline
  • State
  • Describe

Scoring notes

Common mistake
Using carbon-14 to date rocks or fossils billions of years old.

Recent exam appearances

May 2014Paper3 ["HL"] · TZ22(d)[ 3 ]A2.1.8—Dating first cells and LUCA
May 2014Paper3 ["HL"] · TZ12(a)(ii)[ 2 ]A2.1.8—Dating first cells and LUCA
Practice this objective

Coverage 2014–2014 · Updated 15 Jul 2026

Concept essentials

  • Radioactive isotopes decay at predictable rates expressed by half-life.
  • Carbon-14 dates relatively recent once-living material.
  • Potassium-40 to argon-40 ratios can date much older rocks.
  • The isotope system must be appropriate for the material and expected age.
ConceptIB Biology HL