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Continuously updated · latest Sep 7, 2026

Lessons that are free to use in any classroom, new research, changes to the dataset, and plain-language explainers. Every entry says which subject it belongs to and what you need to know before reading it. Medical information goes stale, so entries are revised when the evidence moves — revised entries show their update date, not just the day they were first published.

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A dark card reading "your calculation will be wrong. that is the lesson." — the cover for a free classroom genetics lesson on lactase persistence.

Lesson: the milk mutation

BiologyGeneticsStatisticsSocial studies Age 13+ Intermediate

A free genetics lesson on natural selection, with no equipment needed. The class computes a prediction from real allele frequencies, gets a clean answer, and then finds out it is wrong — because the same solution evolved four separate times in the last few thousand years.

Updated Sep 7, 2026 22