Evolution Isn't Supposed to Go Backwards — This Lizard Proves It Can

What the film says

1. A January 2026 study in the Biological Journal of the Linnean Society analysed 643 living and extinct species to reconstruct 320 million years of reptile skin-bone (osteoderm) evolution.

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2. Most lizards first evolved osteoderms in the Late Jurassic and Early Cretaceous.

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3. The ancestors of monitor lizards lost osteoderms, likely because an active lifestyle worked better without the weight.

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4. Goannas re-evolved osteoderms after reaching Australia about 20 million years ago, in the Miocene, as the climate dried. This challenges Dollo's law.

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5. Osteoderms may have helped goannas reduce water loss in arid landscapes.

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6. Frogs re-evolved lower teeth after losing them more than 200 million years ago, while birds lost their teeth about 116 million years ago.

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7. Proposed exceptions to Dollo's law include stick-insect wings, lower teeth in frogs and a regained coiled shell in slipper snails.

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