# Scientists learn why a sensitive part of our DNA is actually a built-in shield against the sun

Source: [Earth.com](https://www.earth.com/science/scientists-learn-why-a-sensitive-part-of-our-dna-is-actually-a-built-in-shield-against-the-sun/) · 2026-11-14 · Earth & Climate
Page: https://themorning.science/story/scientists-learn-why-a-sensitive-part-of-our-dna-is-actually-a-built-in-shield-a-6324f99c6b3e3724
Kind: research · Impact: low

## In brief

- Early Earth had no ozone layer, so early life was exposed to intense ultraviolet light.
- Scientists were puzzled why DNA evolved to use thymine, a building block that takes significantly more UV damage than similar alternatives.
- The Earth.com article reports that researchers have explained why this sensitive DNA component works as a built-in shield against sunlight.

## Why it matters

The finding offers a chemical explanation for why DNA uses thymine, which bears on how early life coped with UV exposure before the ozone layer formed.

## Coverage

- [Scientists learn why a sensitive part of our DNA is actually a built-in shield against the sun](https://www.earth.com/science/scientists-learn-why-a-sensitive-part-of-our-dna-is-actually-a-built-in-shield-against-the-sun/) — Earth.com, 2026-11-14

Tags: dna, thymine, uv radiation, evolution, origin of life

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Brief generated by AI (claude-haiku-5-5) from the reporting listed under Coverage. Headlines belong to their publishers. The Morning Science – https://themorning.science