How do oxygen atoms in ancient eggshells reveal plant climate reactions?

Oxygen atoms in ancient eggshells act like tiny time machines that tell us about how plants reacted to old climates.

Imagine you're baking a cake and you use sugar from a long time ago. The kind of oxygen in that sugar might be different than the oxygen we have today, just like how the oxygen atoms in ancient eggshells can show us clues about past weather patterns.

When plants grow, they take in carbon dioxide from the air and use it to make their food. The kind of oxygen in that carbon dioxide can leave behind little signs, like invisible fingerprints, inside the shells of eggs laid by animals that ate those plants.

So when scientists look at these eggshells using special tools, they can read those fingerprints, or oxygen clues, and figure out what the weather was like long ago. If it was hotter, the fingerprint might be a bit different than if it was cooler, just like how your favorite cookie tastes differently depending on whether you bake it in a warm oven or a cold one.

It’s like finding a diary written by a plant that tells us about the climate it lived through!