Tens of millions of years ago, cephalopods were hiding from their enemies in clouds of ink. And it turns out that cuttlefish today produce ink that’s almost identical.

Researchers found fossils of two giant cephalopods that swam the seas more than 160 million years ago. Each one contained a preserved ink sac. Analysis of the sacs revealed that some melanin pigment—the stuff that makes the ink dark—had survived. Plus, the chemical makeup of the melanin was virtually the same as the pigment found in modern-day cuttlefish ink. The work is in the Proceedings of the National Academy of Sciences. [Keely Glass et al., "Direct chemical evidence for eumelanin pigment from the Jurassic period"]

It’s rare to find preserved soft tissue in the fossil record. In addition, biomolecules often break down, leaving none of the original organic compounds. Melanin, however, has a sturdy structure that resists this fate. And the methods these researchers used to isolate it from the fossils could help other paleontologists better identify preserved organic molecules and their functions.

The finding also demonstrates that when something works, evolution usually leaves it alone. Because if it ain’t broke, don’t fix it.

—Sophie Bushwick

[The above text is a transcript of this podcast.]