On an ancient ocean floor in the United Kingdom, paleontologists have found prehistoric ink sacs. Belonging to cuttlefish-like animals that lived 160 million years ago, the ink sacs were so exquisitely preserved that scientists were able to analyze their soft tissue. John Simon, a University of Virginia chemist, led a careful analysis of these sacs to determine their contents. Simon and a team of researchers were pleasantly surprised to find that the pigment in the ink was eumelanin, the same pigment found in many organisms today, including bacteria, fungi, squids, birds, and even humans. Eumelanin belongs to a class of pigments known as melanins. Melanins have special chemical properties that allow them to absorb, reflect, and scatter light, creating different wavelengths that result in our eyes seeing different colors. Melanins exist naturally and are responsible for the color in our hair, eyes, and skin. Eumelanin is somewhere in between black and brown in color, and has properties that include protection from the sun and uses in camouflage. The scientists used scanning electron microscopy and mass spectrometry to determine the molecular structure of this familiar pigment in the fossil ink sacs. They managed the tricky process of dissecting the specimen without ruining the molecular structure of the pigment, then compared the pigment with that from modern cuttlefish (Sepia officianalis), which eject it, as do most cephalopods, in defense or when startled (think about Pearl, the little pink octopus “inking” in the movie Finding Nemo). Simon and other researchers discovered that the pigment has not evolved much over time; in fact, 160 million years ago, eumelanin was essentially the same molecule that animals carry today. Not only is this discovery giving scientists insight into the defense mechanisms used by ancient and modern creatures, it also has implications for the study of soft tissue as a means of telling us about prehistoric life forms.
Read more about eumelanin and its ancient past at National Geographic Daily News.
The original study is published in Proceedings of the National Academy of Sciences.
Read more about melanins at WebExhibits.org.