Image of the Day: True Biological Colors of a 47-million Year Old Beetle


This leaf-beetle fossil from the fossil pits in Messel, Germany represents the purest of biological colors retrieved from prehistoric Earth. A study led by Yale University paleogeologist Maria McNamara analyzed 10 beetle fossils, ranging from 15 million to 47 million years old, which owe their enduring shades to the phenomenon of structural coloration, which is produced by the interaction of light with nanometer-scale surface geometries.

“Structural colors don’t need chemicals at all,” said McNamara. “What we wanted to find out was, what kind of structures in the fossils make the color? And are the colors we’re seeing today in the fossils the same as when beetles were alive millions of year ago?”

The Yale team took .00008 millimeter-wide samples of the fossils’ surfaces shape and created models derived from modern beetle shells to calculate how the fossils ought to look. But, according to their calculations, the fossils now appear just slightly more reddish than they ought to. The fossils don’t perfectly replicate the beetle’s original carapaces, and subtly change how light refracts as it passes through shell layers.

“You need to mentally redshift the color. If it’s green, it’s actually a little more on the yellow side. If it’s blue, it’s a little greener,” said McNamara, who next plans to analyze the colors of moth fossils.

“Holding these fossils is amazing,” she said. “But what I really get a kick out of is investigating the details that are preserved on such a tiny scale. It’s one thing to look at a colored fossil beetle, but quite another to realize the level of preservation extends right down to the level of structures that are smaller than a cell.”


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