Metal traces help scientists “color in” fossilized animals

Courtesy of the University of Manchester
and World Science staff

Sci­en­tists say they have tak­en a big step in learn­ing the col­ors of the first birds and some oth­er an­cient an­i­mals, us­ing traces of cop­per found in the fos­sils.

A new anal­y­sis in­clud­ed the old­est beaked bird known, the 120 mil­lion year old Con­fu­ciu­sor­nis sanc­tus, and the 110 mil­lion year old Gan­sus yu­me­nen­sis, which looks like the mod­ern grebe and rep­re­sents the old­est ex­am­ple of mod­ern birds.

White shows the dis­tri­bu­tion of cal­ci­um in this bird's neck feath­ers, which in turn is con­trolled by met­al traces of dark pig­ments, re­search­ers say. This would mean the downy feath­ers were orig­i­nal­ly dark in this bird, Con­fuc­ius­or­nis sanc­tus.  (Im­age cre­at­ed by Greg­o­ry Stew­art/SLAC)

“Cop­per can be mapped to re­veal as­ton­ish­ing de­tails about colour in an­i­mals that are over 100 mil­lion years old,” said Uni­vers­ity of Man­ches­ter, U.K. ge­o­chem­ist Roy Wogelius. He is the lead au­thor of a pa­per on the find­ings pub­lished in the June 30 ad­vance on­line edi­tion of the jour­nal Sci­ence.

“Even more amaz­ing is to real­ize that such bi­o­log­i­cal pig­ments,” or mo­le­cules re­spon­si­ble for much bi­o­log­i­cal col­or­ing, “can now be stud­ied through­out the fos­sil record,” he added. That can work “probably back much fur­ther than the 120 mil­lion years we show in this pub­lica­t­ion.”

Wogelius and col­leagues joined sci­en­tists at SLAC Na­tional Ac­cel­er­a­tor Lab­o­r­a­to­ry in the U.S. and used a ma­chine called the Stan­ford Syn­chro­tron Radia­t­ion Light­source to bathe fos­sils in in­tense X-rays. The in­ter­ac­tion of these X-rays with the chem­is­try of each fos­sil let the rec­og­nise the chem­is­try of eu­mel­a­nin, an dark pig­ment, in feath­ers from dino-birds and the eye of a 50-mil­lion-year-old fish.

Eu­mel­a­nin is probably the most im­por­tant pig­ment in the an­i­mal king­dom and gives dark shad­ing to hu­man hair, rep­tile skin, and feath­ers, the re­search­ers said.

The key was iden­ti­fy­ing and im­ag­ing trace met­als in­cor­po­rat­ed by an­cient and liv­ing or­gan­isms in­to their soft tis­sues, in the same way that all liv­ing spe­cies do to­day, in­clud­ing hu­mans. With­out es­sen­tial trace met­als, key bi­o­log­i­cal pro­cesses in life would fail and an­i­mals ei­ther be­come sick or die. Us­ing a new tech­nique called rap­id scan X-ray flu­o­res­cence im­ag­ing, the team tracked down these es­sen­tial trace met­als, which sur­vive even af­ter pig­ment-containing com­part­ments of cells break down.

“The fos­sils we ex­ca­vate have vast po­ten­tial to un­lock many se­crets on the orig­i­nal or­gan­is­m’s life, death and sub­se­quent events im­pact­ing its pre­serva­t­ion be­fore and af­ter buri­al,” said Phil Man­ning, a sen­ior au­thor on the pa­per and Uni­vers­ity of Man­ches­ter pa­lae­on­tol­ogist. “To un­pick the com­pli­cat­ed chem­i­cal ar­chive that fos­sils rep­re­sent re­quires a mul­ti­dis­ci­pli­nary team that can br­ing into fo­cus many ar­eas of sci­ence... we now have a chem­i­cal roadmap to track si­m­i­lar pig­ments in all life.”