It’s the first time researchers have been able to detect the chemical signature of red pigment in an ancient fossil, according to a study published Tuesday in Nature Communications. Color is part of how animals have adapted to survive and has played a key part in evolution over millions of years.
The researchers didn’t know what they would find when they studied the mouse fossil, but the surprise was worth their efforts.
“What we found is that the mouse is preserved in absolutely stunning detail, nearly all of the skeleton and most of the soft tissue of the body, head, feet, and tail can easily be recognized,” Uwe Bergmann, study co-author and distinguished staff scientist at the SLAC National Accelerator Laboratory, wrote in an email. “The X-ray maps show that not only are structures preserved, but original biochemical information is resolvable. That was a wonderful surprise.”
But determining color pigments in species that have long been extinct isn’t easy, especially with certain colors.
Ten years ago, the team of researchers was able to isolate the chemical signature of black pigment, like the kind in crow feathers. And now, they have found red pigment, like the color of fox fur. Red pigment becomes less stable over time and is incredibly difficult to detect.
“In mammals and other animals there are two types of melanin, the brownish black eumelanin and the reddish pheomelanin,” Bergmann said. “The importance is not so much the fact that this mouse had this reddish pigment, but the fact that we could identify it in a three million year old fossil. This has implications that there is hope of identifying pigments in many other fossils.”
Intense X-ray tools, like the SLAC’s Stanford Synchrotron Radiation Lightsource and the Diamond Light Source in the UK, provided the brightest sources of light possible to study the fossil.
“The biggest impact to me is the fact that we have now X-ray tools that can recover information about a fossilized organism from tiny traces preserved for millions of years,” Bergmann said. “This was not easy and required a team of scientists with different expertise, including paleontology, geochemistry, and of course X-ray spectroscopy and imaging, which is my field. Being part of such a diverse and interesting team is incredible.”
The X-rays were able to detect trace metals in the pigments themselves, revealing the red color in the mouse’s fur. The metal traces bonded to organic pigments in the tissue, and the researchers compared this with how metals are incorporated in living species. They even translated the findings into sound waves to show that different frequencies are associated with different sounds.
“We understand now what to look for in the future and our hope is that these results will mean that we can become more confident in reconstructing extinct animals and thereby add another dimension to the study of evolution,” said Roy Wogelius, study co-author and geochemist at the University of Manchester, in a statement.
This technique could be applied to other well-preserved fossils to unlock their secrets and reveal some of the mysteries of evolution that are missed when species go extinct. It may even reveal how our climate has changed.
“The fossils we have studied have the vast potential to unlock many secrets of the original organism,” said Phil Manning, lead study author and palaeontologist at the University of Manchester. “We can reconstruct key facets from life, death and the subsequent events impacting preservation before and after burial. Where once we saw simply minerals, now we gently unpick the ‘biochemical ghosts’ of long extinct species.”