Some paleontologists believe they have found fossilized dinosaur DNA. Others are not so sure

Dinosaur researchers working on extremely well-preserved remains of Jehol’s biota in northeast China recently reported that they had detected Biomolecules fossilized in an Early Cretaceous duck-billed dinosaur.

Intriguing microscopic material was found in the femur of a Caudipteryx, a feathered dino resembling a turkey who lived about 125 million to 113 million years ago. The team put the femur cartilage under a microscope and stained it with chemicals called itmatoxyline and eosin, which are used to highlight cell nuclei and cytoplasm in modern cells.

They also stained the cartilage of a chicken and discovered that the dinosaur and chicken cartilage would light up in the same way. Researchers say that nuclei and chromatin, the material our chromosomes are made of, were visible. The team’s research was published last week in the journal Nature Communications Biology.

“Geological data has accumulated over the years and has shown that the preservation of fossils in the Jehol Biota is exceptional due to the fine volcanic ash which buried the carcasses and preserved them down to the cellular level,” said the co-author of the study Li Zhiheng, vertebrate paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, in an academy Press release.

Members of this research team also to describeed find genetic material in another specimen last year; as Gizmodo reported at the time, some scientists were the same skeptical of their claims that traces of genetic material have been preserved in the fossilized skull of Hypacrosaurus. The Caudipteryx fossil in the new work is about 50 million years older than the Hypacrosaur.

“They were identified using completely different methods than the Hypacrosaurus,” wrote Alida Bailleul, lead author of the new document, in an email to Gizmodo. “But what was striking was the hematoxylin staining of the cell nucleus in Caudipteryx – it was comparable to the staining seen in a chicken cell nucleus,” Bailleul said, paleobiologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing.

If this fossil revealed the same structures that have been demonstrated in modern chicken, it would be a remarkable demonstration of how biological material can to preserve and with what mercy the cartilage has been treated by the often destructive processes of the Earth. But not everyone is so convinced of what exactly appeared in the spots.

“I don’t really see how much that has changed here,” said Evan Saitta, a researcher at the Center for Integrative Research at the Field Museum of Natural History in Chicago. “The change in weather that interests us here is not between the hypacrosaur and this new specimen; the difference is the amount of time between DNA preservation well taken care of and any of these fossils.

The oldest sequenced DNA was described in an article this February and came out of teeth of about 1– Million-year-old woolly mammoth. All dinosaurs (except birds) died out 65 million years ago. This makes the materials of the dinosaurs “absurdly older” than the “spectacular” results of the woolly mammoth remains, Saitta said.

So what exactly reacted to the dyes and stains the recent team applied to dinosaur cartilage? Saitta says it could be microbes that have settled in dinosaur remains or mineralization of the space freed by deteriorated genetics Equipment. The latter is the opinion of Nic Rawlence, the director of the paleogenetics laboratory at the University of Otago in New Zealand.

“The current limit of ancient DNA is 1.2 million years ago, and we don’t expect to be able to go much further back in time, certainly not to the age of the dinosaurs, ”Rawlence said in an email to Gizmodo. “While these fossilized cells and DNA from this new dinosaur may look like a modern chicken, they are a stone copy,” where cells and DNA have been replaced with minerals, in the same way that a dinosaur bone is a mineralized version of modern bone.

When bones fossilize, they do so from obvious macroscopic features to the smallest parts of their structure. This allows paleontologists to do things like learn about the growth rate of T. rex, for example, when holes appear in the bone where the blood vessels was. But the genetic material is deteriorating rapidly …an esteemed team that the DNA would cease to be readable after 1.5 million years, causing the mammoth tooth to find itself bustling near the upper limit of the material. And the mammoth remains were that so well preserved thanks to their embedding in permafrost.

“From a chemical point of view, you are dealing here with a completely different configuration of compounds, compared to when you look at permafrost which is roughly comparable to frozen turkey in your freezer to some extent, ”Jasmina Wiemann, molecular paleobiologist at Yale University, said on a video call.

This makes the situation of this million-year-old mammoth fundamentally different from that of the 125-million-year-old Caudipteryx. Although mammoth teeth underwent diagenesis – the process by which organic compounds are gradually replaced by inorganic elements like minerals – they have been cooled by the Siberian climate, preserving biomolecules to this day. (This is also the reason why you sometimes read that Ice Age researchers can eat what they studied, like steppe bison.)

“Regarding actual DNA molecules, I think it is virtually impossible for such molecules to remain in dinosaur material,” wrote Love Dalén, paleogeneticist at the Center for Paleogenetics who was on the mammoth tooth team, in an email to Gizmodo. “We know from both massive empirical studies and theoretical models that even under completely frozen conditions, DNA molecules will not survive more than about 3 million years.”

“Just because different dyes or stains react with parts of a fossilized remnant does not mean that actual DNA molecules remain in the fossil, ”added Dalén.

Moreover, just because a bone fossilizes does not mean that every component of the bone in the pastliving creature is traded tit for tat for any specific mineral or metallic compound. Every dead dinosaur in every a deposit in the world means that a unique set of conditions is met, so that no two fossils are really chemically identical. This means that a Montana Hypacrosaur bone will have undergone a different type of fossilization than that of a Caudipteryx in China, making the job of molecular biologists, geochemists and paleontologists even more complicated.

“It passes, like, a grinder, but what comes out of it ends up being very similar,” Wiemann said. “We lack a fundamental understanding of how fossilization works. I think that’s the whole challenge here.

Mammoth DNA could be sequenced because it was more frozen than fossilized. That is, the DNA has not had the opportunity to interact with the molecular environment around it, and in particular with water, which causes the DNA to break down, such as one of the co-authors of the gigantic article. said Gizmodo.

So besides the question of what exactly was preserved in the Caudipteryx, it is important to recognize that dinosaur DNA cannot be sequenced, to at least not yet. The molecules have just gone through so many changes that they don’t look like the animals they were a part of. But old biomolecules can persist: dinosaur proteins were apparently find on a 200 million year old bone, but as pointed out by a research team including Saitta in a paper, Decomposing dinosaur bones are a happy home for microbes, which can become dinosaur genetic material.

Part of the problem with the recent article, several scientists said, was the staining method used to compare Caudipteryx and chicken nuclei. Hematoxylin and eOsin can bind to all kinds of things, not just genetic material, the researchers said, making the results pretty general. “I think it’s difficult to apply a staining protocol that isn’t at all very specific to something like fossil materials that we don’t even understand what they actually represent,” said Wiemann.

A useful step in resolving such ambiguity would be to cross-stain the staining results with additional independent methods of cartilage examination. Such “triangulation” would help solve the tissue problem, Saitta said. Wiemann suggested using mass spectroscopy to examine the whole bone, and seeing if the material that was stained could be mapped to any nucleic base or to the sugar-phosphate backbone of DNA. This is an “incredibly exciting avenue of research,” added Wiemann, asserting these additional methods would help determine exactly what is preserved in the fossil.

“I firmly believe that if you are going into deep-time biomolecular, you MUST incorporate as many methods as possible, AND you must consider and exclude, with data, any alternatives, such as invasion by microbes, ancient or modern, ”Mary Schweitzer, molecular paleontologist at North Carolina State University and the Museum of the Rockies in Montana, told Gizmodo in an email. Schweitzer co-wrote the article on the hypacrosaur alongside Bailleul, who worked in Schweitzer’s lab. “For me, the ultimate goal is to get sequence information, so anything we can learn about the diagenetic alterations of these recovered molecules becomes critical.”

Two fossils, 50 million years apart, reveal a biomolecular dilemma within two years. If this timeline is to continue, more data could soon arrive, hopefully bringing more clarity to this exciting new area of ​​paleontology.

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