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Paleontologists Are Skeptical About Baby Dinosaur Cells Supposedly Found in Fossil – Gizmodo, Gizmodo.com

Paleontologists Are Skeptical About Baby Dinosaur Cells Supposedly Found in Fossil – Gizmodo, Gizmodo.com
[the authors]

[the authors] [the authors]

Artist’s reconstruction of the nesting ground of Hypacrosaurus stebingeri. A deceased Hypacrosaurus nestling can be seen with the back of its skull embedded in shallow waters. The mother is portrayed at right.

Illustration: Michael Rothman

[the authors] With With our deepest regrets to the Jurassic Park franchise, DNA does not preserve well, and no genetic data has ever been recovered for dinosaurs. Recent news suggesting that scientists have found dinosaur DNA certainly sounds exciting, but it’s an extraordinary claim that warrants skepticism. Fossils of baby duck-billed dinosaurs ( Hypacrosaurus stebingeri

) have yielded traces of proteins, chromosomes, and chemical markers of DNA, according to new

research published in National Science Review.

put out by the Science China Press — the scientists, led by Alida Bailleul from the Chinese Academy of Science in Beijing, China, have not actually found dinosaur DNA, but rather materials that are chemically consistent with the presence of DNA . It’s kind of coded language, but it’s an important distinction, and, quite unfortunately, some media outlets have perhaps read too much into the press release.

At the same time, a literal interpretation of the new paper, co-authored by paleontologist Mary Schweitzer from North Carolina State University, is also being frowned upon, as the experts we spoke to said the newly presented evidence is insufficient, inaccurate, and unconvincing.

Uncovering traces or signatures of dino cellular material , chromosomes, amino acids, and DNA would be a monumental and unprecedented achievement. Protein and DNA do not preserve well. To date, the oldest full genome

(in in the fossil record comes from a 1093, – year-old horse found in Yukon permafrost, and the oldest protei ns

from 3.8-million-year-old ostrich egg shells. Finding proteins and DNA from dinosaurs that lived tens of millions of years ago, therefore, would represent a monumental shift in our understanding of how well these microscopic structures can be preserved. These organic materials … are understood to be among the least stable biomolecules over long periods of time and under the heat of deep burial during fossilization, ”wrote Evan Saitta, a researcher from the Integrative Research Center at the Field Museum of Natural History in Chicago, in an email to Gizmodo . “However, it is the extreme age of the samples that is striking. This 206 – million-year-old fossil is, at least, one or two orders of magnitude older than the expected preservation limits of DNA and proteins, ”said Saitta, who was not involved with the new research.

for the new study, Bailleul, Schweitzer , and their colleagues studied fossils of duck-billed dinosaur nestlings found in northern Montana back in the s. The fossilized bones were found buried within the Two Medicine Formation, which dates back to the Upper Cretaceous. Analysis of skull fragments yielded traces of well-preserved cells within calcified cartilage, according to the research, which were compared to similar features in modern emus. viewed through a microscope, a pair of presumed cartilage cells were seen linked together via an intercellular bridge in a manner consistent with cellular division. A dark blob reminiscent of a cell nucleus was also identified, along with elongated structures presumed to be “morphologically consistent” with chromosomes, according to the new paper.

“I couldn’t believe it, my heart almost stopped beating,” said Bailleul in the press release. [the authors] To see if the original molecules were also preserved, the researchers performed immunological and histochemical analyzes of another fossil, also of a nestling Hypacrosaurus found at the same site. When exposed to antibodies of collagen II (the main component of cartilage), the fossilized cartilaginous matrix appeared to react, hinting at the presence of the dinosaur’s original cartilaginous proteins.

Another test was done, in which individual cartilage cells were isolated and exposed to two DNA stains: DAPI (4 ′, 6-diamidino-2-phenylindole) and PI (propidium iodide). DAPI and PI can bind to DNA fragments, and in this case, they performed this binding in a manner seen in modern cells, suggesting this dinosaur’s “nuclear material survived fossilization,” according to the paper. [the authors]

[the authors] [the authors] [the authors]
Isolated chondrocytes of Hypacrosaurus and their positive response to two DNA assays.
Image: AM Bailleul et al.,
We presented multiple lines of evidence. to suggest that remnants of original cells and tissues remain in regions of the skull of this baby dinosaur, ”Schweitzer wrote in an email to Gizmodo. “One line of evidence is that when we stain these cell-like structures with certain stains, they light up in the same pattern as modern cells containing DNA. So, we can say that we have evidence for the presence of material that is chemically consistent with DNA inside these chondrocyte-like structures. ”

something similar in for bone-forming cells (osteocytes), but this is the first such molecular response shown in fossilized cartilage.

“We do not say that it is dinosaur DNA, although that would be a reasonable interpretation, ”Schweitzer said. “We can only determine that through sequence data,” which isn’t possible due to the limitations of the source material.

Writing in the paper, the authors acknowledged the possibility that the samples were contaminated, but they said this was a “plausible explanation in this case” because “the possible preservation of original proteins and DNA in deep time has not been convincingly eliminated with data,” they wrote. In other words, the authors are confident that the dino’s original material is still locked inside the fossil.

The “identification of chemical markers of DNA. in Hypacrosaurus

suggest it may preserve much longer than originally proposed, ”connected the authors in the study. Artist’s reconstruction of the nesting ground of Hypacrosaurus stebingeri. A deceased Hypacrosaurus nestling can be seen with the back of its skull embedded in shallow waters. The mother is portrayed at right.

This is not the first time that Schweitzer has claimed to have uncovered fossilized traces of soft tissue. In addition to the aforementioned (study, Schweitzer has presented evidence of

collagen in T. rex fossils and protein fragments in h adrosaurs , among other research papers.

when asked if he agreed with the interpretations presented in the new paper, Saitta said “no,” and that this paper “presents the most extreme claims to date from some of these authors.” In his email to Gizmodo, Saitta presented a long list of complaints, saying claims of more recent stable proteins (compared to DNA) have been challenged for a variety of reasons, including statistical shortcomings and [the authors] lab contamination

in which he’s listed as first author.

In addition, Saitta said much doubt has been cast on histochemical and immunological staining as a technique to target specific molecules, saying these stains are notorious for producing false positives. He also worries that “many of these supposedly miraculously preserved organic materials” are “misidentified under microscopy,” saying we humans “have a tendency to see patterns in non-patterned data.”

Paleontologist Jakob Vinther from the School of Earth Sciences at the University of Bristol said a “parallel dimension” Currently exists within the discipline in terms of how scientists are interpreting fossils and soft tissues.

“Schweitzer and a few others believe that proteins preserve readily, while archaeologists that are looking at material that are orders of magnitude younger cannot substantiate such claims of wholly intact proteins other than degraded fragments, ”Vinther told Gizmodo. “Archaeologists use other methods, such as mass spectroscopy to investigate degraded proteins, which has led to some tremendous and amazing discoveries. However, every time people try and look at dinosaurs to sequence proteins, they find nothing but contamination. If [the authors] really have intact proteins, mass spectroscopy should easily enable us to confirm these radical claims. ”

Schweitzer, who is

, said skeptics “can say what they want,” but they need to come up with other explanations that fit the data better.

As far as I know, DAPI. and PI do not bind to any other molecule except DNA, ”Schweitzer told Gizmodo. “What else is DNA-like enough to bind these two markers and be localized inside a cell-like structure if it isn’t DNA? Still without sequence data, we can only say it is consistent with DNA. The fact that antibodies raised against collagen II bind this cartilage tissue, but do not bind adjacent bone is also pretty hard to explain unless it is cartilage, especially when all our controls are considered. ”

The debate rages on, as does the search for more evidence. Sadly (or perhaps encouragingly), we’ll probably never be able to reconstruct a whole dinosaur genome and potentially bring an extinct dinosaur back to life, despite what science fiction tells us.

“If the (Jurassic World) movies had more closely adhered to the science, perhaps they would not be so awful to watch, ”Saitta told Gizmodo. “Similarly, as scientists, we cannot get to a point in the future where our research papers are motivated by Hollywood.” [the authors] Read More

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