I remember the experience as if it happened yesterday.
I was with my family for a vacation on the Big Island of Hawaii. We happened upon an out-of-the-way swimming spot that was a natural pool free from waves because of the sand bars. We later learned from locals that sea turtles were attracted to this spot to feed due to the calm waters. As my family enjoyed a swim in the pool, we suddenly found ourselves in the middle of a large group of green sea turtles. We were of no concern to them as they munched algae off the rocks. They fed for well over an hour before swimming back to the open ocean.
We could hardly believe what had happened.
Sea Turtles The sea turtles found in Hawaii are green sea turtles. They are among seven species of sea turtles alive today that include: green, hawksbill, Kemp’s ridley, olive ridley, leatherback, loggerhead, and the flatback, which is found only in Australia.
Sadly, all sea turtle species are endangered. If these animals are lost, not only would their absence result in the loss of beautiful and majestic creatures, but it would also harm ecosystems in the ocean organized around seagrass beds—part of the sea turtle diet.
Life scientists want to understand sea turtles to help them flourish. Part of this understanding involves learning about their natural history. Unfortunately, the fossil record is scant and offers little help.
For this reason, the recent recovery of a fossilized carapace (shell) from the Chagres Formation of Panama by a research team from Colombia has generated excitement.1 This formation dates to the Upper Miocene (11.5 to 5.3 million years ago). The newly discovered specimen is a member of the genus Leipochelys, which includes the Kemp’s ridley and olive ridley species. The carapace displays differences compared to extant members of Leipochelys, and may well represent an ancient species of sea turtle that no longer exists.
Soft Tissue Finds The Chagres Formation has also yielded fossil fish and cetaceans. These fossils are extremely well preserved. For this reason, the researchers decided to examine the carapace fossil for micro-anatomical features such as cells and blood vessels.
Using EDTA (ethylenediaminetetraacetic acid) treatment, the researchers were able to remove the mineral component from a small piece of the fossil carapace.
They could hardly believe what happened next.
They discovered preserved blood vessels, osteocytes, and collagen fibers. Some of the osteocytes have a small oval structure in their interiors that resembles the cell’s nucleus. And some of these oval structures stained when treated with a compound that detects DNA.
Though not a first—the discovery of remnants of osteocytes and blood vessels, along with the possible preservation of DNA fragments, has been reported for only two dinosaur fossils—this find is still exciting. This turtle specimen gives researchers a window into the biodiversity that existed when the Isthmus of Panama formed about 3 million years ago. And it adds to the growing excitement about the potential of fossils to yield soft tissue remnants.
Most paleontologists are thrilled at the prospects of retrieving soft tissue materials from fossil remains. These discoveries add another dimension to their understanding of the biology of Earth’s past life and the natural history of extant organisms.
Soft Tissues in Fossils and Implications for the Age of the Earth Most young-earth creationists (YECs) are also excited about the recovery of soft tissue remnants from fossil remains, but for a different reason. They argue that these discoveries are evidence that the fossil record can only be a few thousand years old—not millions of years. There’s no way that soft tissues and the biomolecules that comprise them could survive that long, they reason. If so, then it means the results of radiometric measurements must be flawed if they return an age date for fossils on the order of tens to hundreds of millions of years. They conclude that the best way to interpret the fossil record is that it’s the result of a global deluge that occurred a few thousand years ago.
On the surface, this argument carries a bit of a punch. How can soft tissue materials survive for millions of years?
Means of Soft Tissue Preservation As an old-earth creationist (OEC) who is persuaded that Earth is 4.5 billion years old and life has been present on Earth for nearly 4 billion years, this provocative question prompted me to write the book Dinosaur Blood and the Age of the Earth. It should be of no surprise that I demonstrate in the book that radiometric dating is reliable. The fossils yielding soft tissues are truly tens to hundreds of million years in age. Thus, there must be some means for soft tissue materials to endure. And there is. Before I describe the general mechanism for survival of these materials, it’s important to understand what’s been recovered from fossil remains.
YECs give the impression that the soft tissue materials are not only original but intact and unaltered. This misrepresentation is unfortunate. Paleontologists have recovered remnants of soft tissue materials that have experienced diagenesis (physical and chemical changes that occur during the conversion of sediment to sedimentary rock) during the fossilization process. The remnants of cells and blood vessels discovered by paleontologists in the turtle carapace have retained their original physical shape, but during diagenesis they’ve been chemically altered—with the breakdown products of the original biomolecules still harbored in the cell-like and blood-vessel-like structures.
YECs rightly argue that biomolecules (and the soft tissues that they form) readily undergo degradation by several distinct mechanisms. But life scientists have discovered several previously unrecognized protective mechanisms. These mechanisms extend the time that the diagenetically altered biomolecules survive. (For details of both types of mechanisms, see Dinosaur Blood and the Age of the Earth and the articles listed in the Resources section.) It’s a competition between degradation and preservation.
These protective mechanisms delay the complete disappearance of the biomolecules that form soft tissue structures long enough for them to be entombed by the mineralization process that occurs during fossilization. This entombment entraps any remaining organic materials. And, once entombed, the breakdown of these materials significantly slows down. In some instances, the degradation process might be altogether arrested.
For this fossil, the race between disappearance and entombment appears to have been won by entombment for the biomolecules and microanatomical structures that made up the soft tissues of the fossil carapace. The researchers foresaw this victory because the carapace, along with other fossils from the Chagres Formation, are so well preserved.
More Soft Tissue Protection from the Shell The mineral components (hydroxyapatite) of the bone that contributes to the turtle’s shell structures offer protection from degradation. The mineral matrix surrounds osteocytes. These cells reside in spaces inside the bone called lacunae. These openings in the bone form when cells become trapped within the bone matrix that they help produce. (It is sort of like the person who paints themselves into a corner.) The blood vessels (which are remarkably durable structures designed to withstand high pressures as the heart pumps blood through them) that permeate the turtle shell bone are also protected by the mineral matrix during fossilization. In addition to hydroxyapatite, bone also contains the protein collagen. Collagen is a highly durable fibrous material. Like osteocytes and blood vessels, these tough protein fibers are protected from breakdown by their interactions with the hydroxyapatite of the matrix.
The bottom line: There are good explanations for how collagen fragments, and the remnants of osteocytes, and blood vessels could endure for 5 to 10 million years in the fossil carapace. And with these explanations, no good reasons remain to think that soft tissue remnants evince a young Earth. It may be hard to believe what happened, but it looks like these majestic creatures were endowed with preservation properties that allow us to appreciate their design.
Edwin-Alberto Cadena, Carlos De Gracia, and Diego A. Combita-Romero, “An Upper Miocene Marine Turtle from Panama that Preserves Osteocytes with Potential DNA,” Journal of Vertebrate Paleontology 23, no.1 (September 28, 2023): e2254356, doi:10.1080/02724634.2023.2254356.
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