Sea Turtles are one of the most fascinating creatures in the world. When snorkeling in the middle of the Caribbean you hope and pray that you get to swim along with one of these wonderful creatures. But little did you know, they have millions of years of history hidden within their shells. Currently, only 7 species of sea turtles are alive, among the seven are those in the genus Lepidochelys: the olive ridley and the Kemp’s ridley. These two species are some of the most popular in the Caribbean Sea yet we know so little about their history. Until…
A group of paleontologists found remains of a turtle shell in 2015 in the Chagres Formation on Panama’s Caribbean coast. This turtle shell happened to be 6 million years old and it represents the oldest known fossil evidence of Lepidochelys turtles.
When analyzing the fossil, the scientists discovered preserved bone cells called osteocytes. These bone cells are the most abundant in the vertebrates and have nucleus-like structures. To test for genetic material the group used DAPI, a blue-fluorescent DNA stain. The test was successful and they were amazed because this was the first time DNA remains have been found in a fossilized turtle that is millions of years old. Not only does this discovery bring understanding to the biodiversity present in Panama millions of years ago, but it also brings a whole new topic of molecular paleontology.
Molecular paleontology is a study of ancient and prehistoric biomatter including proteins, carbohydrates, lipids, and DNA that can sometimes be extracted from fossils. The understanding of how these complex molecules such as DNA and proteins can be preserved in fossils will continue to help scientists now to understand how soft tissues can be preserved over time. In Unit 1 of AP Bio, we are introduced to DNA. DNA is a fascinating molecule that carries most of the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses. It is composed of two long strands forming a double helix structure. Each strand is made up of nucleotides, which consist of three components: Deoxyribose Sugar which makes up the backbone, a Phosphate group that contributes to the backbone structure, and a Nitrogenous base whose sequence encodes genetic information. At this point you may be thinking, why is this turtle so special? Can’t they find DNA in every fossil? Well, you would be shocked; before the discovery of DNA in this 6 million-year-old turtle, scientists were simply amazed by discoveries of DNA over 1 million years old. This is because DNA consists of sequences of base pairs that are chemically linked along the sides of a double-helix structure, resembling a twisting ladder. Being an organic substance, the constituent parts of this helical structure can deteriorate naturally over time. In the absence of active cellular processes within a living organism to repair and replicate DNA, it can degrade relatively quickly, rendering its components meaningless. Although DNA is plentiful and easily obtainable from living organisms, the task of retrieving viable DNA becomes increasingly challenging with extinct organisms, especially the further back in time they lived. All of these reasons indicate why this singular turtle fossil has more to tell about our genetic code than the millions of other fossils we have found over millions of years. Before reading these articles I had never understood how we were able to learn so much about animals and their ways of life just by a single fossil. But this discovery begs the question of why the DNA was able to survive so long within the shell of a turtle and not in the million of other animals around the world?
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