It has long been thought that fossils were a dead medium. There was no real way to obtain any sort of genetic material from them due to the vast time periods involved and so taxonomists and other researchers just had to do their best at fitting ancient creatures into the tree of life however they could.
The Difficulty With Fossils
Comparing and referencing them to fossils before and after offered some insights, but there have been plenty of creatures where only one fossil has ever been found and their morphology is so unlike others in that time period that scientists have been baffled on where they should evolutionarily be placed.
Since DNA so quickly degrades over time, with the oldest even just fragments of DNA ever discovered only being from a creature a million years old, there has been little hope for finding anything for things living in the dinosaur era and beyond. And that does still hold true when it comes to DNA. Heck, even with just fragments, there’s often little that can be gathered. Reconstruction is often out of the question and is one of the reasons why a true resurrection of the mammoth will never be possible.
But researchers in Sweden and Lithuania didn’t decide to just give up. In a collaboration between Lund University, Vilnius University, and the Swedish Museum of Natural History, they decided to see if they could use other molecular and chemical markers from fossils to find out more about them. And they hit paydirt.
The Lifespan of Biomolecules
It has only been through recent efforts by other scientists that we’ve discovered that biomolecules, such as cellulose, collagen, and pigments, are able to survive through what is called “deep time”, lasting in fossilized remains for millions of years. Only up to about 190 million years ago, but that’s plenty. That covers a lot of the dinosaur filled Mesozoic era, including the Jurassic and Cretaceous periods.
However, many of these biomolecules undergo some amount of alteration over that time period, making them unsuitable for analysis and identification. Cellulose especially is a victim of this process. The splitting of its long chained polymers and the breakdown of volatile compounds contributes to this.
Others do not break down so much though. Spores, pollen, and molecules normally found in the waxy cuticle on the outer edge of leaves are more protected from such occurrences. This resilience means molecules found within these parts or produced pieces of the plants have a greater likelihood of having preserved biomolecules.
Hypotheses Confirmed and Disproven
Using these more stable and measurable molecules, the scientists conducted an infrared spectroscopy scan on several fossilized plants which had existing hypotheses on their relationships to living species. They were able to confirm some such hypotheses and disprove others, such as that the Nilssoniales and Bennettitales fossilized groups are related to each other, but not to modern cycad seed plants as was originally expected.
They also found that the Czekanowskia is related to the Ginkgo line, which is an interesting find due to there only being one living species of Ginkgo found today. The final thing they disproved and confirmed was that the Allocladus fossils are also related to Ginkgos and not conifers, as was previously thought.
With this success, the researchers plan to conduct further chemotaxonomic investigations of other fossilized plants and expect other scientists to use their methods on perhaps other forms of life, if stable biomolecules can be identified to focus on. For plants, at least, this research will further our understanding of how ancient species relate to each other and to their modern descendants.
Photo CCs: Ginkgo biloba (2) from Wikimedia Commons