Molecular paleontology
Molecular paleontology refers to the recovery and analysis of DNA, proteins, carbohydrates, or lipids, and their diagenetic products from ancient human, animal, and plant remains.
In shallow time, advancements in the field of molecular paleontology have allowed scientists to pursue evolutionary questions on a genetic level rather than relying on phenotypic variation alone.
[3] Using various biotechnological techniques such as DNA isolation, amplification, and sequencing[4] scientists have been able to acquire and expand insights into the divergence and evolutionary history of countless recently extinct organisms.
[5][6] In deep time, compositional heterogeneities in carbonaceous remains of a diversity of animals, ranging in age from the Neoproterozoic to the Recent, have been linked to biological signatures encoded in modern biomolecules via a cascade of oxidative fossilization reactions.
[7][8][9][10] The macromolecular composition of carbonaceous fossils, some Tonian in age,[11] preserve biological signatures reflecting original biomineralization, tissue types, metabolism, and relationship affinities (phylogeny).
[9] The study of molecular paleontology is said to have begun with the discovery by Abelson of 360 million year old amino acids preserved in fossil shells.
Produced idea of comparing fossil amino acid sequences with existing organism so that molecular evolution could be studied.
[19] 2010: A new species of early hominid, the Denisovans, discovered from mitochondrial and nuclear genomes recovered from bone found in a cave in Siberia.
[21] 2013: A 400,000-year-old specimen with remnant mitochondrial DNA sequenced and is found to be a common ancestor to Neanderthals and Denisovans, Homo heidelbergensis.
[22] 2013: Mary Schweitzer and colleagues propose the first chemical mechanism explaining the potential preservation of vertebrate cells and soft tissues into the fossil record.
The mechanism proposes that free oxygen radicals, potentially produced by redox-active iron, induce biomolecule crosslinking.
[25][26] 2018: Molecular paleobiologists link polymers of N-, O-, S-heterocycle composition (AGEs/ALEs, as referred to in the cited publication, Wiemann et al. 2018) in carbonaceous fossil remains mechanistically to structural biomolecules in original tissues.
Through oxidative crosslinking, a process similar to the Maillard reaction, nucleophilic amino acid residues condense with Reactive Carbonyl Species derived from lipids and sugars.
[8] 2019: An independent laboratory of Molecular Paleontologists confirms the transformation of biomolecules through Advanced Glycosylation and Lipoxidation during fossilization.
2020: Wiemann and colleagues identify biological signatures reflecting original biomineralization, tissue types, metabolism, and relationship affinity (phylogeny) in preserved compositional heterogeneities of a diversity of carbonaceous animal fossils.
[9] This is the first large-scale analysis of fossils ranging in age from the Neoproterozoic to the Recent, and the first published record of biological signals found in complex organic matter.
The combined hypotheses, along with thermal maturation and carbonization, form a loose framework for biological cell and tissue fossilization.
[28] The Denisovans of Eurasia, a hominid species related to Neanderthals and humans, was discovered as a direct result of DNA sequencing of a 41,000-year-old specimen recovered in 2008.
Analysis of the mitochondrial DNA from a retrieved finger bone showed the specimen to be genetically distinct from both humans and Neanderthals.
From this analysis, they concluded, in spite of the apparent divergence of their mitochondrial sequence, the Denisova population along with Neanderthal shared a common branch from the lineage leading to modern African humans.
[22] Molecular paleontology techniques applied to fossils have contributed to the discovery and characterization of several new species, including the Denisovans and Homo heidelbergensis.
Some examples include the dodo, the great auk, the Tasmanian tiger, the Chinese river dolphin, and the passenger pigeon.
Critics of bringing extinct species back to life contend that it would divert limited money and resources from protecting the world's current biodiversity problems.
As the editors of a Scientific American article on de-extinction pose: Should we bring back the woolly mammoth only to let elephants become extinct in the meantime?
These techniques could also be used to reintroduce genetic diversity in a threatened species, or even introduce new genes and traits to allow the animals to compete better in a changing environment.
[40] When a new potential specimen is found, scientists normally first analyze for cell and tissue preservation using histological techniques, and test the conditions for the survivability of DNA.
[46] On the other hand, DNA extraction from insects can be done by grinding the sample, mixing it with buffer, and undergoing purification through glass fiber columns.
Nuclear DNA normally degrades rapidly after death by endogenous hydrolytic processes,[42] by UV radiation,[1] and other environmental stressors.
