Molecular Archaeology-Let’s rewrite the History with ancient DNA

Sayanti Pal, Amity University Kolkata

Until the 1980s most of the researchers used to believe that no detectable genetic material is preserved in archaeological remains due to the rapid decay of bio-organic molecules. The invention of different molecular techniques made possible the detection and characterization of organic compounds present in archaeological remains. Reading the DNA sequence of genetic material preserved in archaeological remains allows us to gain information about the unrevealed mysteries of the ancient world, and their relationship with us. Have you ever thought like, “Are we the descended of Harappan Civilization?” 

The bioarchaeologists have studied the human DNA from Harappan Civilization and suggest that it is largely expected that the modern people in India are descended from this ancient civilization. This finding was reported in the Journal Cell.

Shaping the Story:

The oldest DNA from our Homo genus is a piece of 430,000 year-old genetic code from the Stone Age found in Spain’s  Sima de Los Huesos cave which tells us that the Neanderthal ancestors stayed at a cool 50 degrees Fahrenheit. Ancient DNA (aDNA) extracted from one finger fragment and three teeth found in Siberia revealed Denisovans, an unknown type of extinct human. Ancient DNA (aDNA) analysis of wheat remains was very useful in taxonomic identification and the estimation of the possible bread-making quality of the wheat grown at an Early Bronze Age site in Greece. 

The protein residues found in Mesopotamia ceramic pots were detected using different immunological methods which discloses the fact that dairy farming was well-developed during the Iron Age, around 2,500 years ago. 

Analysis of human DNA from the skeletons tracked diseases such as leprosy which is now confined to relatively few tropical areas in Africa, Asia, and South America. History says, during Medieval Age leprosy was endemic in Europe due to poor sanitation and overcrowding. This confirmed that the disease originated in the old world, from where it spread following human migrations. Sorghum remains to span 1,805 to 450 years old were used along with herbarium and modern specimens to analyze genetic diversity and human selection over time. 

Archaeogenetics:

The development of PCR (Polymerase Chain Reaction) in the late 1980s appears to be the key technique in the field of Molecular Archaeology. Since a minute amount of genetic material can be expected from the extract of the degraded remains, PCR provides a way to make millions to billions of copies of a specific DNA segment that allows the scientists to take a minute amount of sample and amplify it to enough amount to study in details. Different PCR strategies- jumping PCR, multiple primers, nested PCR are used followed by electrophoretic methods to study the desired information. 

Electrophoresis allows detecting the exact measurement of fragment length for kinship analysis as well as direct sequencing of amplified DNA molecules for species identification, Palaeopathology, etc. The field of Ancient DNA (aDNA) studies has been revolutionized with the use of high-throughput Next Generation Sequencing (NGS) techniques that reconstructed the genomes of ancient or extinct organisms. The single-stranded DNA (ssDNA) library preparation method has also gained the interest of many bioarchaeologists. 

The major problem in handling Ancient DNA (aDNA) samples is the high risk of contamination by foreign particles which might provide some non-authentic genetic information to the investigation. Hence, it requires extensive precaution during sample collection, preparation, and DNA isolation. 

Traveling back to the past has always fascinated humans and therefore, the field has captured a huge interest. Ancient DNA (aDNA) analysis promises answers to many questions in Archaeology, such as chronology, migration, domestication, and urbanization leading to new insights in History.

Also read: IVIG:Intravenous Immunoglobulins in the treatment of COVID-19

Source:

1.   Hunter P. Dig this. Biomolecular archaeology provides new insights into past civilizations,     cultures and practices. EMBO Rep. 2007;8(3):215-217. Doi:10.1038/sj.embor.7400923 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1808043/
2.  Pääbo S., Poinar H., Serre D., Jaenicke-Despres V., Hebler J., Rohland N. et al., Genetic analysis from ancient DNAAnnual Review of Genetics, 38(1): 645-79, https://www.annualreviews.org/doi/abs/10.1146/annurev.genet.37.110801.143214
3.  New insights on single- stranded versus double- stranded DNA library preparation for ancient DNA. Wales N., Carøe C., Sandoval-Velasco M., Gamba C., Barnett R., Samaniego J. A. et al., Bio Techniques, 59(6): 368-71, https://www.future-science.com/doi/10.2144/000114364
4. https://www.theatlantic.com/science/archive/2019/09/indus-valley-civilization-dna-has-long-eluded-researchers/597481/

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