Paleogenomics and its Importance

This year’s Nobel Prize in Physiology went to Swedish geneticist Svante Pääbo, a pioneer of paleogenomics, or DNA extraction to study ancient humans. This is one of the important topics which are trending in recent times so aspirants need to prepare it thoroughly for upcoming exams like UPSC, SSC, State PSC, and others. This will give an edge to the aspirants over others in getting good marks.

What is the Meaning of Paleogenomics?

• Studying ancient DNA provides an independent method for testing evolutionary theories and population relationships. In 2018, an analysis of DNA extracted from human bones at Rakhigarhi, Haryana (said to be the site of the most important civilization in the Indus Valley) sparked an ancient debate about the old Native Americans. 
  
• Dating to about 4,500 years ago, these fossils have better-preserved DNA and are about 10 times younger than those analyzed in Pääbo’s lab. The Rakhigarhi fossils indicate that these Harappan inhabitants had no Central Asian or Iranian peasant ancestry, prompting debate as to whether this proves or refutes “Aryan migration”. 
  
• Paleogenomics also provides clues to disease, as researchers analyze tooth fossils to gain insight into tooth infections.

What is the Significance of Pääbo’s Work?

• Historically, the study of ancients has been limited to the analysis of bones and surrounding objects, such as weapons, instruments, tools, and dwellings.
  
• Pääbo pioneered the use of his DNA, the genetic blueprint found in all life, to study questions about the relationships of various ancient human species.
  
• He found that Neanderthals, his 100,000-year-old evolved human cousins, interbred with humans and retained some (about 1-4%) of their European and Asian ancestral genes. Proved.  Then, after analyzing a 40,000-year-old finger bone from a Siberian cave, Pääbo’s lab proved it belonged to a new hominin species called the Denisovans.
  
• This is the first time that a new species has been discovered by DNA analysis, and this species also coexisted and interbred with humans.

How can we Extract DNA from Fossils?

• The challenge with extracting DNA from fossils is that DNA degrades fairly quickly and little material is available. Such bones may have passed through multiple hands, making them more likely to be contaminated with DNA from humans and other bacteria. This is one of the major obstacles in analyzing DNA from fossils.
  
• One of Pääbo’s early attempts was to extract DNA from a 2,500-year-old Egyptian mummy. This attracted attention and helped his career, but he said much later that the mummy’s DNA was likely contaminated.
  
• DNA is concentrated in two different compartments in the cell. The nucleus and mitochondria, the latter being the cell’s powerhouse. Nuclear DNA stores most of the genetic information, while the much smaller mitochondrial genome exists in thousands of copies and is therefore more searchable.
  
• Pääbo has used his technique to successfully sequence a region of mitochondrial DNA from a 40,000-year-old bone fragment. This was the first time a genome from an extinct human relative had been assembled.
  
• They then extracted enough nuclear DNA from Neanderthal bones to publish the first Neanderthal genome sequence in 2010. This is important given that the first complete human genome was only published in 2003.

What did Pääbo’s Work Show?

• Pääbo’s most important contribution was to be able to reliably extract and analyze his ancient DNA and study which parts of his DNA clearly distinguish humans or Neanderthals compared to other humans and primates.
  
• A comparative analysis of the human genome shows that the latest common ancestor of Neanderthals and Homo sapiens lived about 800,000 years ago.
  
• In 2008, a 40,000-year-old finger-bone fragment unearthed from a cave in a region of Siberia called Denisova yielded DNA from an entirely new species of hominin called Denisova, according to analysis in Pääbo’s lab. was given. 
  
• This was the first time a new species had been discovered based on DNA analysis. Further analysis showed that they also interbred with humans and that 6% of the human genome in parts of Southeast Asia is of Denisovan ancestry.