Relevance: GS-3 (Science & Technology – Biotechnology) | Source: The Hindu 

1. The Context

A landmark genetic study led by Harvard Medical School has mapped 15,836 ancient human genomes alongside modern DNA sequences.

The study reveals that humans have undergone significant evolutionary changes over just the past 10,000 years. These genetic shifts were driven directly by natural selection as human populations adapted to changing environments, diets, and new diseases.

2. Core Scientific Concepts

• Ancient DNA (aDNA): Genetic material extracted from ancient skeletal remains like bones and teeth. It helps scientists track historical population movements and health trends.
• Radiocarbon Dating (Carbon-14): A scientific method used to find the age of organic remains up to 50,000 years old. It measures the steady breakdown of the radioactive isotope Carbon-14 after an organism dies.
• Natural Selection: A biological mechanism where traits that help a person survive and reproduce become more common in a population over multiple generations.

3. Key Evolutionary Changes Discovered

The study showed how human genes changed rapidly to survive historical pressures:

• Skin Tone Adaptation: Around 8,000 years ago, as humans moved to areas with less sunlight, natural selection favoured lighter skin tones. Lighter skin synthesizes Vitamin D more efficiently, protecting against bone diseases.
• Immunity against Pathogens: A specific mutation (the CCR5 gene variant) that provides modern resistance to HIV-1 increased sharply between 6,000 and 2,000 years ago. Since HIV is a modern virus, this mutation originally evolved to fight an unknown ancient disease.
• Blood Group Shifts: Over the last 6,000 years, the ‘B’ blood type became more common in certain regions, likely as a survival response to changing bacterial and viral exposures.

4. UPSC Value Box: The Indian Genomic Landscape

• Complex Genetic Ancestry: Modern Indian populations carry a mixed genetic history from ancestral indigenous groups (Ancestral South Indians), Iranian Neolithic farmers, and Western Steppe herders.
• Genome India Project: A flagship national project under the Department of Biotechnology (DBT) that successfully sequenced 10,000 whole genomes of healthy Indian citizens to build a reference database for personalized medicine.
• The Rakhigarhi DNA Study: A major ancient DNA study on Harappan skeletons which revealed that the Indus Valley Civilization population was indigenous and did not have genetic inputs from Steppe pastoralists during that specific era.
• The Preservation Challenge: India’s hot and humid tropical climate accelerates the chemical degradation of organic matter, making the extraction of ancient DNA highly challenging.

With reference to biotechnology and genetic research in India, consider the following statements:

1. Ancient DNA (aDNA) is highly stable and preserves better in tropical, humid climates like India compared to colder regions.
2. The Genome India Project is a flagship initiative aimed at sequencing the whole genomes of diverse Indian populations to create a reference database.
3. Radiocarbon dating utilizes the predictable decay of the Carbon-14 isotope to determine the age of organic materials.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Correct Answer: (b) 2 and 3 only

Explanation Hints:

• Statement 1 is incorrect: High heat and humidity cause rapid chemical degradation of organic matter, making ancient DNA extraction in tropical countries like India exceptionally difficult.
• Statement 2 is correct: The Genome India Project successfully sequenced 10,000 genomes to understand the vast genetic diversity of India and aid biomedical research.
• Statement 3 is correct: Carbon-14 dating tracks the steady breakdown of radioactive carbon in dead organisms to estimate their historical age accurately.