Human Evolution in the Last 10,000 Years

Syllabus: GS3/ Science and Technology

Context

• A major study led by scientists analysed ancient and modern human genomes to understand how humans evolved during the last 10,000 years.

What is Ancient DNA?

• Ancient DNA refers to genetic material extracted from skeletal remains, teeth, and bones of humans who lived thousands of years ago.
• Scientists sequence this DNA and compare it with modern genomes to understand human migration, evolutionary adaptations, disease susceptibility and changes in physical and behavioural traits.

Carbon Dating

• Scientists use Carbon-14 dating to determine the age of ancient skeletal remains.
• Carbon-14 is a radioactive isotope formed by interaction between cosmic rays and atmospheric nitrogen.
• The amount of Carbon-14 decreases after death because radioactive decay converts it back into nitrogen. It has a half-life of 5,730 years.
• Scientists use mass spectrometers to measure isotope ratios and estimate the age of remains.

Major Findings of the Study

• Continuing Natural Selection: The study found that natural selection continued to shape human evolution during the last 10,000 years.
  • Several genetic variants increased or decreased in frequency because of environmental and disease-related pressures.
• Changes in Blood Group Genetics: The frequency of the B blood-group variant increased in Western Eurasia over the last 6,000 years.
  • The A blood-group variant declined during the same period.
• Rise in Coeliac Disease Susceptibility: A variant of the HLA-DQB1 gene associated with coeliac disease increased significantly over the last 4,000 years.
  • Gluten consumption triggers immune attacks on the small intestine in affected individuals.
  • Researchers stated that agriculture alone cannot explain this increase.
• Skin Colour: Humans increasingly selected for lighter skin tones around 8,000 years ago.
  • Lighter skin helped populations living in regions with low sunlight synthesise more vitamin D.
  • Agricultural diets poor in vitamin D may have strengthened this adaptation.
• Evolution of Disease Resistance: The CCR5-∆32 gene variant provides resistance against HIV-1 infection and the frequency of this variant increased thousands of years before HIV emerged.
  • Ancient infectious diseases likely drove the spread of this protective gene.

Significance of the Study

• Understanding Human Adaptation: The study explains how humans adapted to climate change, diseases, agriculture and dietary transformations. It demonstrates that evolution is a continuous and dynamic process.
• Importance for Medical Science: Ancient DNA research improves understanding of immunity, genetic diseases and long-term health patterns.
• Relevance for South Asia: South Asians possess ancestry from Iranian farmers, steppe pastoralists, ancient South Indians and East Asian-related populations.
  • Ancient DNA studies in India can improve understanding of migration, adaptation and disease history.

Concerns

• Risk of Misinterpretation: Genetic findings can be oversimplified or misused to justify racial or cultural superiority.
• Limited Geographical Representation: Most ancient DNA studies are concentrated in Europe and Western Eurasia.
  • Large regions such as South Asia, Africa and Southeast Asia remain underrepresented.

Concluding remarks

• The study demonstrates that human evolution is an ongoing process shaped by climate, diet, disease and environmental pressures.
• Ancient DNA research is transforming understanding of human history, health and biological adaptation.

Source: TH