Daily News Analysis ‘Ancient Human Genomes and Natural Selection ’ : 20 May

Why in News:

• A pioneering genetic survey of ancient West Eurasian skeletal remains has revealed that natural selection significantly altered human gene frequencies, including the ABO blood type variants, over the past 10,000 years.

Ancient DNA and ABO Gene Core Facts:

• Study Scale: Represents the largest temporal survey of ancient human genomes to date, cross-analyzing 15,836 ancient DNA sequences with 6,438 modern genomes using advanced computer simulations.
• Primary Driving Force: Proves that long-term shifts in human gene frequencies across millennia are driven directly by natural selection (survival adaptation) rather than random genetic drift or population migration.
• ABO Gene Dynamics: Human blood types (A, B, O variants) are determined by the ABO gene; the study found that over the last 6,000 years, the B variant rose steadily in frequency among West Eurasians while the A variant simultaneously declined.
• Pathogenic Balance: Because A and B variants trigger opposite biological effects on diverse physical traits, natural selection maintains a fluid balance between them to counter shifting historical disease exposures.
• Celiac Disease and Agriculture: A variant of the HLA-DQB1 (Human Leukocyte Antigen DQ Beta 1) gene that triggers an immune attack against wheat gluten rose from 0% to 20% in the last 4,000 years; this increase occurred independently of the initial rise of agriculture.
• Vitamin D and Skin Pigmentation: Approximately 8,000 years ago, selective pressures favored gene variants for lighter skin and hair tones to facilitate optimal Vitamin D synthesis in low-sunlight regions, particularly among early farmers with grain-heavy diets.
• South Asian Genetic Context: South Asian populations possess a highly diverse genetic legacy consisting of ancestral Iranian Neolithic Farmers, Western Steppe Herders, Indigenous Eastern Eurasians (Ancient Ancestral South Indians), and East/Southeast Asian lineages.