Adaptive Genetics Across Human Populations

Humans are one species, but natural selection has fine-tuned our populations for local environments. Genes that influence diet, skin pigmentation, immunity, and even high-altitude physiology reveal how different groups adapted in unique ways.

Comparative Table of Human Populations and Adaptive Genes

Population	Adaptive Traits	Key Genes Involved	Notes
Europeans	Lactose tolerance, skin pigmentation, immunity	LCT (lactase persistence), SLC24A5, SLC45A2, HERC2/OCA2	Lactase persistence is a recent adaptation (~7,500 years ago) tied to dairying culture.
East Asians	Alcohol metabolism, starch digestion, skin/hair morphology	ALDH2, ADH1B, AMY1 copy number, EDAR	EDAR variant affects hair thickness and sweat glands, unique to East Asians.
Africans	Skin pigmentation, malaria resistance, immunity	MC1R, G6PD, DARC, HBB (sickle cell), APOL1	Classic case of balancing selection: sickle cell allele protects against malaria but causes sickle cell anemia.
Tibetans (High Altitude)	Hypoxia tolerance	EPAS1, EGLN1	EPAS1 allele likely introgressed from Denisovans, enabling survival at high altitude.
Andean Highlanders	Increased red blood cell count, oxygen transport	EGLN1, PRKAA1	Distinct strategy from Tibetans: they boost hemoglobin rather than reduce hypoxia response.
Greenlandic Inuit	Fat metabolism, diet adaptation	FADS1, FADS2	Adapted to a high-fat marine diet rich in omega-3 fatty acids.

Evolutionary Insights

🔹 While all humans share ~99.9% of their DNA, these adaptive alleles show how small genetic differences shaped big survival strategies. 

 🔹 High-altitude adaptations in Tibetans vs. Andeans highlight convergent evolution—different genetic solutions to the same environmental challenge. 

 🔹 Some adaptive alleles (EPAS1 in Tibetans) were acquired via archaic introgression from Denisovans.

Why This Matters

Studying these genes sheds light on human history, migration, and survival strategies. It also connects to medicine—for example, variants that protected against past infections may predispose modern populations to hypertension, diabetes, or other chronic conditions in new environments.