Variations in human skin color are adaptive traits that correlate closely with geography and the sun’s ultraviolet (UV) radiation. As early humans moved into hot, open environments in search of food and water, one big challenge was keeping cool.
Day: August 20, 2025
The war began with Russian tanks invading its sovereign neighbor. Years after Ukraine surrendered its nuclear weapons to Russia in exchange for security guarantees.
— david224 (@david224) August 21, 2025
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