Is blood ever blue inside the human body?
Human blood is always some shade of red, bright with oxygen and darker without it. Veins look blue because of how light interacts with skin and vessel walls.
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Life sciences
Human Biology
Why are some people left-handed?
Handedness is shaped partly by many genes, each with a small effect, and partly by chance variation in early development. No single cause or left-handedness gene exists.
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