The adult human brain weighs about 3 pounds (1,300-1,400 g).
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Oxygen, carbon, hydrogen and nitrogen make up 90% of the human body.
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Yawns are more contagious among people with closer relationships.
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The average person's skin weighs twice as much as their brain.
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Your thumb is about the same size as your nose.
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The largest cell in the human body is the female egg and the smallest is the male sperm.
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An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
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