十万个为什么·科学阅读30篇（3）
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Why Do We Have Fingerprints?
人为什么有指纹？
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Fingerprints form before birth in the womb.
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They are patterns of ridges and valleys on skin.
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No two people have the same fingerprints — not even twins.
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Ridges help us hold things better.
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They give more grip on smooth or wet surfaces.
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They also help us feel tiny textures and shapes.
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Police use fingerprints to identify people safely.
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Each finger has a unique pattern that never changes.