Asked by: Richard House, North Yorkshire
During the first 12 weeks of pregnancy, the developing foetus is making melanocytes – the skin cells that produce ordinary skin colour. These aren’t always evenly spread out: random areas will acquire a cluster and during your life, these clusters can grow into a mole.
Moles are quite different from freckles. Almost everyone has from 30 to 60 moles on their body, but freckles only occur in people with certain genes – particularly the one responsible for red hair. Freckles also need sunlight to trigger them, while moles appear spontaneously.
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Authors
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.
