• Question: why do people have 5 fingers?

    Asked by epic_ginger to Chloe on 14 Nov 2014.
    • Photo: Chloe Kinsella

      Chloe Kinsella answered on 14 Nov 2014:

      All primates (one exception- spider monkeys) and humans have five fingers on each hand and five toes on each foot. This is an ancient features of mammals called pentadactylism. Humans evolved from primates, so we retained this feature

      Some people have been born with extra fingers. This birth defect, known as polydactyly, is a simple genetic error in the DNA. When errors in DNA occur, sometimes it can cause new features to evolve and this gets passed on to the persons children if it is a useful feature. But natural selection has not gripped onto those extra fingers and made them permanent. Why not? Scientists argue it’s because an extra finger contributes nothing new and so doesn’t give any worthwhile advantage.

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