Asked by: Sergio de Souza, London
So that we can scrunch our hands into a fist, or other complex shapes, without excessive stretching or leaving bags of loose skin – think about how much movement occurs when you’re typing, holding a cup or doing chores. The lines are called ‘palmar flexion creases’ and develop before birth.
Most people have two main lines across the palm but some have a single ‘Simian crease’. This can be inherited normally on either one or both hands, but is also associated with Down’s syndrome and other conditions. Palmistry claims the lines reveal your personality, but there is no evidence for this.