straight when thoroughly doused with water - in a swimming pool, for instance. This is because in these conditions great numbers of hydrogen bonds have been broken. The effect is very temporary, and the hair recovers on drying.

Mixed types
Over many thousands of years these three groups of people have intermingled. Their descendants now show every imaginable blend of hair type and color, as illustrated on pages 43-4, 51 and 53.

Straight or curly?
Of the three racial groups, the Caucasoids are by far the most varied in the appearance of their hair. It may fall completely straight, it may be crinkly or wavy, or it may form large curls, or pretty well anything in between. Blondes tend to have straight hair, while more brunettes have curly hair. The longer the hair grows, the more obvious its basic character becomes. The first month or two's growth of a new hair may be straight, but then it may start to curl or wave.

African hair (electronmicrograph): the longitudinal grooving is very common in this type of hair