Depending on the current fashion, curly hair can be a blessing or a curse: people often spend a fortune taming unmanageable curls or sculpting luxurious waves.
However, despite decades of research, it was still not clear why hair curls naturally.
Duane Harland from AgResearch, New Zealand says that there were two competing theories. As individual hairs are made up of two different cell types – paracortical cells (which are packed with parallel keratin fibres) and orthocortical cells (which are packed with twisted keratin fibres) – one theory suggested that the longer orthocortical cells would line the outer side of the curve, with paracortical cells lining the inner side.
The alternative theory suggested that there were more cells on the outer side of the curl, because the cells on that side of the hair follicle divided more, increasing the number of cells in the outer curve of the curl. 'But most of these theories have very limited or indirect evidence to back them up', says Harland.
Having worked previously with Japan's Kao Corporation cosmetics company to learn more about the structure of human hair, Jolon Dyer and Stefan Clerens teamed up with Shinobu Nagase, Takashi Itou and Kenzo Koike to get to grips with the knotty problem of what makes hair curly.