A study on the sheep's wool provides a deeper explanation as to why some humans have straight hair while others have curly or kinky ones.

Researchers from New Zealand and Japan tried to debunk earlier theories on the composition and structure of curly hair. The study, which was published Thursday in the Journal of Experimental Biology, presented two theories that can be used to analyze hair properties in other mammals including that of human's.

To understand these theories, the researchers analyzed hair samples collected from a merino sheep on a cellular level. The first assumption is that cells on one side of a hair divide more quickly than the other side. As cells continuously divide, a curvature forms which is facing the other side of the hair.

The second theory, proposed by researchers led by Duane Harland, stated two types of cells present in the hair namely orthocortical (longer) and paracortical (shorter) cells. A curvature occurs when a certain number of orthocortical and paracortical cells are arranged on either side of a strand.

Further examination of the cells disproved the first theory because both sides have the same exact number of cells. Harland said it surprised them to discover that the ratio of orthocortical to paracortical does not necessarily equate to the presence of a curvature that results in curly hair.

Although Harland's team's research is inconclusive as to why certain hairs are curly and others are not, it supported their initial findings that the differences between cells are linked to the curvature.

"Most of these theories have very limited or indirect evidence to back them up," said Harland.

Tedious Process

Harland's team of researchers, who previously teamed up with Kao Corporation in Japan, concluded that all hair has the same chemistry and structure regardless if it comes from humans or animals. The process of testing the merino hair underwent a painstakingly tedious process to ensure that the samples are as natural as they can get.

"We had to go to great lengths to make sure we were measuring the natural curvature programmed in during fiber development and not curvature imposed later while the wool was on the sheep's back or during washing and processing," said coauthor David Scobie.

Hair fibers were placed on a vibrating surface to dry them out and to ensure that there are no other materials that will contribute to its kinkiness.

The team took months of carefully counting and measuring the cells and finally concluded that the curl results from the arrangement of the two cell types and not necessarily that one cell is longer or shorter than the other.

Harland is optimistic that their research could go a long way to contribute to the $85 billion hair care industry.