Have you ever wondered why some people have straight, smooth hair, others have curly, curly hair? It turns out, according to a study published in the Experimental Biology Journal in 2018, there are two theories for this phenomenon.
The first hypothesis is that curly hair is due to a large number of hair cells concentrated on the convex side of the hair follicle (the outer edge of the hair strand) and a smaller number of hair cells on the concave side (the inner edge of the hair). Fewer cells make the inner edges shorter, causing the hair to curl inward.
The second hypothesis is that the difference between the length of the hair cells on the convex and concave face is the cause of the curly hair. Similar to the one above, the difference between the length of the outer edge and the inner edge of the hair causes curvature.
In mammals, curly hairs provide better warmth than straight hair. In fact, the straight and curly hairs will intertwine, creating the ultimate line of defense against heat loss.
“The typical plumage structure of a mammal is a forest structure with shrubs,” said lead researcher Duane Harland. He is a senior scientist at AgResearch, one of the largest research institutes of the New Zealand government. Straight hairs “create space close to the skin” and “smaller curly hairs fill that space and keep air inside,” Harland replied.
However, the Harland study only approached the Merino sheep breed. It is difficult to determine if the ability to retain heat is the cause of curly hair in humans. “It’s simply that no one knows human hair well,” Harland said. “Their social aspects and their ability to develop technology have replaced the original biological functions, such as caps, so it is difficult to specify.”
That said, we can still learn a lot about the origin and bioavailability of hair from our furry friends. Because if you go back in time, the hair and hair both came from the same genetic source. “Mammal feathers are ancient,” Harland said. It could have developed before dinosaurs, Harland emphasized. (According to a 2016 study in Scientific Reports, after analyzing 29 skull fossils of several ancient mammals related today, these ancient creatures were furry.) .
To test these two hypotheses, Harland and colleagues used a microscope to enlarge a wool fiber and measure the difference between the number and size of cells on both the inner and outer edges of the hair. Almost immediately, the team found evidence that disproved the hypothesis that the number of cells induces curvature.
“We found evidence that contradicts the theory that the curvature is due to the outer surface having a higher number of cells,” he said. The reason is because in all cases he found that the cells on the outer edge of the hairs were longer, “the finding supports the theory of curvature caused by the difference in cell length,” Harland said.
However, it is not that simple. It doesn’t stop there. “We haven’t looked at a whole hair,” Harland said. His research only observed a portion of wool under a microscope. The curled filament could be for this reason, but also because the torsion force makes a difference in the cell length, which in turn affects the end result, Harland said.
Even if one cut could represent a complete hair, it doesn’t mean that first hypothesis is wrong. It is possible that another type of hair from another animal is bent for another reason.
“Imposing results in all cases is very arrogant,” Harland emphasized.
“That’s why, it takes time to do more research. It would be great if other scientists could simulate or develop our research. Maybe they will find out what is wrong with them,” he said. I hope it’s not a big mistake, but that’s science. “