Hair salons are filled with products that can tame curly locks or enhance them. So the question “what gives curly hair its curl?” seems like one that should be easily Google-able. But there’s no clear answer. Ideas have swirled for decades, and there aren’t a lot of data to back them up.
So scientists decided to look at the microscopic structure of hair. They wanted to count and measure individual hair cells, and human hair was too thick for that. Enter a farm in New Zealand, where researchers sheered wool off of six Merino sheep (pictured)—animals with incredibly fine, naturally curly hair. They stained snippets of these samples and looked at them under a microscope.
Their key finding was that for curly strands of hair, cells on the outside of the curl were much longer than cells on the inside of the curl, the team reports today in the Journal of Experimental Biology. In straighter hair, the outside and inside cells were more similar in length.
It’s not clear whether human hair is subject to the same laws of curliness. But the researchers think the relative length of the outside and inside hair cells probably determines where hair falls on the straight/curly spectrum in humans as well—a discovery that could potentially pave the way for the development of new hair products.