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I am a caucasian man and I lived out in the woods for several years during which I didn’t cut my hair and only washed with lake water, didn’t brush my hair and it grew perfectly straight and un-knotted. I massaged my scalp regularly and ran my fingers through my hair to spread the oil around.
Dreadlocks and knots actually appear actually caused by washing with hot water and/or soap. Since my hair has the natural oils it doesn’t knot up at all. When I came away from living in the woods to work on a farm instead, at first I would wash my hair with warm water, and very quickly it started knotting and snapping, and lost its sheen and colour. It was quite upsetting for me. The hair also became loose/separated and got in my eyes and stuff, and since it snapped easily there were short bits which wouldn’t tie back.
Now I just wash it with luke-warm water and keep soap away from it, and it is starting to get its colour and sheen back very slowly, whilst knotting and snapping less and less.
With the natural oils I expect I can synthesise vitamin D in my hair, which would be one advantage, especially since most of our skin is covered up by clothes. Furry animals synthesise vitamin D in the oils on their fur.
I really have long hair just because ‘what if’: what if there is some benefit to having it which outweighs the downsides. I’ve chosen to take that gamble so far. I’m a logical, scientific person, but there has just been virtually no study into possible benefits of long hair. Since I was into the natural stuff, growing long hair seemed an appropriate thing for me to try out.