Darwin suggested that hairy humans would have risked overheating in the open African savannah, and naked skin cools more easily through sweating. He also suggested that hairlessness might have made our ancestors more sexually attractive to each other.
These ideas could co-exist quite happily with the notion that the need to avoid the bites of parasites helped to drive the evolution of the semi-naked ape. Human fine body hair enhances ectoparasite detection. All rights reserved. Photo of vellus hair by Svdmolen More on human evolution: What is the point of pruney fingers?
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Share Tweet Email. Go Further. Animals Wild Cities This wild African cat has adapted to life in a big city. Animals This frog mysteriously re-evolved a full set of teeth.
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Environment Planet Possible India bets its energy future on solar—in ways both small and big. Environment As the EU targets emissions cuts, this country has a coal problem. Paid Content How Hong Kong protects its sea sanctuaries. Human head hair, like chimp fur, lions' manes and back hair, will only grow to a specific, individually determined length, says Today I Found Out.
That length is determined, in part, by the length of your hair's anagen, or growth, phase. For the hair on your head, the average length of the anagen phase is about years.
For your arms, legs, eyebrows, etc. For these people, their hair never naturally grows more than a few inches long, presumably saving them a significant amount of money over their lifetime on barber visits. Both of these extremes are very rare though. Hair on the head keeps growing for two to six years.
Neufeld and Conroy hypothesize that although the hair follicle itself might be the same, the hair follicle growth cycle must be regulated differently on the head than elsewhere on the body.
But it took someone like Art — who is from outside of the field of anthropology — to ask why different types of human hair apparently have evolved differently.
There is a slight difference in the levels of keratin in human hair. Keratins are fibrous proteins that form the chemical basis of hair, fingernails, rhinoceros horns and other external features of many animals. A potential reason for that difference is a segment of human DNA called a pseudogene. Neufeld and Conroy have ideas about how to identify differences between head hair and fur.
They say studies will be difficult because there can be no animal model for experiments. But they believe it might be possible, for example, to take a human hair follicle from the head and another from the leg and conduct gene-chip experiments to learn about differences in the genes that regulate the activity of those follicles. A similar study involving follicles from the human head and from chimpanzee skin also might provide clues. Human head hair is not fur.
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