It is common for some writers to refer to humans as “naked apes” in reference to the fact that our bodies are not covered with fur. In her chapter in Becoming Human: Our Past, Present and Future, Nina Jablonski writes:
“Among primates, humans are unique in having nearly naked skin. Every other member of our extended family has a dense covering of fur—from the short, black pelage of the howler monkey to the flowing copper coat of the orangutan—as do most other mammals. Yes, we humans have hair on our heads and elsewhere, but compared with our relatives, even the hairiest person is basically bare.”
Many hypotheses have been offered to explain why humans are basically naked. In his book The Origins of Language: A Slim Guide, James Hurford writes:
“There is no completely satisfactory explanation for the move to nakedness. Possibly it helped keep the animals cool in the hot savannah, or perhaps sexual selection favoured a bare skin. The skin colour at this time may have been light, like chimpanzee skin under the fur, and quickly evolved blackness to protect against the African sun.”
In her chapter in The Story of Us, Nina Jablonski writes:
“Early human ancestors are believed to have had pinkish skin covered with black fur, much as chimpanzees do, so the evolution of permanently dark skin was presumably a requisite evolutionary follow-up to the loss of our sun-shielding body hair.”
One of the genes responsible for producing skin pigmentation in humans is MC1R. The variant of this gene found found in Africans with dark pigmentation originated about 1.2 million years ago. With regard to the evolution of the white skin color generally associated with today’s Europeans, the data from biological anthropology suggests that this was a recent development and seems to be associated with the Bell Beaker culture (2700 BCE to 2000 BCE). This means that the human remains found in Gough’s Cave in Britain, which date to the Mesolithic era (10,250 years ago), probably had dark skin rather than the white skin of his modern English descendants.
In his book Ancestors in Our Genome: The New Science of Human Evolution, Eugene Harris writes:
“The loss of body hair played an important role in our evolution, allowing early ancestors to adjust their body temperatures efficiently and to gather and hunt widely for food.”
Having a body covered with hair (or fur) is one of the defining characteristics of mammals. Those mammals which have the least amount of body hair are marine mammals who live in water and those mammals which live underground. One of the explanations for human nakedness is the aquatic ape hypothesis that claims that humans were once aquatic animals, and this explains why we don’t have fur today. Another hypothesis claims that human ancestors once lived underground. Neither of these hypotheses has generated much support from scientists who study human evolution Nina Jablonski writes:
“Human hairlessness is not an evolutionary adaptation to living underground or in the water—the popular embrace of the so-called aquatic ape hypothesis notwithstanding. Neither is it the result of large body size. But our bare skin is related to staying cool, as our superior sweating abilities suggest.”
Humans have and abundance of hair in two readily visible places: on top of the head and in the pubic area. With regard to head hair, Nicholas Wade, in his book Before the Dawn: Recovering the Lost History of Our Ancestors, reports:
“Human head hair differs from that of apes in that it never stops growing.”
In her chapter in The Story of Us, Nina Jablonski writes:
“As for hair on the head, it was most likely retained to help shield against excess heat on the top of the head. That notion may sound paradoxical, but having dense hair on the head creates a barrier layer of air between the sweating scalp and the hot surface of the hair.”
The presence of head hair and pubic hair suggests the possibility that hair in these locations may be the results of sexual selection. It may also provide a clue as to how long human ancestors have been without fur. In his book The Gap: The Science of What Separates Us from Other Animals, Thomas Suddendorf explains:
“The pubic louse, DNA comparison suggests, migrated to our ancestors some 3.3 million years ago. The closest relative to the human pubic louse is the louse specialized on gorillas, so we apparently got crabs from the ancestors of gorillas. More importantly what this finding means is that 3.3 million years ago our head and pubic hair were already sufficiently separated by hairless body regions to enable two types of lice to live in distinct habitats on the same host.”
With regard to the function of hair, Desmond Morris writes: “The most likely explanation is that the bizarre human hair pattern acts as a species flag—a display that set us apart from all our close relatives (relatives that we have long since eliminated).” Morris also writes:
“In their primeval condition, our remote human ancestors, with their naked bodies and long head hair, could be spotted far off in the distance, and easily differentiated from their furry-bodied cousins.”
With regard to head hair, Nicholas Wade writes:
“In every society in the world, people spend an inordinate amount of time in cutting, shaping, braiding, plaiting, curling, straightening, decorating and otherwise gussying up the appearance of their hair.”
With regard for caring for hair, Desmond Morris writes:
“Just how our remote, primeval ancestors managed to cope with these extravagant hair patterns, before they had invented knives, scissors, combs and other grooming tools, is never discussed by anthropologists, perhaps because they have no answer.”
Viewing head hair as a secondary sexual characteristic, head hair can be seen as the result of sexual selection in evolution. In his book The Accidental Species: Misunderstandings of Human Evolution, Henry Gee writes:
“What is head hair for? There seems no good, adaptive reason for the presence of hair on the head (as opposed to anywhere else) than sexual selection, and this illustrates how secondary sexual characteristics need have no adaptive function except that they are attractive to the opposite sex…”
With regard to the evolution from fur to being naked, Judith Rich Harris writes in What We Believe but Cannot Prove: Today’s Leading Thinkers on Science in the Age of Uncertainty:
“I believe (though I cannot prove it) that the transition to hairlessness took place quickly, over a short evolutionary time period, and involved only Homo sapiens or its immediate precursor.”
The loss of body hair in human evolution may be connected to other anatomical and cultural changes, including the large brain, symbolism, and language. In her chapter in The Story of Us, Nina Jablonski writes:
“The loss of most of our body hair and the gain of the ability to dissipate excess body heat through eccrine sweating helped to make possible the dramatic enlargement of our most temperature-sensitive organ, the brain.”
More Human Origins
Human Origins: Domesticating Fire
Human Origins: Menopause
Human Origins: The Alphabet
Human Origins: The Great Chain of Being
Human Origins: The Mind
Human Origins: Bipedalism
Human Origins: Sex
Human Origins: Symbolism