Naked love: Here’s a the­ory about why you aren’t cov­ered in fur

Vancouver Sun - - OPIN­ION - BY JAMES GILES James Giles is a Canadian philoso­pher based at La Trobe Univer­sity in Aus­tralia. His ar­ti­cle ‘ Naked Love: the Evo­lu­tion of Hu­man Hair­less­ness’ has just been pub­lished in the June is­sue of the journal Bi­o­log­i­cal The­ory. Post­media News

Hu­man be­ings are the only pri­mates who lack a thick coat of fur. This sug­gests that the pri­mate an­ces­tors of hu­man be­ings also had fur and in the course of evo­lu­tion lost it. Of course we also have body hair, but it is for the most part so fine and short as to be nearly in­vis­i­ble and thus to ren­der us vir­tu­ally naked. But why should we lose our body hair while all other pri­mates re­tained theirs?

Although there are nu­mer­ous the­o­ries, none of them seems fully ad­e­quate. One of the prob­lems that many of the the­o­ries share is they only con­sider evo­lu­tion from the per­spec­tive of the adult. But in­fants are also un­der the pres­sures of evo­lu­tion. Look­ing at the sit­u­a­tion of the an­ces­tral in­fant pro­vides some clues to this puz­zle. The an­swer, I want to ar­gue, is that hair­less­ness ap­peared in the con­text of the an­ces­tral mother-in­fant re­la­tion­ship by en­cour­ag­ing the ma­ter­nal de­sire to hold the in­fant. It was then re­in­forced in male-fe­male sex­ual re­la­tions.

To see how this came about, let us start by not­ing that the driv­ing fac­tor in hu­man evo­lu­tion seems to be bipedal­ism or the abil­ity to walk on two legs. Bipedal­ism had many ad­van­tages. How­ever, there were also many costs for this new-found abil­ity. One of the great costs was the loss of feet that could grasp.

This was not a ma­jor prob­lem for older in­di­vid­u­als since they would have then spent most of their time on the ground. How­ever, it was a prob­lem for in­fants be­cause tree-dwelling an­ces­tral in­fants, like all other pri­mates, would have only sur­vived by be­ing able to grasp the fur of their mothers with their hands and feet.

The fact that, like all other pri­mates, our an­ces­tors also grasped their mothers’ fur is sug­gested by the grasp­ing reflexes that are still present in hu­man in­fants. If one places a fin­ger in the hand of a new­born it re­sponds by grasp­ing the fin­ger. Or if a new­born’s feet are touched it re­sponds by curl­ing the toes in what looks like a grasp­ing mo­tion. But why should a hu­man in­fant have such reflexes? A likely an­swer is they are the ves­tiges of an an­cient re­flex to grasp the mother’s fur.

Luck­ily, how­ever, the in­fant’s lack of abil­ity to hold onto the mother could be com­pen­sated for by the mother’s abil­ity to hold onto the in­fant. For one of the re­mark­able ad­van­tages of bipedal­ism is that it frees the arms to carry things.

How­ever, the mother’s abil­ity to hold the in­fant was only part of what was needed. The other part was the mother’s strong de­sire to hold the in­fant. Con­tin­u­ally clutch­ing an in­fant is hard work. One can imag­ine that many of our early an­ces­tors found the task so daunting that they fre­quently put the in­fant down while they did other things, only to have it snatched by a preda­tor or swarmed by in­sects. Clearly, any­thing that aided in strength­en­ing the ma­ter­nal de­sire to hold the in­fant would have been se­lected for. But what fac­tors could have strength­ened such a de­sire?

An an­swer is the in­ti­macy and warmth of skin-to-skin con­tact with the in­fant. Many women re­port plea­sure in such con­tact, es­pe­cially in breast­feed­ing. A large per­cent­age of mothers feel sex­u­ally aroused dur­ing breast­feed­ing, with some even re­port­ing or­gasms. Also, mothers who breast­feed their in­fants with naked con­tact re­port higher amounts of af­fec­tion­ate love for their in­fants than do those who breast­feed with­out such con­tact. Fur­ther, re­search shows that in­fants in skin-to-skin con­tact with their mothers dur­ing breast­feed­ing are more re­laxed, cry less, and breast­feed longer that do in­fants lack­ing naked con­tact. Ob­vi­ously, th­ese are all fac­tors that strengthen the hu­man ma­ter­nal de­sire to hold the in­fant. It seems likely the same would have been true for our bipedal an­ces­tors.

Plainly, how­ever, skin-to-skin con­tact here is only pos­si­ble be­tween a hair­less mother and a hair­less in­fant. Con­se­quently, naked skin would have been se­lected for as some­thing that strength­ened the an­ces­tral mother’s de­sire to hold the in­fant. This evo­lu­tion­ary mech­a­nism, which I call ma­ter­nal se­lec­tion, also helps to ex­plain why women are more hair­less than men.

Male adult hair­less­ness, which is less ex­ten­sive, would prob­a­bly have evolved through ge­netic cor­re­la­tion with fe­male hair­less­ness.

How­ever, in the naked love the­ory, ma­ter­nal se­lec­tion is only one mech­a­nism that se­lects for hair­less­ness. The other is sex­ual se­lec­tion, that is, the process of an in­di­vid­ual choos­ing a sex­ual part­ner on the ba­sis of the in­di­vid­ual’s sex­ual at­trac­tive­ness. In this view, hair­less in­di­vid­u­als would have been seen as more sex­u­ally at­trac­tive than hair-cov­ered in­di­vid­u­als ( Sex­ual se­lec­tion prob­a­bly also ex­plains the ex­is­tence of long fe­male head hair, and of both male and fe­male un­der­arm and pu­bic hair, which trap sex­ual scents and draw at­ten­tion to the gen­i­tals. The preva­lence of male pat­tern bald­ness sug­gests that male head hair was not se­lected for but, like male nip­ples, was merely ge­net­i­cally passed on to males from fe­males).

It seems clear that a baby who en­joyed hair­less skin-to-skin con­tact with his or her mother would seek to recre­ate such con­tact as an adult with a hair­less sex­ual part­ner. This would have es­pe­cially been the case for an­ces­tral males since the in­creased fe­male vul­ner­a­bil­ity with hav­ing to carry and tend to in­fants would have meant that it was the males who were pri­mar­ily ex­er­cis­ing sex­ual se­lec­tion.

One of the ad­van­tages of the naked love the­ory is that it helps to ex­plain the evo­lu­tion­ary ori­gins of ro­man­tic love. This can be seen by com­par­ing hu­man sex­ual and at­tach­ment be­hav­iours with those of our clos­est fur-bear­ing rel­a­tives. One of the things that dis­tin­guishes us here is the in­ten­sity and du­ra­tion of sex­ual in­ter­course. While sex­ual in­ter­course for the chim­panzee lasts for a mere seven sec­onds, for hu­mans it is typ­i­cally about 10 min­utes. That is 85 times longer. One of the rea­sons for this is the ex­ten­sive skin-to-skin con­tact, fondling, and ca­ress­ing we of­ten use in sex­ual in­ter­course. Clearly, this is only pos­si­ble be­cause of naked skin.

The in­ti­macy and warmth of skin-to-skin con­tact with an in­fant likely in­creased the de­sire of our an­ces­tors’ moth­ers to hold and pro­tect their ba­bies.

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