Comments on: Why are humans (mostly) hairless? http://alistairpott.com/2009/09/21/why-are-humans-mostly-hairless/ Wed, 02 May 2012 01:08:00 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: alistairpott http://alistairpott.com/2009/09/21/why-are-humans-mostly-hairless/comment-page-1/#comment-2468 alistairpott Fri, 18 Feb 2011 07:36:00 +0000 http://alistairpott.com/?p=867#comment-2468 Great comment and interesting point. I suspect that our remaining hairs do provide an advantage through tactile perception. The obvious question though is why only humans? If the thin coat were such an advantage why would (pretty much) only humans have evolved this approach? Since only humans evolved this trait there must be another factor that is not taken into account in your theory. Even in warm climates other land mammals have thick coats rather than taking advantage of your theory. Why? This suggests that the theory that humans evolved a thinner coat for increased tactile perception is at best incomplete. Great comment and interesting point. I suspect that our remaining hairs do provide an advantage through tactile perception.

The obvious question though is why only humans? If the thin coat were such an advantage why would (pretty much) only humans have evolved this approach?

Since only humans evolved this trait there must be another factor that is not taken into account in your theory. Even in warm climates other land mammals have thick coats rather than taking advantage of your theory. Why?

This suggests that the theory that humans evolved a thinner coat for increased tactile perception is at best incomplete.

]]> By: Ken Fabos http://alistairpott.com/2009/09/21/why-are-humans-mostly-hairless/comment-page-1/#comment-2467 Ken Fabos Thu, 17 Feb 2011 22:56:00 +0000 http://alistairpott.com/?p=867#comment-2467 I've had a longstanding problem with most of the theorising about human 'hairlessness' - the failure to recognise and take into consideration one of the most basic functions of hair; it's sensory function. We get tactile sensory information via our hairs - presence of insects, close encounters with solid objects, air movements. This tactile sense can extend well beyond the surface of the skin. Around the eyes and ears the hairs are extremely sensitive, even (especially?) the hairs so fine as to be near invisible. What many people perceive as direct skin contact is often contact with hairs; in my own case an insect has to struggle to reach skin on arms and legs and I feel them from the moment they disturb the hairs. With respect to it's evolution, sparser, finer hairs are (all else being equal) more sensitive than denser, heavier hairs. This is basic physics, not biology; being sparser means vibration and movement of hairs is not dampened and dissipated so much by being laid up against other hairs. Being finer means they are moved and vibrated by smaller impulses. This gives a lower sensory threshold to sparse fine hairs than to hairs that are part of a thick pelt. I would also point out that goosebumps, by separating the individual hair shafts, would increase sensitivity as well as extend the sensory reach to it's maximum. When our ancestors lost their thick coat, they gained greater tactile sensitivity. Until the scholars who study and theorize on the evolution of human hair recognise and take into considerations all of it's existing functions I don't believe their speculations should be taken too seriously. I’ve had a longstanding problem with most of the theorising about human ‘hairlessness’ – the failure to recognise and take into consideration one of the most basic functions of hair; it’s sensory function. We get tactile sensory information via our hairs – presence of insects, close encounters with solid objects, air movements. This tactile sense can extend well beyond the surface of the skin. Around the eyes and ears the hairs are extremely sensitive, even (especially?) the hairs so fine as to be near invisible. What many people perceive as direct skin contact is often contact with hairs; in my own case an insect has to struggle to reach skin on arms and legs and I feel them from the moment they disturb the hairs.
With respect to it’s evolution, sparser, finer hairs are (all else being equal) more sensitive than denser, heavier hairs. This is basic physics, not biology; being sparser means vibration and movement of hairs is not dampened and dissipated so much by being laid up against other hairs. Being finer means they are moved and vibrated by smaller impulses. This gives a lower sensory threshold to sparse fine hairs than to hairs that are part of a thick pelt. I would also point out that goosebumps, by separating the individual hair shafts, would increase sensitivity as well as extend the sensory reach to it’s maximum. When our ancestors lost their thick coat, they gained greater tactile sensitivity.
Until the scholars who study and theorize on the evolution of human hair recognise and take into considerations all of it’s existing functions I don’t believe their speculations should be taken too seriously.

]]>