Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Hair growth.

  1. Sep 3, 2005 #1

    matthyaouw

    User Avatar
    Gold Member

    Why does the hair on our bodies (much like the hair on animals) grow to a certain point, then fall out/stop, but the hair on our heads seems to grow indefinately? Do any other wild animals have hair that can grow forever? I'm not only interested in why it grows in physical terms, but evolutionary terms as well. It doesn't seem to pose much of an advantage that I can think of (actually, now that I'm writing this, shade springs to mind...)
    Thanks.
     
  2. jcsd
  3. Sep 3, 2005 #2
    Scalp hair doesn't grow forever, there's a definite cycle to it. In women the growth phase can last several years, in men it's typically briefer. However, in humans the shedding of scalp hair is desynchronized, unlike "moulting" in animals where it's all shed at once. This desynchronized shedding can make it appear as though human scalp hair grows constantly, it doesn't. Interestingly there does appear to be a mild human "moult" that occurs seasonally.

    Scalp hair has several evolutionary advantages: photoprotection and thermal insulation are the primary ones. I also think (personal opinion here) that scalp hair promotes lymph circulation in the scalp in response to wind exposure.
     
  4. Sep 4, 2005 #3

    matthyaouw

    User Avatar
    Gold Member

    Interesting, thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Hair growth.
  1. Hair questions (Replies: 6)

  2. Growth stunting (Replies: 2)

  3. White/Grey Hair: Twist (Replies: 5)

  4. Blonde hair in offspring (Replies: 10)

  5. DNA in Cut Hair ? (Replies: 10)

Loading...