# Why does body hair stop growing at a certain length, but head hair doesn't? **URL:** \ **Category:** Factual Questions\ **Created:** [May 7, 2001, 4:07am UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606 "2001-05-07T04:07:35Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Daemon](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@Daemon](https://boards.straightdope.com/u/Daemon)\ **Post date:** [May 7, 2001, 4:07am UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/1 "2001-05-07T04:07:35Z")
Forgive me if this has been asked and answered before, but it is something that I’ve wondered about for a while. If someone shaves their underarms/legs/pubic area the hair always grows back to approximately the same length. Not so with the scalp/beard, it just keeps on going; even if you’re getting bald, the remainders go on. What mechanism makes body hair stop growing at that point? I used to think is was just hair falling out, then I realized I was losing many more scalp hairs than those from the lower 48! ---
**Author:** ![Max\_Torque](https://avatars.discourse-cdn.com/v4/letter/m/e9bcb4/32.png) [@Max\_Torque](https://boards.straightdope.com/u/Max_Torque)\ **Post date:** [May 7, 2001, 4:21am UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/2 "2001-05-07T04:21:24Z")
Asked and answered, some time ago. [Why does head hair grow indefinitely but other body hair doesn’t?](http://www.straightdope.com/classics/a3_044a.html) ---
**Author:** ![Daemon](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@Daemon](https://boards.straightdope.com/u/Daemon)\ **Post date:** [May 7, 2001, 4:43am UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/3 "2001-05-07T04:43:05Z")
How the hell did you find this? I searched on ‘body hair stop growing’ and came up with zip. Every word I searched on was in the column (except for ‘stop’, but there was ‘stops’, though). And there isn’t a date for the column, it must have been an early one. Anyway, I find the answer unsatisfying (sorry, Cecil). I did get my answer about the mechanics answered, but there is no WHY? And I’m still not convinced about the replacement theory, see the OP. I have seen women with hair almost to the knees (longer than 3 feet, anyway), and then there is the case of Julia Pastrana, the human monkey-woman, exhibited by P. T. Barnum, I believe. ---
**Author:** ![Gozu\_Tashoya](https://avatars.discourse-cdn.com/v4/letter/g/7993a0/32.png) [@Gozu\_Tashoya](https://boards.straightdope.com/u/Gozu_Tashoya)\ **Post date:** [May 7, 2001, 8:20am UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/4 "2001-05-07T08:20:01Z")
You’re more likely to find what you want by entering a fairly generic search term and sorting through the results. In this case, a search for ‘body hair’ (which is what I would’ve used) looks like it would have yielded the thread Max linked to. The opposite goes for web searches, btw. Start as specific as possible and make progressively more general searches as needed. ---
**Author:** ![Sparteye](https://avatars.discourse-cdn.com/v4/letter/s/bbe5ce/32.png) [@Sparteye](https://boards.straightdope.com/u/Sparteye)\ **Post date:** [May 7, 2001, 4:59pm UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/5 "2001-05-07T16:59:57Z")
Daemon, a good explanation why the human body would grow scalp and facial hair of such long length is contained in _The Handicap Principle_, Zahavi & Zahavi (Oxford U Press, 1997). In fact, the theory posited by the authors explains a lot of anomolous physical and behavioral attributes in animals. Briefly and inelegantly: Zahavi & Zahavi propose that certain attributes are displayed as proof of the fitness of the animal. A peacock, for example, has a brightly colored and heavy tail which he displays to attract peahens. The message conveyed is, _“I am so healthy, powerful and smart that I can obtain enough food to grow this beautiful tail, and to drag it around and even fly with it, all while avoiding all the predators to which it makes me so visible and vulnerable. If you want your offspring to be healthy, powerful and smart too, you will mate with me.”_ As to humans and hair, Zahavi & Zahavi suggest that long hair, and the health and grooming it requires, provided a viewable-at-a-distance attestation of the fitness of the wearer. You can find more info about _The Handicap Principle_ here: [http://www.oup-usa.org/publicity/pr\_0195100352.html](http://www.oup-usa.org/publicity/pr_0195100352.html) and here: [http://www.mcn.net/~jimloy/handicap.html](http://www.mcn.net/~jimloy/handicap.html) I recommend the book. The theory answers a lot of puzzles in evolutionary biology, such as hive systems, which no other theories have ever satisfactorily answered. ---
**Author:** ![Sue\_Duhnym](https://avatars.discourse-cdn.com/v4/letter/s/91b2a8/32.png) [@Sue\_Duhnym](https://boards.straightdope.com/u/Sue_Duhnym)\ **Post date:** [May 7, 2001, 6:01pm UTC](https://boards.straightdope.com/t/why-does-body-hair-stop-growing-at-a-certain-length-but-head-hair-doesnt/64606/6 "2001-05-07T18:01:11Z")
> [@](#): > > \*Originally posted by Daemon \* > **And I’m still not convinced about the replacement theory, see the OP.** It’s true, and it does vary greatly from person to person. I had a friend in HS who’s hair stopped right at her shoulders. Well, I mean that was as long as it would grow before going into dormancy. Interestingly enough, the dormancy period (usually) stops during pregnancy. I’ve never had such thick hair, it was great until about three months after I gave birth. It started falling out in clumps, including my body hair. I had a bald spot in my eyebrow, my pubic hair looked like I had mange and my eyelashes even were sparse. Weird shit.