# Why have humans "de-evolved" hair? **URL:** \ **Category:** Factual Questions\ **Created:** [April 20, 2003, 4:13am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780 "2003-04-20T04:13:34Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 20, 2003, 10:34pm UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/21 "2003-04-20T22:34:16Z")
DF: The soft hair is called “lanugo”. I’ve read about it in lots of books on human evolution, but don’t have an actual cite for you. It could be something completely differenct. Not sure if, for example, apes’ body hair starts off as “simian lanugo”. If not, then it might be a totally different thing in humans. I’ll do a little google searching later on today and see if I can come up with something. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [April 20, 2003, 10:36pm UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/22 "2003-04-20T22:36:18Z")
Do other primates sweat? If not, that might be a starting point for an answer to the OP. The only other sweaty animal of which I am aware is the horse, which has very short hair as a rule. I’m guessing this makes it easier for the sweat to evaporate, and makes perspiration a more effective cooling adaptation. ---
**Author:** ![Susanann](https://avatars.discourse-cdn.com/v4/letter/s/7ab992/32.png) [@Susanann](https://boards.straightdope.com/u/Susanann)\ **Post date:** [April 20, 2003, 11:07pm UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/23 "2003-04-20T23:07:31Z")
So those who believe in evolution must believe that females have evolved higher than males? ---
**Author:** ![scott\_evil](https://avatars.discourse-cdn.com/v4/letter/s/91b2a8/32.png) [@scott\_evil](https://boards.straightdope.com/u/scott_evil)\ **Post date:** [April 20, 2003, 11:28pm UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/24 "2003-04-20T23:28:16Z")
It seems a significant percentage of the gay male community has wilfully de-evolved pubic hair. :rolleyes: ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 21, 2003, 1:05am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/25 "2003-04-21T01:05:11Z")
For info on the Aquatic Ape Hypothesis, one need go no farther than our very own site. **bibliophage** wrote a marvellous [Staff Report](http://www.straightdope.com/mailbag/maquaticape.html) on it. ---
**Author:** ![Biggirl](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/biggirl/32/3294_2.png) [@Biggirl](https://boards.straightdope.com/u/Biggirl)\ **Post date:** [April 21, 2003, 1:20am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/26 "2003-04-21T01:20:57Z")
From [A Moment of Science.](http://amos.indiana.edu/library/scripts/lanugo.html) > [@](#): > > Those barely-there hairs that fall out after the baby is born are probably lanugo hairs. Soon after the hair follicles are produced in the womb, they sprout the body’s first hair–lanugo hair, which covers us from head to toe. It’s characterized by its lack of pigmentation and for being ultra fine and soft. Then at about eight months into gestation most people lose their lanugo hair, so that it may be replaced by two new kinds of hair, vellus and terminal hair–the kinds of hair we will have for the rest of our lives. My doctor told me these hairs may be responsible for late pregnancy nausea. ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [April 21, 2003, 2:36am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/27 "2003-04-21T02:36:58Z")
The question is based on a premise that is not true. That premise being that we evolved from apes. We don’t know that our ancestors, and those of apes were as hairless as we are or as hairy as a gorilla. The common ancestor could have easily been relatively hairless, and the subsequent divisions that became apes developed hair, whereas our division did not. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 21, 2003, 3:39am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/28 "2003-04-21T03:39:16Z")
Sigene: We do know that hairiness is the norm for mammals. Wouldn’t it be strange if our ape or pre-ape ancestors lost their hair, then all the remaining apes (except us) seperately evolved to a hairy state again? While your scenario is certainly possible, it’s extremely improbable. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [April 21, 2003, 5:27am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/29 "2003-04-21T05:27:13Z")
According to [this site](http://www.neoteny.org/a/heterochrony1.html) (note that heterochrony is a more inclusive term which includes both neoteny and _progenesis_, a process in which the retention of juvenile features is achieved by cutting short development - rather than prolonging it - by reaching sexual maturity progressively earlier), > [@](#): > > One of the most interesting cases of this kind is that of the hair, for Bolk has shown that a progressive series in reduction can be made out in the monkeys, apes, and man: 1. the monkey is born with a complete covering of hair; 1. the gibbon is born with the head and back covered with hair, and the other regions are covered later; 3. the gorilla is born with the head covered with hair, and the other regions are partially covered later; 4. man is born withhead [sic] covered with hair, and the other regions are scarcely covered at all later. It is noted that the lanugo, which forms a very fine covering to the unborn infant before being lost, is also present in unborn apes. Further, the lanugo is retarded in man, for he has not completely shed it by the time of birth. This series shows that the neoteny of man as regards hair is associated with a progressive retardation in the rate of its development. This retardation in the rate of development of the body, it will be remembered, is all that is required to produce the other human features mentioned above. Of note is the fact that a) the lanugo is also present in other apes, and b) even the development of the lanugo is slowed with respect to those apes. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [April 21, 2003, 5:28am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/30 "2003-04-21T05:28:21Z")
Oh, and thanks **John Mace** and **Biggirl** for the info about lanugo - I’ve learned something! 🙂 ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 21, 2003, 5:46am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/31 "2003-04-21T05:46:58Z")
DF: Thanks for the site. I’ll have to take some time tomorrow to read it more thoroughly. On first take, this: “the lanugo is retarded in man, for he has not completely shed it by the time of birth.” sounds more like apes are neotenous wrt to lanugo and humans aren’t. I’m sure that can’t be right-- it must be getting late. ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [April 21, 2003, 5:50am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/32 "2003-04-21T05:50:01Z")
as soon as I hit the submit button, it made sense. Of course, retention of a fetal condion after birth is neoteny. It IS getting late… ---
**Author:** ![ronbo](https://avatars.discourse-cdn.com/v4/letter/r/ba9def/32.png) [@ronbo](https://boards.straightdope.com/u/ronbo)\ **Post date:** [May 15, 2003, 11:56pm UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/33 "2003-05-15T23:56:33Z")
The answer was on television tonight: _The Life of Mammals with David Attenborough_ It showed a bushman running down an antelope. The Bushman could sweat and replenish his sweat with carried water. The antelope could do neither. After eight hours, the antelope evenutally collapsed out of exhaustion and heat stroke. Throwing the spear was almost unnecessary. We lost our hair so we could sweat. We could afford to sweat becuse we could carry water. We could carry water because we walked upright and had our hands free; we could carry water because because we were intelligent. The less hairy and sweatier and more intelligent had more food for their families. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [May 16, 2003, 12:07am UTC](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780/34 "2003-05-16T00:07:01Z")
Of course humans don’t need to carry water in order to be able to run. Even without drinking a moderately fit human will happily run for an hour without suffering more than minor dehydration. Most mammals don’t sweat at all, and we have a different type of sweat gland to those few that do. Human glands produce sweat over a prolonged period. Other mammals tend to sweat in short bursts and then the sweat glands are depleted. Once you chase such an animal beyond the limit of ots sweat glands it begins tto overheat. I’m surprised it took 8 hours to run down a gazelle. That’s a long time for an non-human animal to run for. [Previous page](https://boards.straightdope.com/t/why-have-humans-de-evolved-hair/169780.md?page=1)