why do we have extragrowth of hair only on our head but not on other parts of our body?

Answer 1

The type of hair which grows on your scalp is termed terminal hair. This hair is more coarse, thicker, and is genetically programmed to grow longer than the vellus hair found elsewhere on your body. Vellus hair is also termed "peach fuzz". However, when an individual reaches adrenarche, puberty, the addition of thick, coarse androgenic hair is observed. The term androgenic comes from the influence of androgen's, hormones such as testosterone, on hair, oil secreting glands, and sweat ducts. Since males have increased testosterone production the observation of additional hair on the face, chest, back, and thicker hair on the arms and legs is seen over females. Additionally, while the hair on your head, and face, continues to grow, the androgenic hair reaches a certain length and ceases to grow.

Since a great majority of our heat dissipation occurs through our scalp (noticeable when you sweat while wearing a hat in cold weather and take the hat off, steam develops), the excess of hair acts to insulate, impeding heat loss. As stated by a previous reply some people, typically men due to varying testosterone levels, have quite an abundance of body hair. A possible explanation of this is an ancestry from a very cold environment or the more obvious, more circulating testosterone.

In short, the amount of hair depends on genetics and thus hormonal stimulus

Answer 2

According to Richard Dawkins most of the human traits are due to sexual selection as against Natural selection. The sexual dimorphism in animals are mainly due to sexual selection or the mate selection.
The second plausible reason is as hominids chose bipedal movment, the erect walking mode, the head become the focul point for sun rays. In order to cut the amount of UV rays hitting the scalp, the head retained the hairs.
The remaining parts of the body lost hairs due to mate preferences.

Answer 3

Uneven growth of hair in human forms is one of the distinguishing characters, taxonomically speaking. There are a number of reasons for this. Some of them have been given by other answerers. In man sexual selection is not predominant as said and quoted in this section. In man sexual selection is passive unlike animals in which it assumes a dominant role. The appearance and body strength are shadowed by other human qualities and qualifications. One can get attracted not really by looks but by other deep-seated qualities, and they constitute equally cogent consideration for selecting a mate.
Coming back to the main question, you have to address this to the genes. In some regions of the body hair has become vestigial because of the differential inactivation of genes responsible for the growth of hair. In future hair may altogether vanish like whales, to be seen only in the embryonic condition.

Answer 4

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Answer 5

That is a good question! I think it is to protect us from the suns "harmful" rays. You really dont need that kind of protection on any other part of your body so i think thats why it doesnt grow that thick anywhere else. unless you are pre-genetically desposed to looking like an ape! just joking!

Answer 6

It has been suggested that man is the aquatic ape. If true, since we keep our heads above water most of the time, it would be the one place where bare skin would not be needed or wanted. Remember, dolphins and whales are basically hairless, too.

Answer 7

bcus there are extra and numerous glands for hair production in the head and less in the other parts of the body

Answer 8

I don't know, I've always wondered that. After all, we don't generally trim the hair on our arms, but they don't get as long and thick as the hair on our scalps. Who knows?

Answer 9

i dont know about you but all my hair is pretty even out. including my head.

Answer 10

not all true some have coase hair on the butt and on privatesalso on chest and back havent you seen the commercials?