Animal claws, human nails, hair, growth, degradation and the misc of it (phew!)
Get answers on:
– Animals have claws, why do humans have nails?
– What are nails made up of?
– Are nails and hair degradable?
– How quickly does your hair grow?
– Why do we have hair on our body?
– What does actually happen when your hair turns grey/ white?
all this and lots more…
First, on why we have nails…
Without nails, wouldn’t you have a hard time scratching an itch… or untying a knot… you may have to bite your fingers to relieve tension! As for the claws… can you visualize a tiger tearing its prey apart with nails.. or a falcon diving and clutching its prey with nails? Just doesn’t seem right, does it? Thats why humans have nails and animals don’t.
Technically, a nail is similar to a claw, but with a curved edge. A nail that is big enough to bear weight is called a ‘hoof.’ True claws — found in reptiles, birds, and mammals — consist of a dorsal scalelike plate (unguis) covering a ventral plate (subunguis), the whole capping the bony tip of a digit. Nails—found only in mammals—consist of a broad and flattened unguis, with the subunguis reduced to a vestige under the outer tip.
Much like the tail, the claw in apes was no longer necessary as other appendages evolved better so claws disappeared over a period of time. The debate is on whether nails or claws were present on the digits of the last common ancestor of living primates.
Did you know: Nail tools used by different people in salons may transmit infections. They may spread nail fungi, staph bacteria or viruses. In fact, over 100 bacterial skin infections in 2000 were traced to footbaths in nail salons. To avoid this, new improved contactless tools can be used, for example, gel and cream cuticle removers instead of cuticle scissors.
One gesture common in the West is to breathe on one’s fingernails, then polish them on one’s clothing. This means either “I have done something really good” or “you are so boring I am polishing my nails rather than listen to you.”
Everything else about nails:
Nails are made up of a tough protein called Keratin and are produced from living skin cells in the fingers and toes. The free edge is the part of the nail that extends past the finger, beyond the nail plate. There are no nerve endings in the nail – this is the growing part of the nail still under the skin at the nail’s proximal end.
Nails grow at an average rate of 3 millimetres a month. Fingernails require 3 to 6 months to regrow completely. Toenails require 12 to 18 months. Actual growth rate is dependent upon age, season, exercise level, and hereditary factors. Contrary to popular belief, nails do not continue to grow after death; the skin dehydrates and tightens, making the nails (and hair) appear to grow.
Hair today… gone tomorrow?
Hair is present in differing degrees on all mammals, and its most important function in those other than human is to conserve body heat by insulating against cold. Humans are the most hairless of all mammals, and yet hair occupies a central place in human development and sense of self. Whether it is the gradual decrease of hair leading to male baldness, the loss of pigment leading to white or grey hairs and signalling the onset of middle age, or the adolescent desire for the pubic hair that signals approaching adulthood, hair often tells others something about our place in culture.
Some people think that a big shock or trauma can turn a person’s hair white or gray overnight, but scientists don’t really believe that this happens. Just in case, try not to freak out your parents too much. You don’t want to be blamed for any of their gray hairs!
On the scalp, where hair is usually densest and longest, the average total number of hairs is between 100 000 and 150 000. Human hair grows at a rate of 10-13 mm/month.
As for the degradation, yes… all human parts degrade. If that wasn’t the case, wouldn’t we be left with our ancestor nails and hair in bulk? Not an appealing picture.
Hair is not an easily degradable substance; there are instances of hair being found that is thousands of years old (i.e. Egyptian mummies) The hair shafts may also store certain poisons for years, even decades, after death. In the case of Col. Lafayette Baker, who died July 3, 1868, use of an atomic absorption spectrophotometer showed the man was killed by white arsenic. The prime suspect was Wally Pollack, Baker’s brother-in-law. According to Dr. Ray A. Neff, Pollack had laced Baker’s beer with it over a period of months, and a century or so later minute traces of arsenic showed up in the dead man’s hair. Mrs. Baker’s diary seems to confirm that it was indeed arsenic, as she writes of how she found some vials of it inside her brother’s suitcoat one day.
Hair survives in diverse archaeological environments, yet it is not found universally. The fact that hair degrades means that the complex interaction of hair with its depositional environment must be considered. The tip and root ends of the fibres are more prone to degradative change. Keratin, which is the primary element in hair and nail undergoes slow degradation depending on the environment it is exposed to.
– It is believed that one should be particularly careful in the disposal of hair after cutting or brushing, as such removable parts of the body can be used in witchcraft against you. Birds must also be prevented from using your hair to make their nests, as this would mean a headache, or if a magpie, death within a year, so the only safe method of disposal is to burn it.
– A belief reported from the 17th century to the present day is that if a person’s hair grows into a low point over the forehead, like a peak, she/he will be widowed soon—hence the name ‘Widow’s peak’.
-Schoolchildren had a particularly useful belief: if you place a single hair across the palm of your hand, it will split the cane with which you are being chastised, or at least it will considerably lessen the pain felt
– It is believed that if you swallow a long strand of hair, it will entwine around your heart and kill you!
– Red-haired people were considered unreliable and hot-tempered. Red-haired children were sometimes quoted as evidence of their mother’s infidelity.
Did you know: There is even a school of character reading from the hair, known as trichsomancy.
In Hindu culture, it is believed that the base of the hair shaft contains certain hormones that stimulate the opposite sex. This, combined with the notion that the woman’s hair is the most attractive part of her body, was the reason behind tonsuring (shaving) of a woman after her husband’s death, so that no person would be attracted to her and thereby secure her chastity. This is the reason why the son tonsures his head after his parents’ death, it instills a sense of detachment from worldly pleasures in him for the duration of mourning.