Elephant Hair Surprise
19 Jul 2013
Elephant hair causes cooling , not warming .
The idea that low surface densities of hairs could be a heat loss mechanism is understood in engineering and has been postulated in some thermal studies of animals. However, its biological implications, both for thermoregulation as well as for the evolution of epidermal structures, have not yet been noted. Since early epidermal structures are poorly preserved in the fossil record, we study modern elephants to infer not only the heat transfer effect of present-day sparse hair, but also its potential evolutionary origins. Here we use a combination of theoretical and empirical approaches, and a range of hair densities determined from photographs, to test whether sparse hairs increase convective heat loss from elephant skin, thus serving an intentional evolutionary purpose. Our conclusion is that elephants are covered with hair that significantly enhances their thermoregulation ability by over 5% under all scenarios considered, and by up to 23% at low wind speeds where their thermoregulation needs are greatest. The broader biological significance of this finding suggests that maintaining a low-density hair cover can be evolutionary purposeful and beneficial, which is consistent with the fact that elephants have the greatest need for heat loss of any modern terrestrial animal because of their high body-volume to skin-surface ratio. Elephant hair is the first documented example in nature where increasing heat transfer due to a low hair density covering may be a desirable effect, and therefore raises the possibility of such a covering for similarly sized animals in the past. This elephant example dispels the widely-held assumption that in modern endotherms body hair functions exclusively as an insulator and could therefore be a first step to resolving the prior paradox of why hair was able to evolve in a world much warmer than our own.
Citation: Myhrvold CL, Stone HA, Bou-Zeid E (2012) What Is the Use of Elephant Hair? PLoS ONE 7(10): e47018. doi:10.1371/journal.pone.0047018”
“ Our work is consistent with findings for leaf hairs and cactus spines , , whose sparse projections create an effect analogous to elephant hairs in both cases. It is likely that examples exist for other present-day biological organisms, particularly plants, which should be investigated in future work.”
“A new school of research, led by scientists like University of Utah biologist Dennis Bramble and Harvard University palaeoanthropologist Daniel Lieberman, suggests that early humans needed rapid cooling systems like sweat glands and now, perhaps, hair.”
3.Pin fin design
· Pin fin heat sinks are considered to be among the most powerful heat sink designs available today
· Pin fin heat sinks provide very low thermal resistance values per given space and low pressure drop
· The cooling capabilities of pin fins stem from the round geometry of the pins, the omnidirectional pin configuration, and the use of highly conductive materials
· The smooth round pins reduce resistance to incoming air streams and enhance air turbulence between the pins
· The omnidirectional structure maximizes the entrance of fresh air into the pin array and at the same time allows the hot air to exhaust from the pin array in every possible direction
· The use of highly conductive materials further reduces the thermal resistance of the heat sinks
· Cool Innovations has further enhanced the performance of pin fin heat sinks via the introduction of the splayed and flared pin fin designs
· Their unique structure allows them to offer lower thermal resistance values and lower pressure drop per given space
4.Polar bears :
In hot temperatures , there is no insulating fluff . Only erect pins . The bear is quite capable of handling high temperatures .
Feathers evolved to dump heat . But could conserve it as well .
6.Flapping of feathers by large dinosaurs in a hot environment served to cool them . The physics requires only a moderate relative windspeed .
7.The feathers would be in an erectile state in a warm environment .
8.A cold period would stimulate flight . The feathers would close in .
9.Thorns on desert plants :
Not defense , but temperature regulation .
10 .That is why thorny desert plants are not poisonous , while many tropical plants are .
Ever wondered why desert plants are succulent , but not poisonous ?
Not high enough density of herbivores to trigger high-cost formation of poisons . The spines/thorns help against predators , but they eat them anyway .
Temperature control !
Most of its body hair is found on the ear fringes and tail bristles, with the rest distributed rather sparsely over the rest of the body.
The horn is rather inferior hair .The bio-active hair are found on the body .
Rhino should be farmed and shorn like sheep in winter . The body hair contains sildanifil (Viagra) to erect them in hot weather .
Shorn ostrich feathers will have the same effect . Probably better . Older .
Ostrich feathers can be substituted for rhino horn .
12. Crocodile feathers .
A slight genetic tweak and you can have thousands of tons of compacted crocodile feathers (ie hair) , ie rhino horn .
Shearing rhino’s and crocodiles takes real men .