physical adaptation

7/29/2019 Physical Adaptation

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PHYSICAL ADAPTATION

Adaptations are often specific to a particular environment. What is adaptive to oneenvironment may not be in another. Secondly we must keep in mind that not all aspects

of behaviour or biology are adaptive. Some people have earlobes attached to the skin of

their skulls, whereas others have earlobes that hang free. There is no adaptivesignificance to either trait.

Anthropology is concerned with determining what humans are, how they evolved andhow they differ from one another. Where other scientific disciplines focus on specific

issues of humanity, anthropology is unique in dealing simultaneously with questions of

origins, evolution, variation and apaptation.

Adaptation is the successful interaction of a population with its environment. Central to

the study of adaptation is the concept ofSTRESS or to define it broadly, any factor that

interferes with the normal limits of operation of an organism.

Organisms maintain these limits through HOMEOSTASIS. As ways of dealing with the

stresses that your bodys functioning, adaptations restore homeostasis. For example yourbody will maintain a relatively constant body temperature however when you stand

outside on a cold autumn/winters evening you will shiver. This is the bodys way of

coping with cold stress and you may choose to put on a heavy coat.

Human beings can adapt both biologically and culturally. It is worth noting that our

biocultural nature can work against us. By adapting to stresses culturally, we may

introduce other stresses as a result of our behaviour. Key to the interaction betweenhuman biology and culture, human adaptation operates on a number of levels:

physiologic, developmental, genetic and cultural all of which are unrelated. Counteringa biological stress such as disease by the cultural adaptation of medicine can lower thedeath rate for human populations but can also increase population size which in turn can

lead to further stresses such as food shortages and environmental degradation.

As well as generic and cultural adaptation, humans are capable of three other forms of

adaptation that are physiologic in nature: ACCLIMATION refers to short term changes

that occur very quickly after exposure to stress such as sweating when you are hot.

ACCLIMATIZATION refers to physiologic changes that take longer, from days tomonths such as an increase in red blood cell production after moving to a high altitude

environment.

ACCLIMATION short term physiologic responses to a stress, usually

within minutes or hours

ACCLIMATIZATION long term physiologic responses to a stress, usually

Taking from days to months


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PLASTICITY the ability of an organism to respond physiologically or

Developmentally to environmental stress

Tanning is a form of adaptation to ultraviolet radiation from the sun. There is strong

evidence to show that in equatorial regions dark skin evolved in response to the stress of

excessive levels of ultraviolet radiation. Individuals with darker skin were more likely tosurvive and therefore more likely to pass on the genes for darker skin to the next

generation. In other words natural selection produced a genetic adaptation.

Cultural adaptations can deal with exposure to ultraviolet radiation. If you work or enjoy

leisure activities outside, this will increase your risk of exposure to ultraviolet radiation;

you can wear protective clothing and apply sunscreen. Changes in working hours as well

as play outdoors will also minimize exposure. Due to the growing concern in countriessuch as the USA and Australia amongst others in the Western world, a number of people

are turning to behaviours that provide protection from ultraviolet radiation or minimize

exposure.

Though originally tropical primates, we humans have managed to expand into virtually

every environment on our planet. Such expansion has been possible largely because ofmultiply adaptations to the range of temperatures around the world.

When you are cold, your body loses heat rapidly. One response is to increase heatproduction temporarily through shivering which increases your metabolic rate. The

response is not very efficient and is costly in terms of energy. A more efficient

physiologic response to cold stress is minimization of heat loss through alternate

constriction and dilation of blood vessels. VASOCONSTRICTION, the narrowing ofblood vessels, reduces blood flow and heat loss. VASODILATION, the opening of the

blood vessels, serves to increase blood flow and heat loss.

LEWIS HUNTING PHENOMENON - PRACTICAL CLASS

Initial exposure of a finger into iced water produces a decrease in skin temperature

caused by VASOCONSTRICTION. After a while this response gives way to

VASODILATION which causes skin temperature to increase. The cycle continues over

time but becomes more frequent and less extreme, thus providing more efficient

adaptation.

BERGMANNS RULE Among mammals of similar shape, the larger mammal

loses heat less rapidly than the smaller mammal and that among mammals of

similar size, the mammal with a linear shape will lose heat more rapidly than the

mammal with a nonlinear shape.

ALLENS RULE States that mammals in cold climates tend to have short,

bulky limbs, allowing less loss of body heat, whereas mammals in hot climates tend

to have long, slender limbs, allowing greater loss of body heat (think of African

Masai warriors)


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An example of Allen & Bermann rules is when looking at an Inuit (Eskimo) and the

Masai tribesman. The Eskimo tends to be shorter and bulkier whereas the Masai is long,

thin and slender.

Evidence to date suggests that both genetic and environmental factors influence the

relationship among climate, growth, body size and body shape. When children grow upin a climate different from that of their ancestors, they tend to grow in ways the

indigenous children do.

HYPOXIA Oxygen starvation which frequently occurs at high altitudes.

If someone hasnt eaten regularly and their intake of calories, proteins, fatty acid,

vitamins and minerals for example someone suffering Anorexia Nervosa, Bulimia,disease or illness, will usually end up with medical problems, fainting regularly can be

one such symptom.

Malnutrition / lack of food amongst cultures and societies around the world leads to poornutrition which in turn leads to smaller body sizes due to the lack of a balanced diet and

nutrition slowing the growth process. In one sense this change in growth is adaptivebecause a smaller adult body size will require fewer nutrients, thereby generating a form

of evolutionary process amongst the peoples.

http://anthro.palomar.edu/adapt/default.htm

Human Biological Adaptability, a tutorial including information on climatic, high altitude

and nutritional adaptation.

http://www.princeton.edu/~oa/safety/altitude.html

Outdoor Action Guide to high altitude, which provides information on high altitiude

illness and acclimatization.

Adaptation notes taken from Relethford, J.H. The Human Species : An

introduction to biological anthropology 5th Edition 2003. McGraw-Hill Higher

Education
http://anthro.palomar.edu/adapt/default.htmhttp://www.princeton.edu/~oa/safety/altitude.htmlhttp://anthro.palomar.edu/adapt/default.htmhttp://www.princeton.edu/~oa/safety/altitude.html


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IS FAINTING AN ADAPTATION

Adaptation is a change in a system or species in response to changes in its context or

environment so as to make that system or species more fit to survive in the context orenvironment.

To understand fainting, Vasogal Syncope (sin-ko-pea) would require a knowledge of

pathophysiology. Human physiology represents one of a vast array of evolutionary

solutions to similar problems and the question of whether such fainting mechanisms also

operate on animals would require the reader would require a knowledge of animalphysiology which could help us understand the mechanisms of human fainting.

There are three major syncope (fainting) types; cardiac which occurs in both animals and

humans: orthostatic fainting where blood pressure falls suddenly when a person suddenlystands upright and Reflex (Vasovagal) syncope or emotional fainting when feeling fear or

catching sight of blood or a traumatic incident. Emotional fainting is considered to be asurvival strategy of an attentive brain rather than fainting due to a circulatory breakdown

and is thought to be unique to humans.

Mans upright posture has been blamed for orthostatic fainting due to there being

insufficient cerebral circulation in the context of a temporary failure of the systematic

circulation. This point can be argued when comparison is made to animals. Tree

climbing snakes, giraffes and other animals that quickly raise and lower their heads,gazelles, zebras, dogs, cats in fact any animal that is feeding or drinking, especially in the

wild face more serious gravitational circulatory challenges than human beings and yet do

not appear to faint.

Another theory for human fainting, apart from cardiac which is a medical issue, is that

humans carrying their brain above the heart could be that cause of fainting due to theheart to brain height being smaller than that of many mammals with similar blood

pressure.

Two evolutionary novelties/traits may be to blame. The proportion of cardiac outputgoing upwards to the brain of primates and animals, for example apes and grizzly bears is

larger but mans large legs could suggest that the volume lost to venous pooling is longer.

Could vasovagal syncope be an evolutionary adaptation of survival that has been part of

the evolution process? During a fainting episode, the heart rate drops or can even stop

for a few seconds (bradycardia) and blood pressure drops sharply (hypotension) and suchevents could signpost up to the evolution of genetical makeup being adapted through

evolution in the likelihood of fear or stress.


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Hypotension - Drop in blood pressure due to changing body position to a more vertical

position after lying or sitting. (think evolution and primates beginning to stand on 2 feet

as opposed to sitting or walking on 4 limbs)

Dehydration - causing a decrease in blood volume (climate change)

Blood pressure medications leading to low blood pressure (not adaptive as it is societal)

Diseases - of the nerves to legs in older people predominantly those suffering with

diabetes or Parkinsons) when poor tone of the nerves of the leg draws blood into the legsfrom the brain

High Altitude - in the event of a natural disaster people may have to climb to higheraltitude for survival

physical adaptation

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