Human biological adaptability
The human body readily responds to changing environmental stresses in a variety of biological and cultural ways. We can acclimatize to a wide range of temperature and humidity. When traveling to high altitudes, our bodies adjust so that our cells still receive sufficient oxygen. We also are constantly responding in physiological ways to internal and external stresses such as bacterial and viral infections, air and water pollution, dietary imbalance, and overcrowding.This ability to rapidly adapt to varying environmental conditions has made it possible for us to survive in most regions of the world. We live successfully in humid tropical forests, harsh deserts, arctic wastelands, and even densely populated cities with considerable amounts of pollution. Most other animal and plant species are restricted to one or relatively few environments by their more limited adaptability.
Pongthorn Freeman
Pongthorn Freeman
Genetic Change of the body
When an environmental stress is constant and lasts for many generations, successful adaptation may develop through biological evolution. Those individuals who inherit a trait that offers an advantage in responding to particular stresses are more likely to survive longer and pass on more of their genes to the next generation. This is evolution through natural selection. For instance, people whose ancestors have lived in areas that have had endemic malaria for thousands of years often inherit some degree of immunity to this serious disease. The high incidence of sickle-cell trait among the people of Central Africa is largely the result of indirect selection for this trait by malaria. Heterozygous carriers of the sickling gene usually do not have sickle-cell anemia and are sufficiently resistant to the malarial microorganism that they are at a selective advantage. Another example of a genetic solution to an environmental stress is our ability to produce sweat as an aid in cooling our bodies in hot environments. It is not surprising that we have this capability because our immediate pre-human ancestors were tropical animals.
Genetic change in response to environmental stresses usually takes many generations to become widespread in a population. Fortunately, we also have other ways of responding more quickly as individuals during our own lifetime. The word adjustment is used here to refer to these shorter term physiological changes that are not inheritable. The word adaptation is reserved for inheritable genetic changes developed in a population over a long period of time.
Researchers identified the origins of more than 1.15 million single-nucleotide variants, that is, "locations where a single letter of the DNA sequence is different from other individuals" in the genomes of the studied sample. These changes were found in those sections of the genes that provide the template for building proteins. Besides confirming that these variations occurred during the past 5,000-10,000 years, they also found that changes reflected different routes and times of migration by humans.
Pongthorn Freeman
Genetic change in response to environmental stresses usually takes many generations to become widespread in a population. Fortunately, we also have other ways of responding more quickly as individuals during our own lifetime. The word adjustment is used here to refer to these shorter term physiological changes that are not inheritable. The word adaptation is reserved for inheritable genetic changes developed in a population over a long period of time.
Researchers identified the origins of more than 1.15 million single-nucleotide variants, that is, "locations where a single letter of the DNA sequence is different from other individuals" in the genomes of the studied sample. These changes were found in those sections of the genes that provide the template for building proteins. Besides confirming that these variations occurred during the past 5,000-10,000 years, they also found that changes reflected different routes and times of migration by humans.
Pongthorn Freeman
Genetic mutations can lead to speciation
The force of mutation is the ultimate source of new genetic variation within populations. Although most mutations are neutral with no effect on fitness or harmful, some mutations have a small, positive effect on fitness and these variants are the raw materials for gradualistic adaptive evolution. Within finite populations, random genetic drift and natural selection affect the mutational variation. Natural selection is the only evolutionary force which can produce adaptation, the fit between organism and environment, or conserve genetic states over very long periods of time in the face of the dispersive forces of mutation and drift. The force of migration or gene flow has effects on genetic variation that are the opposite of those caused by random genetic drift. Migration limits the genetic divergence of populations and so impedes the process of speciation.
http://plato.stanford.edu/entries/evolutionary-genetics/
Thulangana Ganeshan
http://plato.stanford.edu/entries/evolutionary-genetics/
Thulangana Ganeshan
Developmental Adjustment
One of the more powerful types of adjustments to environmental stresses is a change in growth patterns and development. This occurs in childhood and typically results in anatomical and/or physiological changes that are mostly irreversible in adulthood. Such permanent changes are referred to as developmental adjustment or developmental acclimatization.Among humans, developmental adjustments result from both natural environmental pressures and cultural practices. An example of the latter was the now illegal custom in China of tightly wrapping or binding the feet of young girls with cloth in order to hinder normal growth. While this caused permanent, crippling deformities of the foot bones, it also resulted in extremely tiny feet which were considered to be very attractive. Parents crippled their daughters with good intentions. Small feet would make them more attractive marriage partners for rich important men and save them from a life of drudgery.
It is easy to condemn the old Chinese custom of foot binding as being barbaric. However, it is worth considering that North Americans and Europeans haveintentionally altered parts of the bodies of their children and themselves with unpleasant procedures as well. In the late 19th century, tight corsets worn by girls when their bodies were still growing had the effect of deforming lower rib bones dangerously in towards their lungs. Some rich women even had lower ribs surgically removed in order to achieve a stylish "wasp-shaped" waist. A 19 inch circumference was the ideal.
Intentional deformation of parts of the body is not something that only happened in the past. In China today, there is a growing concern among many upwardly mobile middle class men and women that they are too short. Thousands have sought a solution to this problem by having their legs lengthened. This is achieved by a long, painful process involving the surgical breaking of the two lower leg bones in both legs and then using adjustable metal braces that are anchored with steel pins implanted in the bone just below the knees and above the ankles to progressively extend the length by nearly 1/16 inch (about 1 mm.) a day as the bones heal. This widens the gap at the break areas, thereby stimulating new bone growth. As a result, the average patient permanently adds about 3 inches (7-8 cm.) to their height in half a year.
Pongthorn Freeman
It is easy to condemn the old Chinese custom of foot binding as being barbaric. However, it is worth considering that North Americans and Europeans haveintentionally altered parts of the bodies of their children and themselves with unpleasant procedures as well. In the late 19th century, tight corsets worn by girls when their bodies were still growing had the effect of deforming lower rib bones dangerously in towards their lungs. Some rich women even had lower ribs surgically removed in order to achieve a stylish "wasp-shaped" waist. A 19 inch circumference was the ideal.
Intentional deformation of parts of the body is not something that only happened in the past. In China today, there is a growing concern among many upwardly mobile middle class men and women that they are too short. Thousands have sought a solution to this problem by having their legs lengthened. This is achieved by a long, painful process involving the surgical breaking of the two lower leg bones in both legs and then using adjustable metal braces that are anchored with steel pins implanted in the bone just below the knees and above the ankles to progressively extend the length by nearly 1/16 inch (about 1 mm.) a day as the bones heal. This widens the gap at the break areas, thereby stimulating new bone growth. As a result, the average patient permanently adds about 3 inches (7-8 cm.) to their height in half a year.
Pongthorn Freeman
the human body - adaptation
Lost in a cave tests human adaptation to the extent where there is no light and eyesight became disabled
Pongthorn Freeman
Pongthorn Freeman
Combined effect
Genetic adaptation and the three types of adjustments to environmental stresses are not always distinct phenomena. Acclimatization occurring in childhood may result in permanent anatomical changes, as is often the case with malnutrition. When an acclimatization is successful in providing good health and longevity, it can give individuals a selective advantage in passing on their genes to the next generation. This can have a strong determinant effect on the direction of evolution. In turn, genetic change can play a significant role in adjustment since the ability to acclimatize is ultimately dependent on genetic makeup.
Adaptability to specific environmental stresses varies from person to person and from population to population. We are not all biologically equal. For instance, some groups of people are more successful in adjusting to high altitudes. Others can better handle intense heat and high humidity. Adaptive responses tend to occur in spatial clusters around the world. Usually, the most efficient adaptations for specific environmental stresses are found in areas where those stresses are most common. This is evidence that natural selection has occurred in the successfully adapting population.
Pongthorn Freeman
Adaptability to specific environmental stresses varies from person to person and from population to population. We are not all biologically equal. For instance, some groups of people are more successful in adjusting to high altitudes. Others can better handle intense heat and high humidity. Adaptive responses tend to occur in spatial clusters around the world. Usually, the most efficient adaptations for specific environmental stresses are found in areas where those stresses are most common. This is evidence that natural selection has occurred in the successfully adapting population.
Pongthorn Freeman
Evolution of human adaptations
Humans face basically the same adaptive challenges as all organisms
But humans are unique in having most of their adaptations transmitted culturally
Culture has a biological basis: imitativeness, sociability, inventiveness
Cultural adaptations built up incrementally over a long time spans of time
Other social animals have simple cultural adaptations, but only humans have spectacularly complex ones.
Because of cultural adaptations, people have adapted to almost all of the earth’s terrestrial habitats.
- Expansion of NE Asian people into the Americas around 14,000 years ago.
- Polynesian expansion: the last great spread of humans to the undiscovered. remote Pacific 200 BC-1000 AD.
Some human genetic adaptations.
–Body form adapted to climate as in other animals
• Tropical people tall and lean to lose heat.
• Arctic and mountain people short and wide to conserve heat.
–Pale skin adapted to vitamin D photosynthesis in dim climates.
Many gene-culture coadaptations
-Disease resistance genes
• Malaria
• Plague
–Diet related genes
• Adult lactose absorption and dairying
• Alcohol metabolism and grains and grapes for alcoholic beverages
How does culture evolve: A Darwinian view•Random variation
•Natural selection
•Decision-making forces
(Only humans do thison a large scale)
– Individual learning + teaching and imitation
–Biased teaching
• Biased imitation
–Perceived quality of variants
–Perceived quality of person (“opinion leaders”)
–Public opinion
Pongthorn Freeman
But humans are unique in having most of their adaptations transmitted culturally
Culture has a biological basis: imitativeness, sociability, inventiveness
Cultural adaptations built up incrementally over a long time spans of time
Other social animals have simple cultural adaptations, but only humans have spectacularly complex ones.
Because of cultural adaptations, people have adapted to almost all of the earth’s terrestrial habitats.
- Expansion of NE Asian people into the Americas around 14,000 years ago.
- Polynesian expansion: the last great spread of humans to the undiscovered. remote Pacific 200 BC-1000 AD.
Some human genetic adaptations.
–Body form adapted to climate as in other animals
• Tropical people tall and lean to lose heat.
• Arctic and mountain people short and wide to conserve heat.
–Pale skin adapted to vitamin D photosynthesis in dim climates.
Many gene-culture coadaptations
-Disease resistance genes
• Malaria
• Plague
–Diet related genes
• Adult lactose absorption and dairying
• Alcohol metabolism and grains and grapes for alcoholic beverages
How does culture evolve: A Darwinian view•Random variation
•Natural selection
•Decision-making forces
(Only humans do thison a large scale)
– Individual learning + teaching and imitation
–Biased teaching
• Biased imitation
–Perceived quality of variants
–Perceived quality of person (“opinion leaders”)
–Public opinion
Pongthorn Freeman
Natural selection on culture
Today fertility in most human populations is falling and is below replacement in many areas
• Analogous to a disease
• Amish (and a few other groups) are sealed off from modern culture by their religion
• Amish have very traditional family roles
• Women gain all of their status from raising a family and so mostly do men
• Amish have natural fertility (average ~ 7 kids per family
• Amish population is growing very rapidly
• Analogous to a disease
• Amish (and a few other groups) are sealed off from modern culture by their religion
• Amish have very traditional family roles
• Women gain all of their status from raising a family and so mostly do men
• Amish have natural fertility (average ~ 7 kids per family
• Amish population is growing very rapidly
Role of history
• Humans may have been in ~ equilibrium with the prevailing environment from 40,000 BP to 15,000 BP in Eurasia
• No detectable progress after moderns replaced Neanderthals until the ice began to melt
• Dale Guthrie i a recent book argues that the cave art of the ice was very strange: very naturalistic, no supernatural images, no war
• Since the ice, humans have evolved toward greater social and technical complexity, albeit at different rates in different places
Pongthorn Freeman
• No detectable progress after moderns replaced Neanderthals until the ice began to melt
• Dale Guthrie i a recent book argues that the cave art of the ice was very strange: very naturalistic, no supernatural images, no war
• Since the ice, humans have evolved toward greater social and technical complexity, albeit at different rates in different places
Pongthorn Freeman
Sources
Online Sources / Websites
Human Biological Adaptability: Overview. [ONLINE]
Available at: http://anthro.palomar.edu/adapt/adapt_1.htm.
Most genetic changes in humans occurred in past 5000 years, finds new study - The Times of India. [ONLINE]
Available at: http://timesofindia.indiatimes.com/home/science/Most-genetic-changes-in-humans-occurred-in-past-5000-years-finds-new-study/articleshow/17414195.cms.
Challenges in human genetic diversity: demographic history and adaptation . [ONLINE]
Available at: http://hmg.oxfordjournals.org/content/16/R2/R134.full.
The genetics of human adaptation: hard sweeps, sof... [Curr Biol. 2010] - PubMed - NCBI. [ONLINE]
Available at: http://www.ncbi.nlm.nih.gov/pubmed/20178769.
The Human Body - Adaptation: Lost In A Cave - YouTube. [ONLINE]
Available at: http://www.youtube.com/watch?v=1LS9sHwz1Wk.
Human Adaptation Lecture. 2014. . [ONLINE]
Available at: http://www.des.ucdavis.edu/faculty/Richerson/ESP30/0-4%20Human%20Adaptations.pdf.
On natural selection - YouTube. 2014. On natural selection - YouTube. [ONLINE]
Available at: http://www.youtube.com/watch?v=dgKSHFL3Vd8.
Future Human | Future Human and the V&A launch Visionaries podcast. [ONLINE]
Available at: http://www.futurehuman.co.uk/.
Petrov.stanford.edu. 2014. ::: The Petrov Lab :::. [ONLINE]
Available at: http://petrov.stanford.edu/
Books / PDFs
Endler, J. A.Natural selection in the wildIn-text: (Endler, 1986) [BOOK]
Bibliography: Endler, J. A. 1986. Natural selection in the wild. Princeton, N.J.: Princeton University Press.
Williams, G. C.Adaptation and natural selectionIn-text: (Williams, 1996)[BOOK]
Bibliography: Williams, G. C. 1996. Adaptation and natural selection. Princeton, N.J.: Princeton University Press.
The role of phenotypic plasticity in driving genetic evolution, [PDF]
By Trevor D. Price1*, Anna Qvarnstro¨m2 and Darren E. Irwin3
Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691402/pdf/12965006.pdf
The Role Of Mutation, inbreeding, Crossbreeding and selection in evolution.[PDF]
By Sewall Wright, University of Chicago
Available at http://www.esp.org/books/6th-congress/facsimile/contents/6th-cong-p356-wright.pdf
Researches by Pongthorn Freeman
Online Sources / Websites
Human Biological Adaptability: Overview. [ONLINE]
Available at: http://anthro.palomar.edu/adapt/adapt_1.htm.
Most genetic changes in humans occurred in past 5000 years, finds new study - The Times of India. [ONLINE]
Available at: http://timesofindia.indiatimes.com/home/science/Most-genetic-changes-in-humans-occurred-in-past-5000-years-finds-new-study/articleshow/17414195.cms.
Challenges in human genetic diversity: demographic history and adaptation . [ONLINE]
Available at: http://hmg.oxfordjournals.org/content/16/R2/R134.full.
The genetics of human adaptation: hard sweeps, sof... [Curr Biol. 2010] - PubMed - NCBI. [ONLINE]
Available at: http://www.ncbi.nlm.nih.gov/pubmed/20178769.
The Human Body - Adaptation: Lost In A Cave - YouTube. [ONLINE]
Available at: http://www.youtube.com/watch?v=1LS9sHwz1Wk.
Human Adaptation Lecture. 2014. . [ONLINE]
Available at: http://www.des.ucdavis.edu/faculty/Richerson/ESP30/0-4%20Human%20Adaptations.pdf.
On natural selection - YouTube. 2014. On natural selection - YouTube. [ONLINE]
Available at: http://www.youtube.com/watch?v=dgKSHFL3Vd8.
Future Human | Future Human and the V&A launch Visionaries podcast. [ONLINE]
Available at: http://www.futurehuman.co.uk/.
Petrov.stanford.edu. 2014. ::: The Petrov Lab :::. [ONLINE]
Available at: http://petrov.stanford.edu/
Books / PDFs
Endler, J. A.Natural selection in the wildIn-text: (Endler, 1986) [BOOK]
Bibliography: Endler, J. A. 1986. Natural selection in the wild. Princeton, N.J.: Princeton University Press.
Williams, G. C.Adaptation and natural selectionIn-text: (Williams, 1996)[BOOK]
Bibliography: Williams, G. C. 1996. Adaptation and natural selection. Princeton, N.J.: Princeton University Press.
The role of phenotypic plasticity in driving genetic evolution, [PDF]
By Trevor D. Price1*, Anna Qvarnstro¨m2 and Darren E. Irwin3
Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691402/pdf/12965006.pdf
The Role Of Mutation, inbreeding, Crossbreeding and selection in evolution.[PDF]
By Sewall Wright, University of Chicago
Available at http://www.esp.org/books/6th-congress/facsimile/contents/6th-cong-p356-wright.pdf
Researches by Pongthorn Freeman
Skin Pigmentation
Light is an essential source in life, however without the exposure of light the surrounding environment becomes colder and remains dark. How are humans capable of surviving and adapting themselves to these conditions?
We believe skin pigmentation can result firstly as it is prone to change without sunlight exposure. The skin colour would become paler and prone to develop albinism.
Skin color is due primarily to the presence of a pigment called melanin , which is controlled by at least 6 genes. Both light and dark complexioned people have melanin. However, two forms are produced--pheomelanin , which is red to yellow in color, and eumelanin , which is dark brown to black. People with light complexioned skin mostly produce pheomelanin, while those with dark colored skin mostly produce eumelanin. In addition, individuals differ in the number and size of melanin particles. The latter two variables are more important in determining skin color than the percentages of the different kinds of melanin. In lighter skin, color is also affected by red cells in blood flowing close to the skin. To a lesser extent, the color is affected by the presence of fat under the skin and carotene , a reddish-orange pigment in the skin. Hair color is also due to the presence of melanin. Melanin is normally located in the epidermis , or outer skin layer. It is produced at the base of the epidermis by specialized cells called melanocytes . These cells have photosensitive receptors, similar to those in the eye, that detect ultraviolet radiation from the sun and other sources. In response, they produce melanin within a few hours of exposure.
Nature has selected for people with darker skin in tropical latitudes, especially in no forested regions, where ultraviolet radiation from the sun is usually the most intense. Melanin acts as a protective biological shield against ultraviolet radiation. By doing this, it helps to prevent sunburn damage that could result in DNA changes and, subsequently, several kinds of malignant skin cancers. Melanoma in particular is a serious threat to life. People who live in far northern latitudes, where solar radiation is relatively weak most of the year, have an advantage if their skin has little shielding pigmentation. Nature selects for less melanin when ultraviolet radiation is weak. The Inuit people of the American Subarctic are an exception. They have moderately heavy skin pigmentation despite the far northern latitude at which they live. While this is a disadvantage for vitamin D production, they apparently made up for it by eating fish and sea mammal blubber that are high in vitamin D. In addition, the Inuit have been in the far north for only about 5,000 years. This may not have been enough time for significantly lower melanin production to have been selected for by nature.
http://anthro.palomar.edu/adapt/adapt_4.htm
Thulangana ganeshan
ADAPTATIONS TO THE COLD SURROUNDINGS WITH NO LIGHT
Humans may have to adapt to the cold surroundings. Thereby, the metabolic regulation of the body can be affected, the volume of body fluids and blood flow can change and also homeostasis can be affected. Body insulation prevents heat loss. Deposition of fat under the skin and increase in body hair growth retains body heat, thereby adapting to the change in the colder environment.
Low temperatures also reduce the efficiency of pain receptors. Exposure to cold causes a reduction in blood flow to the surface of the skin by constriction of blood vessels. This reduces the overall volume of the circulatory system so increasing the blood pressure. The body's response to this is to reduce the fluid volume by getting rid of water in the urine. Muscular contraction is an inefficient process and causes much heat to be produced, so when we start to feel cold, we may begin to shiver, movements that are useless in themselves, but that generate heat as a by-product and so help to warm us up. Shivering can increase the production of heat five-fold.
http://www.coolantarctica.com/Antarctica%20fact%20file/science/cold_humans.htm
Thulangana Ganeshan
SLEEP CYCLE VARIATIONS
How far does the sleep cycle get affected without exposure to light? Determining day or night depends on the sun exposure, but however, without the sun, artificial energy sources could be used to mimic these effects to regulate the sleep cycle routine.
“When we consider the relationships between sunlight, survival and resilience, we usually think about how light makes vision possible and how our ability to perceive the environment is critical to our survival. While vision assists us in knowing what is in our immediate surroundings, many other sunlight sensing mechanisms have evolved to help us predict changes in the environment, especially changes that used to impact food availability and long-term survival like seasonal changes in duration of day and night.
A closer look at non-visual sunlight detecting mechanisms (ie photoperiodism) demonstrates that human physiology has evolved to optimize resilience and vitality through processes that are sensitive to the timing and the spectral distribution of sunlight.
One of the best understood examples of non-visual sunlight sensing is demonstrated by retinal cells that relay light information to the part of the brain, called the suprachiasmic nucleus (SCN), that controls melatonin secretion and the the sleep-wake cycle. Light, especially from the blue part of the spectrum, increases brain activity associated with alertness. Darkness increases melatonin secretion which is associated with sleep.
In humans, light exposure at night suppresses melatonin secretion which delays or disrupts sleep depending on the timing and color spectra of the the light. From an evolutionary and adaptive perspective, using sunlight to regulate the wake-sleep cycle synchronized alertness, activity and sleep with the long days and short nights of summer.” By better understanding our bodies’ natural rhythms and their relationship to natural cycles of light and dark, we can make more health-promoting and health-sustaining decisions. We can use what we know about our natural, biological rhythms to improve our sleep, bolster our mood, regulate our metabolism and reduce our risk for chronic diseases.
“The amount and intensity of light required to get the SCN to send “awake” signals to the body is about 500 billion photons per second per square centimeter of blue wavelength light — equivalent to the amount and type of light that reaches the eye at sunrise. But much of the artificial light we use today, including high-intensity discharge lamps (often used in streetlights) and fluorescent lamps (in offices everywhere), also contain blue wavelength light. This tricks our SCN into thinking it’s perpetually sunrise — and, hence, that it’s always time to be awake and alert. Conversely, if we are not exposed to enough blue wavelength light, we don’t get the proper wake-up cue.”
http://auraviva.com/circadian-rhythms/article/section/survival-and-vitality-through-adaptation
http://experiencelife.com/article/light-rhythms/
We believe skin pigmentation can result firstly as it is prone to change without sunlight exposure. The skin colour would become paler and prone to develop albinism.
Skin color is due primarily to the presence of a pigment called melanin , which is controlled by at least 6 genes. Both light and dark complexioned people have melanin. However, two forms are produced--pheomelanin , which is red to yellow in color, and eumelanin , which is dark brown to black. People with light complexioned skin mostly produce pheomelanin, while those with dark colored skin mostly produce eumelanin. In addition, individuals differ in the number and size of melanin particles. The latter two variables are more important in determining skin color than the percentages of the different kinds of melanin. In lighter skin, color is also affected by red cells in blood flowing close to the skin. To a lesser extent, the color is affected by the presence of fat under the skin and carotene , a reddish-orange pigment in the skin. Hair color is also due to the presence of melanin. Melanin is normally located in the epidermis , or outer skin layer. It is produced at the base of the epidermis by specialized cells called melanocytes . These cells have photosensitive receptors, similar to those in the eye, that detect ultraviolet radiation from the sun and other sources. In response, they produce melanin within a few hours of exposure.
Nature has selected for people with darker skin in tropical latitudes, especially in no forested regions, where ultraviolet radiation from the sun is usually the most intense. Melanin acts as a protective biological shield against ultraviolet radiation. By doing this, it helps to prevent sunburn damage that could result in DNA changes and, subsequently, several kinds of malignant skin cancers. Melanoma in particular is a serious threat to life. People who live in far northern latitudes, where solar radiation is relatively weak most of the year, have an advantage if their skin has little shielding pigmentation. Nature selects for less melanin when ultraviolet radiation is weak. The Inuit people of the American Subarctic are an exception. They have moderately heavy skin pigmentation despite the far northern latitude at which they live. While this is a disadvantage for vitamin D production, they apparently made up for it by eating fish and sea mammal blubber that are high in vitamin D. In addition, the Inuit have been in the far north for only about 5,000 years. This may not have been enough time for significantly lower melanin production to have been selected for by nature.
http://anthro.palomar.edu/adapt/adapt_4.htm
Thulangana ganeshan
ADAPTATIONS TO THE COLD SURROUNDINGS WITH NO LIGHT
Humans may have to adapt to the cold surroundings. Thereby, the metabolic regulation of the body can be affected, the volume of body fluids and blood flow can change and also homeostasis can be affected. Body insulation prevents heat loss. Deposition of fat under the skin and increase in body hair growth retains body heat, thereby adapting to the change in the colder environment.
Low temperatures also reduce the efficiency of pain receptors. Exposure to cold causes a reduction in blood flow to the surface of the skin by constriction of blood vessels. This reduces the overall volume of the circulatory system so increasing the blood pressure. The body's response to this is to reduce the fluid volume by getting rid of water in the urine. Muscular contraction is an inefficient process and causes much heat to be produced, so when we start to feel cold, we may begin to shiver, movements that are useless in themselves, but that generate heat as a by-product and so help to warm us up. Shivering can increase the production of heat five-fold.
http://www.coolantarctica.com/Antarctica%20fact%20file/science/cold_humans.htm
Thulangana Ganeshan
SLEEP CYCLE VARIATIONS
How far does the sleep cycle get affected without exposure to light? Determining day or night depends on the sun exposure, but however, without the sun, artificial energy sources could be used to mimic these effects to regulate the sleep cycle routine.
“When we consider the relationships between sunlight, survival and resilience, we usually think about how light makes vision possible and how our ability to perceive the environment is critical to our survival. While vision assists us in knowing what is in our immediate surroundings, many other sunlight sensing mechanisms have evolved to help us predict changes in the environment, especially changes that used to impact food availability and long-term survival like seasonal changes in duration of day and night.
A closer look at non-visual sunlight detecting mechanisms (ie photoperiodism) demonstrates that human physiology has evolved to optimize resilience and vitality through processes that are sensitive to the timing and the spectral distribution of sunlight.
One of the best understood examples of non-visual sunlight sensing is demonstrated by retinal cells that relay light information to the part of the brain, called the suprachiasmic nucleus (SCN), that controls melatonin secretion and the the sleep-wake cycle. Light, especially from the blue part of the spectrum, increases brain activity associated with alertness. Darkness increases melatonin secretion which is associated with sleep.
In humans, light exposure at night suppresses melatonin secretion which delays or disrupts sleep depending on the timing and color spectra of the the light. From an evolutionary and adaptive perspective, using sunlight to regulate the wake-sleep cycle synchronized alertness, activity and sleep with the long days and short nights of summer.” By better understanding our bodies’ natural rhythms and their relationship to natural cycles of light and dark, we can make more health-promoting and health-sustaining decisions. We can use what we know about our natural, biological rhythms to improve our sleep, bolster our mood, regulate our metabolism and reduce our risk for chronic diseases.
“The amount and intensity of light required to get the SCN to send “awake” signals to the body is about 500 billion photons per second per square centimeter of blue wavelength light — equivalent to the amount and type of light that reaches the eye at sunrise. But much of the artificial light we use today, including high-intensity discharge lamps (often used in streetlights) and fluorescent lamps (in offices everywhere), also contain blue wavelength light. This tricks our SCN into thinking it’s perpetually sunrise — and, hence, that it’s always time to be awake and alert. Conversely, if we are not exposed to enough blue wavelength light, we don’t get the proper wake-up cue.”
http://auraviva.com/circadian-rhythms/article/section/survival-and-vitality-through-adaptation
http://experiencelife.com/article/light-rhythms/
Thulangana Ganeshan
What Will 'Future Humans' Eat?
There has been much discussion and speculation as to what these 'future humans' will eat as in any event there is likely to be very little food. As we are basing our no light future on a similar event (if not the same event) of how the dinosaurs become extinct, I looked into what happened to their eating habits when the vegetation died off. Once the vegetation died out, the first dinosaurs to die would be the herbivores, when this disaster stuck the things that dinosaurs are famous for became their biggest vulnerability, the bigger the dinosaur was the quicker the species died out, leaving plenty of pickings for the carnivores.
When these become scarce competition for corpses between carnivores increase, as the dinosaurs become so desperate and hunger takes over the first signs of cannibalism become evident. The video below shows that the most successful killers will exploit any situation to their maximum advantage.
From this research it shows that potentially this could happen to these 'Future humans' however it doesn't necessarily mean that humans will follow the footsteps of the dinosaurs. After all if every living creature become extinct when the dinosaurs died out there wouldn't be life on earth today.
- Holly
There has been much discussion and speculation as to what these 'future humans' will eat as in any event there is likely to be very little food. As we are basing our no light future on a similar event (if not the same event) of how the dinosaurs become extinct, I looked into what happened to their eating habits when the vegetation died off. Once the vegetation died out, the first dinosaurs to die would be the herbivores, when this disaster stuck the things that dinosaurs are famous for became their biggest vulnerability, the bigger the dinosaur was the quicker the species died out, leaving plenty of pickings for the carnivores.
When these become scarce competition for corpses between carnivores increase, as the dinosaurs become so desperate and hunger takes over the first signs of cannibalism become evident. The video below shows that the most successful killers will exploit any situation to their maximum advantage.
From this research it shows that potentially this could happen to these 'Future humans' however it doesn't necessarily mean that humans will follow the footsteps of the dinosaurs. After all if every living creature become extinct when the dinosaurs died out there wouldn't be life on earth today.
- Holly
Skin Cancer Prevention
Skin cancer is caused by long term exposure to the sun. Sunlight contains UV radiation that can damage the genes and the DNA in the skin cells. There are usually two types of skin cancer:
Basal skin cancer and
Squamous skin cancer.
People with high exposure to UV light are at a greater risk of developing skin cancer. People living in places with exposure to bright sunlight are more prone to develop the risk of skin cancer. Other risk factors such as skin color (The risk of skin cancer is much higher for whites than for dark-skinned African Americans or Hispanics. This is because melanin helps protect against UV radiation. People with dark skin have more melanin. People with fair (light-colored) skin that freckles or burns easily are at extra high risk), older age, chemical exposure, radiations, genetics and other skin problems can contribute to developing skin cancer.
Therefore for future humans, without the exposure of sunlight this could be an advantage for them. There is the possibility of preventing skin cancer in this kind of
species.
http://www.skincancerprevention.org/skin-cancer/risk-factors
Thulangana Ganeshan
Basal skin cancer and
Squamous skin cancer.
People with high exposure to UV light are at a greater risk of developing skin cancer. People living in places with exposure to bright sunlight are more prone to develop the risk of skin cancer. Other risk factors such as skin color (The risk of skin cancer is much higher for whites than for dark-skinned African Americans or Hispanics. This is because melanin helps protect against UV radiation. People with dark skin have more melanin. People with fair (light-colored) skin that freckles or burns easily are at extra high risk), older age, chemical exposure, radiations, genetics and other skin problems can contribute to developing skin cancer.
Therefore for future humans, without the exposure of sunlight this could be an advantage for them. There is the possibility of preventing skin cancer in this kind of
species.
http://www.skincancerprevention.org/skin-cancer/risk-factors
Thulangana Ganeshan