Human Variation and Race

1. Select only ONE of the following environmental stresses: (a) heat, (b) high levels of solar radiation, (c) cold, or (d) high altitude. Discuss specifically how this environmental stress negatively impacts the survival of humans by disturbing homeostasis.

High levels of solar radiation is an environmental stressor which negatively impacts the survival of humans by disturbing homeoastasis.  UVA radiation has the ability to penetrate through the epidermis all the way to the dermis layer, while UVB radiation penetrates only to the epidermis layer.  The only benefit from exposure to UV radiation is the stimulation of vitamin D production by UVB waves.  When we are sunburned, UVB and UVA rays cause short-term suppression of the immune system.  Overexposure to UVB radiation, which is directly absorbed by the DNA within cells, can potentially cause genetic damage leading to skin cancer, it is the more harmful of the two types of UV radiation.  This damage at the genetic level disturbs homeostasis and is life threatening to the species.

2. Identify 4 ways in which humans have adapted to this stress, choosing one specific adaptation from each of the different types of adaptations listed above

Short Term

A short term adaptation to overexposure from UVB/UVA rays is a sunburn.  A sunburn let’s us know that we have been in the sun too long and that further exposure will be harmful to the skin and to the DNA in our cells.  Fair skin is more apt to sunburn than darker skin as darker skin already contains a higher concentration of melanin which protects us from the UV solar radiation.  Light skinned people do not produce as much melanin, so therefore they will get a sunburn faster than dark skinned people.

Facultative

A facultative adaptation to protect us from the harmful UVB radiation waves is skin tanning.  Tanning happens when exposure to sunlight triggers a protective mechanism through increased melanin production in the epidermis layer.  Melanin is a natural sunscreen produced by our bodies and the tanning response will remain until the overexposure to UV rays is reduced.  As we spend more time in the sun during the summer months with the warmer weather, it is common to see people of both fair and dark skin have a darker complexion and then to have their complexion return to normal during winter months. 

Albinos are the only human beings who carry a genetic mutation preventing their bodies from producing melanin.  Many people of northern European descent with very fair skin, blue eyes and light hair produce very small amounts of melanin.  Without the ability to tan, their skin alone will not protect them from UV radiation. 

Developmental

A developmental change is found in populations which have a higher concentration of people with darker skin.  Dark skin contains higher concentrations of melanin, which is a natural sunscreen protection for the skin.  Populations with the most exposure to the sun’s harmful rays are located in Savannah’s and plains (mostly in African and Tropical climates).  Therefore we can see a direct correlation geographically in those regions having a higher density of people with darker skin.  Even people with darker skin can tan and sunburn.  This is because a certain amount of UV radiation is necessary for the production of Vitamin D in the body.  Too much exposure to solar radiation results in skin cancer, but too little exposure can result in a Vitamin D deficiency which can affect the body’s ability to process calcium and weaken the bones.  Populations without enough sunlight can develop diseases such as rickets, where the bones are not strong enough to support the weight of the body as it grows.  So, lighter skinned populations do not produce as much melanin because the l

esser amount of sunlight they receive is needed to obtain enough Vitamin D to prevent other diseases. 

Cultural

A cultural adaptation to the harmful UVA and UVB rays is advent of clothing, shelter and in modern history, sunscreen lotions.  Shelter and clothing made it possible for our ancestors to limit their exposure to the sun’s radiation and therefore reduced the need for such high levels of melanin production.  Migrating to other environments such as forested areas also reduced our ancestor’s time in the sun.  Over time, we can see the change in skin pigmentation with the lighter skinned populations possessing more of the northern geographical regions and darker skinned populations possessing more central and southern regions closest to the equator.  Today people of all skin pigments now populate all regions of the globe.  Outdoor sporting activities have also increased our time in the sun.  But, rather than migrate northward if you are light skinned, the invention of sunscreen lotion can protect you for longer periods of time in the sun.  However, it is not a solution that completely prevents skin cancer for either light or dark skinned people.  Too much time in the sun increases our risk of skin cancer, no matter the

color of our skin.

3. What are the benefits of studying human variation from this perspective across environmental clines? Can information from explorations like this be useful to help us in any way? Offer one example of how this information can be used in a productive way.

The benefits of studying human variation in this manner is that by studying the changes of various sample populations over time, we can evaluate and see the environmental stressors, which can affect any population.  If we took one population with one group of traits and moved them to another environment than the one in which they were born, eventually, we would see an evolutionary adaptation to the new environment.  For example, studying the high rate of sickle cell anemia in black populations can help scientists to identify and come up with treatments and hopefully cures that will help other people with sickle cell anemia, not just one population.  Studying rickets in fair skinned populations can help us understand the need for sunlight and how much sunlight is necessary to avoid the disease.

4. How would you use race to understand the variation of the adaptations you listed in #2? Explain why the study of environmental influences on adaptations is a better way to understand human variation than by the use of race. 

I would use race only to classify geographic groups of people who have the same or similar set of adaptations to the same environment.  In this way, we can see how our ancestors developed and changed over millions of years and understand our origins more fully.  It also can help us to predict what changes might occur in the human population given certain environmental stressors.

When studying the environmental influences of a group of people over long periods of time, we will begin to see patterns which evolved as adaptations to those outside stressors.  Some adaptations (such as being born with lighter or darker skin) become permanent, while others will remain until the stressor has been removed (such as tanning during the summer with increased sun exposure).  This ability to adapt and change is inherent in the entire human race and therefore connects us more closely at a genetic level than any of the outward differences we may see.  It helps us to see that our differences are simply responses to our environment and not that we are completely different species from one another, evolved from completely different ancestors.  I feel that being able to study the human species in this manner is a great tool to helping people overcome racism and see more of the ways we are alike than the ways in which we differ.

Language Experiment

Part I:  No spoken language allowed

I did my communication experiment with my 14 year old daughter.  We set a timer for 15 minutes for each round, Part 1, no speech allowed and Part 2, no gestures of any kind allowed.  Trying to communicate without words was very difficult.  Only the simplest of concepts could be explained.  Yes and no questions were easy, or letting her know she had guessed correctly.  But I was trying to communicate the idea that a woman who had sent me a letter was someone I needed to contact.  My daughter thought that I was talking about someone else and there were actually 3 different people that had to do with this particular communication.  So, it was very difficult to try and describe the identities of 3 different people to her.  

My daughter was very frustrated and telling me that I was not a very good communicator and that I was the one who had to find a different way to communicate with her.  Although we were both laughing at my attempts to communicate complex ideas, if this were a serious conversation, she was really starting to look at me and treat me as if I were not intelligent at all.

If we were from two different cultures, my daughter being able to use spoken language definitely had the advantage in communicating.  While I understood what she needed simply with her words, my gesturing could only be understood for very simple ideas.  Her attitudes towards me did begin to change the longer time went on.  She was beginning to dismiss me and really wanted to disengage in conversation at all.  I found myself getting very frustrated knowing the idea I was trying to communicate, but having limited means to express myself.  While written language would bridge the gap, unless both of these cultures had the same written language, the same frustrations would persist.  This made me feel that if I were part of the deaf community trying to communicate with the non-deaf community, it would be a very frustrating existence trying to communicate.  The fact that the deaf have created sign language is an amazing accomplishment in being able to communicate complex ideas without being able to hear speech. Yet, still, not all of us know sign language and therefore do not communicate with the deaf community.  So there is a large part of our culture most of us simply choose not to be able to speak with, myself included.  I even have partially deaf friends who are involved heavily in that community, but it has never crossed my mind to learn any of that language.

Part II: No gestures of any kind allowed

Again using my daughter to communicate with, we switched the timer to continue the experiment for another 15 minutes.  We were sure to read the rules and my daughter took great delight in letting me know if I unconsciously made any eyebrow movements with my speech.  I had my hands in my pockets, but noticed how difficult it was to separate completely spoken language from any facial gestures of any kind. 

There was considerably less frustration in regards to being able to communicate complex ideas when I was able to speak.  But my daughter found the lack of gesturing to be very strange and without vocal inflection, I had to communicate things like, whether I was joking, or upset or happy by stating those emotions rather than being able to read my body language.

I found that the “signs” or non-verbal parts of our communication are just as important in communicating the right ideas more efficiently.  It took far longer for me to communicate when I also had to explain my emotions with words rather than just being able to use my vocal inflection or facial expressions to communicate those things.

I have a son who is autistic and while he is very high functioning and is graduating from high school this week, it has been a life-long struggle for him in terms of communication.  When he was young, he did not naturally read things such as personal space, facial expressions, etc. as part of language.  I had to physically show him what the appropriate distance was to stand when having a conversation with another person.  Also, if I was angry and telling him no, that he could not do something, he did not understand the expression on my face or inflection in my voice to know that I was angry.  He would start laughing because he thought my face looked funny that way.  So, I have a magnet on my fridge that shows human facial expressions and what they mean and we would use this picture frame smaller magnet to encircle the example of how we were feeling on a particular day and what that looked like to show him what people were trying to tell him without their words.  Language development was also difficult because he would “parrot” or repeat whatever he saw or heard on TV, but this was not necessarily communicating.  He would continually only want to talk to you about Star Wars or some other favorite movie, but this was not really having a conversation.  So, having personally experienced this throughout his life, I am keenly aware of how important both spoken language and the ability to read expressions are in our communication.   

I cannot think of any environmental condition where not reading body language would be a benefit except if there were some society where a lack of expression was somehow a beneficial survival technique and therefore the group that survived and was able to have offspring were quiet and expressionless people.  There was a study done by Dr. Paul Ekman on human facial expressions where he studied over 20,000 individuals from all cultures and races and studied their natural reactions and expression to basic human emotions.  He found that the expression of emotions was uniform in humans across all cultures, i.e. happy, sad, angry, etc. even among isolated groups, and therefore he concluded facial expression of emotions to be a biological function.  It was an interesting study and he has a website which can teach you to better read face and body language at http://www.paulekman.com/. 

Conclusion:

My conclusion is that both the development of spoken language combined with the ability to use signs and facial expression are all very important parts of language and the ability to communicate ideas effectively and efficiently with one another.  These developments have enabled our culture to grow and our species to become even more prolific today.

Piltdown Hoax

The Piltdown Hoax was an archeological find by Charles Dawson in 1912 who claimed to have found a piece of an ancient human skull in the southern English village of Piltdown.  He invited Arthur Smith Woodward of the Natural History Museum and paleontologist, Father Pierre Teilhard de Chardin to aide him in the dig and discovery.

Shortly after, Dawson dug up a jaw bone which looked more like the jaw bone of an ape, but was found in the same area.  It was thought to have been the jaw bone of the skull as the teeth were worn flat and did not reflect other ape teeth of the same era.  This find was thought to have been the missing link between ape and man and was dubbed “Piltdown Man”. 

Scientists cheered the news enthusiastically when the announcement came of the find.  The newspapers also came on board and due to the men’s reputations in the scientific community was readily and widely accepted without much question. 

Arthur Keith, who was a leading anatomist in London, also came on board.  He had a theory that big brains developed prior to upright walking.  This find emboldened his claims, so he was eager to accept the evidence of the bones to substantiate his own theories.

There was reluctance on the part of the public to challenge the find, as all the men bringing the fossils to light were highly respected.  Piltdown Man was accepted as the missing link between ape and human evolution, although no more fossils turned up after Charles Dawson’s death in 1916.  Current methods of dating fossils did not exist at that time, and the Natural History Museum did not allow outsiders to examine fossil remains.  So, contradicting them was very difficult.

But, finds in Africa and Asia in the 1920’s began to shed doubt on Piltdown Man.  The early human skulls found there were approximately 100,000 years old and much less human-like than Piltdown Man, which was supposedly an older find of more than 100 mya.  This began to cast doubt on Piltdown Man and motivated scientists to further study the fossils. 

After WWII scientists had more advanced methods of dating fossils using fluorine measurements.  As a fossil is exposed to ground seepage it collects fluorine from the ground as it fossilizes.  The longer the fossil has been in the ground, the more fluorine it accumulates.  Bones in the same area should contain the same amount of collected fluorine.  When the fluorine was measured in the skull and jawbone, there was a discrepancy that led scientists to investigate further.  It was exposed that the bones were much younger than originally thought.

This led scientists to inspect the bones more closely.  It was found that artifacts and bone fragments had been artificially stained to make them appear older.  Microscopic inspection also revealed that the teeth had been filed down to appear more human and the jaw bone had been cut in such a way that a vital connecting piece was missing so that one could manufacture a “fit” with the jaw bone to the skull, making it appear more human.

Eventually the jaw bone was accurately dated at less than 100 years old and came from a female orangutan and found that the specific pieces of the jaw bone which were missing would have definitely made it that of an ape and not a human.

Dawson’s motivation for the hoax was in his very ambitious nature.  He was a man who wanted to have a prominent place in the scientific community.  The discovery of Piltdown Man placed him there and clouded his judgment.  Since the exposure of Piltdown Man, Dawson is now known to have forged a half dozen other finds.  Woodward was clearly duped as he kept digging in Piltdown long after Dawson had died, but never found anything.  But he still seemed to blindly trust that Dawson had indeed found the missing link.  Arthur Kieth also had sufficient personal motives to perpetrate the hoax in that the find validated his own theory about the evolution of homo sapiens.  This theory then placed him in a very prominent place in the scientific community. 

At the beginning of the century scientists were revered and thought of as gentlemen who were above reproach.  This idea combined with the men’s own ambition made it possible for such a hoax to happen.  Also, the fact that the current fossil dating methods such as fluorine testing were not available yet made it difficult for anyone to challenge their findings.

Since the discovery of the fraud, the scientific community now understands that fraud is possible in their profession and takes greater care in their work to question and re-evaluate findings of colleagues through the scientific method.  This is a positive outcome of the hoax that has bettered the scientific community, the scientific method and the public's trust in science.

Good science must be based on objectivity.  When national pride or personal ulterior motives are involved, then science and the public are too vulnerable to those whose motives are only for themselves.  In order to be a good scientist and remove any human element, you must be willing to have other scientists and the public scrutinize your work.  This is the only way to be sure that whether it be personal motivations or simply human error, a hypothesis is thoroughly tested before it becomes a theory.

 

Comparison of Primate Locomotion

Ring Tailed Lemur

Lemurs (Prosimians/Strepsirhini)

Environment:  Lemurs are found exclusively in Madagascar, Madagascar has a coastal plain, high plateau and mountains.  The climate is tropical along the coast, temperate inland and arid in the south. The gallery forests that Ring-tailed lemurs prefer are rapidly being converted to farmland, overgrazed by livestock, and harvested for charcoal production.

Locomotion:

Lemurs are quadrupedal, meaning that they use all four limbs for locomotion.  Ring-tailed lemurs are more terrestrial, but also arboreal.  Sifaka lemurs are more arboreal and use vertical clinging and leaping.  They support themselves vertically by grasping onto tree trunks or other large plants with their knees and ankles tightly flexed.  They can spring away in a forwards or backwards motion by forcefully extending their long hind limbs. (Jurmain p 151)  Dwarf lemurs use a slow and cautious climbing form of quadrupedalism.  Their flexible hip joints permit suspension by hind limbs while using the hands in feeding.  Lemurs cannot use their tails for grasping.  (National Geographic - http://animals.nationalgeographic.com/animals/mammals/ring-tailed-lemur/)

How locomotion has been influenced by its environment:

The more than 60 lemur species have been influenced by its varied environment by both mainly arboreal and mainly terrestrial species being found in the differing climates of Madagascar.  Sifakas and indris are found more in the tropical and dry forests of the country and have a diet of leaves, fruit, bark and flowers.  They have developed their locomotion so much to an arboreal environment that on the ground their only locomotion is hopping.  Ring-tailed lemurs have a more varied omnivorous diet mostly of leaves, fruit, buds, bark and shoots but also of insects and small birds and chameleons.  They are the most adaptive of the lemur species spending equal amounts of time on both the ground and in trees.  Troop travel time is terrestrial.  The dwarf lemur, which is nocturnal and insectivorous, spends nearly all of its time in an arboreal existence.  So, within the 3 examples of the lemur species, we can see that the environment, habitat and diet of all 3 directly relate to their locomotion.

Sifaka

 

Dwarf Lemur

Spider Monkey (New World Monkey/Platyrrhini)

Environment:

Spider monkeys live in evergreen rainforests, semi deciduous and mangrove forests in Central and South America and as far north as Mexico.  They almost never come down to the ground.  Living mostly in the upper canopy, they prefer the undisturbed areas of the high forest. 

Locomotion:

While Spider Monkeys use a method of locomotion called semi-brachiation, a combination of leaping with some arm swinging, (Jurmain p 151) they are also quadrupedal, using all four limbs when walking or running.  When feeding they do so with brachiation, suspending themselves while eating rather than picking their food and moving it to an alternate location.  They also use their tails as additional support through the trees.  (National Geographic  http://animals.nationalgeographic.com/animals/mammals/spider-monkey/)

Spider Monkey

 How locomotion has been influenced by its environment:

The brachiation of the Spider Monkey is influenced by its environment as they spend almost all of their time in the upper canopy of high forests.  With a diet of fruits and seeds, leaves and aerial roots, it would be necessary to have for the Spider Monkey to have strong brachiation skills in order to maneuver quickly through the tree tops and obtain its food at the same time.  The adaptation of the use of the tails is also a feature adding to their agility.

 

Baboon

Baboon (Old World Monkey/Cercopithecidae)

Environment:

Baboons live in Africa or Asia preferring savanna and other semi-arid habitats.  A few baboons live in tropical forests. 

Locomotion:

Baboons move about quadrupedaly almost exclusively on the ground.  Unlike, New World Monkeys, Baboons do not have prehensile (gripping) tails.  While they do climb trees to avoid predators, seek food or sleep, they spend most of their time terrestrially.   (National Geographic Magazine - http://animals.nationalgeographic.com/animals/mammals/baboon/)

How locomotion has been influenced by its environment:

Living in the savannah regions of Africa and Asia, there is not a need for many tree climbing skills.  Baboons are opportunistic eaters foraging for most of their fruits, grasses, seeds, barks and roots.  But, they can also eat birds, rodents and the young of other small mammals.  Due to the diminished need for tree climbing, the baboon has adapted to its savannah environment by moving about more efficiently on the ground.  They also have developed rough spots on their protruding buttocks, called ischial callosities, which enables them to sit on the hard savannah ground for longer periods of time.

 

Gibbon

Gibbon (Lesser ape/Hylobatidae)

Environment:

Gibbons are tree dwellers living in the dense forests of Southern Asia. 

Locomotion:

Gibbons use brachiation as their primary method of locomotion.  If they do come down to the ground, they walk bipedaly using their arms high above their heads in a swinging motion for balance.  Gibbons are so good at brachiating that they can reach speeds of up to 35 mph and distances of 50 feet with one throw of their bodies from one tree limb to another.  

 (National Geographic http://animals.nationalgeographic.com/animals/mammals/gibbon/)

How locomotion has been influenced by its environment:

Gibbons spend most of their time in an arboreal environment, thriving on the abundant fruit trees in their tropical range.  Their food supply has aided them in developing the added agility and skill for maneuvering through the tree tops.  Their arms are quite a deal longer than their legs and their hands have also specially adapted to having better grip in the trees.  Gibbons do not have tails for balance, so their oversized arms are the main source of their locomotion.

Chimpanzee

 Chimpanzee (Great ape/Hominidae)

Environment:

Chimpanzees can be found in African rainforests, woodlands and grasslands.

Locomotion:

Chimpanzees normally walk on all fours, called “knuckle-walking”, however chimpanzees can stand and walk upright demonstrating bipedal locomotion. By swinging from branch to branch using brachiation, they can also move quite efficiently in the trees.  It is thought that Chimpanzees were once more of tree dwellers and therefore have retained the elongated arms for brachiating. 

(National Geographic - http://animals.nationalgeographic.com/animals/mammals/chimpanzee/)

How locomotion has been influenced by its environment:

Chimpanzees spend much of their time on the ground, however they sleep and eat in the trees and even make nests of leaves to sleep in. They are mainly fruit and plant eaters, but can also eat insects, eggs, and meat, including carrion. They have a varied diet which includes hundreds of foods.  Due to their varied environment, chimpanzees have adapted to be able to spend much of their time on the ground and in the trees with an equal amount of ease.  Chimpanzees also have a padded bottom enabling them to sit comfortably on the hard ground for longer periods of time.

Summary:

The following chart illustrates the various traits predominantly exhibited by each species. In the beginning while all 5 primates compared are quadrupeds and vertical climbers to some degree, being able to walk on the ground as well as climb trees (Jermain p 150), their natural environments have a great influence on their specializations.  The more arboreal the environment of the primate, the more brachiating is used as the main mode of locomotion and perhaps the use of a prehensile tail.  The more terrestrial the primate, the more quadrupedal and the addition of knuckle walking is observed.   In terrestrial primates, the arms are in more direct proportion to the length of the legs.  In more arboreal primates, the arms are more elongated due to brachiating as the main mode of locomotion.   As evidenced in the different body types and abilities of the 5 primates, the environment and habitat can play an important role in the evolution and adaptation of each species over time.   

Notable for the lemur species, which has over 60 species in Madagascar, is that it has maintained its equal limbs ratio although the sifaka spends most of its time in the trees as well as the dwarf lemur.  However, the sifaka does not brachiate, but rather leaps through the trees using its hing legs and arms to catch itself, and the dwarf lemur has maintained its very small proportions.  Ring-tailed lemurs, which  spend equal amounts of time on the ground and in the trees have equal arm and leg length.  As lemurs have adapted to their various environments undisturbed of other primate species, it is interesting to see how the lemur species alone has so many variations. 

	Environment		Locomotion						Distinctions
Primate	Arboreal	Terrestrial	Quadrupedal	Vertical Climbing	Leaping	Semi-Brachiation	Brachiation	Knuckle Walking	Elongated Arms	Equal Limbs
Lemur	X	X	X	X	X					X
Spider Monkey	X		X	X	X	X			X
Baboon		X	X	X						X
Gibbon	X		X	X	X		X		X
Chimpanzee		X	X	X				X		X