Human Variation

1. The effects of high altitude on humans is considerable. Air is comprised of nitrogen (79.04%) and oxygen (20.93%) making up the majority of each breath we take. This composition of air remains consistent, whether we are at sea level or at altitude.  However, with altitude, the partial pressure of oxygen in this air (how many molecules of oxygen are in a given volume of air) changes. At sea-level, the partial pressure of oxygen is 159 mmHg, whereas at 8,848m above sea level (the summit of Mt Everest), the partial pressure of oxygen is only 53 mmHg. 

At high altitudes oxygen molecules are further apart because there is less pressure to push them together. This effectively means there are fewer oxygen molecules in the same volume of air as we inhale. This disturbs homeostasis and can ultimately be fatal.

2. Short Term Adaptation: acute moutainsickness (also known as acute altitude sickness) is a group of general symptoms that are brought on by climbing or walking to a higher and higher altitude (elevation) too quickly. High altitude is defined as 8,000 - 12,000 feet above sea level. Very high altitude is 12,000 - 18,000 feet, and altitudes above 18,000 feet are considered extremely high altitude. Hypoxiathen occurs because the body doesn’t have enough time to adapt to the lower air pressure and lower oxygen level in the air at high altitudes. The short term adaption occurs: increasing of the breathing rate. This then boosts the blood oxygen, but not to normal levels. The body needs to adjust to operating with less oxygen than usual. When you don’t give your body time to adjust, you will develop symptomsincludingdizziness, fatigue, shortness of breath, loss of appetite, sleep problems and a general loss of energy. These symptoms usually begin within 12 to 24 hours of arriving at a high altitude. However, these symptoms lessen within a day or two as the person gets used to the altitude.

Faculative Adaptation: High altitude pulmonary oedema (HAPE) is a dangerous build-up of fluid in the lungs that prevents the air spaces from opening up and filling with fresh air with each breath. When this happens, you become progressively more short of oxygen, which in turn worsens the build-up of fluid in the lungs. This can be fatal within hours. HAPE usually develops after 2 or 3 days at altitudes above 2500 m. Typically you will be more breathless compared to those around you, especially on exertion. You will experience the same symptoms of hypoxia, but you may also develop a cough and this may produce white or pink frothy sputum. The breathlessness will progress and soon you become breathless even when you’re resting. Heart rate may be fast, the lips may turn blue and body temperature may be elevated.

Developmental Adaptation: Groups living in the highest elevations have different developmental adaptations.  For example, Andeans exhibit a hematological developmental adaptation to the thin air by developing an ability to carry more oxygen in each red blood cell (they have higher hemoglobin concentrations in their blood). Basically, they breathe at the same rate as people who live at sea level, but the Andeans have the ability to deliver oxygen throughout their bodies more effectively than people at sea level do because having more hemoglobin allows them to carry the oxygen through the blood system.  Tibetans, as pictured below, have a respiratory developmental adaptation.  In contrast, they increase their oxygen intake by taking more breaths per minute than people who live at sea level. Additionally, theyhave a second biological adaptation, which expands their blood vessels, allowing them to deliver oxygen throughout their bodies more effectively than sea-level people do.Tibetans' lungs synthesize larger amounts of a gas called nitric oxide from the air they breathe. The nitric oxide increases the diameter of blood vessels, which suggests that Tibetans may offset low oxygen content in their blood with increased blood flow.

Cultural Adaptation: A cultural adaptation has been the control of fire and an expanded tool kit that included bone needles to make complicated clothing that protected the body in a significant way. Today, climbers also use oxygen tanks and masks when climbing the summits.  

3. In studying human variation from across environmental clines we can better understand how our environment has affected us as humans and what adaptations have resulted as a way of helping us survive. For example, it is clear that the Tibetans and Andeans have biologically adapted to high altitudes through hematological and respiratory developmental adaptations.  Wouldn’t it be of great importance to study how and perhaps find cures to different conditions in which low hemoglobin levels reduce the ability of the blood to carry oxygen like anemia?  

4. Studying environmental influences on adaptations is a better way to understand human variation than race because race does not account for human biological variation. As we learned in this weeks lesson, race has only been around for a few hundred years. Race-based interpretations of human diversity limit and obscure scientific research into the true sources, patterns, and importance of human variation. There is no clear or stable relationship between easily observable traits such as skin color. What is inside our bodies is literally millions of genetic and phenotypic traits, which are notobservable. Race is a modern idea and a social construct and frankly it cannot cause any specific adaptation. Given this information I would not use it to understand the variances of the adaptations I listed in #2. 

Piltdown Blog

In February of 1912 a laborer digging at Barkham Manor near the village of Pilton found a piece of skull that he reportedly then gave to Charles Dawson, an amateur archeologist.  Charles Dawson then on approached Sir Arthur Smith Woodword, a very well known geologist and together they set off to continue digging at the site. They found an ape-like jawbone with human-like teeth that seemed to link it to the skull Dawson got from the laborer.  It appeared they had found the earliest human.  

What’s important to understand is that the British had no early man.  The French and the Germans had many Neanderthals and they were very proud of their discoveries and the British wanted one of their own, something to “rival the Germans’ ape man.” They were jealous.  The finding meant fossil evidence for the earliest humans and their primates; a creature part ape and part human; a fossil that connected humans with apes and ultimately proof of Darwin’s theory.  We know this to be true in todays day, but back in the early 1900s they did not have the technology, so this had huge scientific significance in 1912. On December 18, 1912 they presented the world with “the earliest Englishman” – Piltdown Man. However, some experts remained skeptical.

They found a tooth matching predictions of the size of the canine and even found another skull and tooth of Piltdown Man Two.  This find made Pildown genuine – no one could question the initial find now.  They even had the backing of the Natural History Museum, but in 1953 the world found out that Piltdown Man was a fake. It started with a chemical test to date the fossils (they were estimating the nitrogen content).  They found the teeth had been filed down.  The skull was a different age then the jaw – even worse the jaw was not even human! The fossils had been boiled and carefully stained with chemicals to make them look old. The canine tooth seemed to have been made in a rush because it was crudely filed and colored with paint.

No one knows for sure who did it, but the person who had the most to gain from the hoax was Charles Dawson. They say his ambitions to make a name for himself were limitless.  This ambition can be portrayed as a human fault. The need for a sense of pride also played a role because otherwise maybe the Natural History Museum would have taken more steps to verify the fossils instead of just accepting it and announcing it to the world. It was like they just wanted to win the competition, they wanted to be the best. I do not think that it’s possible to remove the “human” factor from science because it is humans who are doing the research.  How can someone remove something that is natural to them? After all is not our humanness that makes us human? We can reduce the chance of errors like this happening again by putting procedures into place, but I do not suggest removing the human factor from science. Our humanness is what makes us curious and creative; it leads us to ask questions and find answers.  We need that in science, too. A life lesson that I can take from this is to remember to be humble and of course, don’t lie because the truth always comes out.

Analogy & Homology Blog Post

Homologous Trait: limbs

Two species that share a homologus trait are a human and a dog.  Humans are of the primate genus Homo, specifically a member of the species homo sapiens.  Dogs are mammals that are of the genus Canis and are a subspecies of wolves.  The dog was the first species to be domesticated and they come in many different breeds.  They have long been associated with humans, which has led them to be uniquely attuned to human behavior. 

The arm of a human and the leg of a dog are considered homologous structures because they have a similar underlying anatomy.  Our arms have the same bones and joints as the front legs of dogs. As the photo depicts, we share radius', ulnas, carpals, metacarpals, and digits. Humans use their arms for a range of things, but to name a few they are used for lifting, carrying, or throwing things. Dogs use their front legs for walking, running, and digging.  Researchers speculate that the common ancestor of the human and dog is the insectivore.

Analogous Trait: Flippers

Two species that share an analogous trait are penguins and dolphins. Penguins are from the Spheniscidae familyand evolved from flying birds. They reside in the Southern Hemisphere. They are usually in an upright position and walk on short legs. Dolphins are from the cetacean family and evolved from land-dwelling mammals of the artiodactyl order. They generally prefer warmer climates.  Although they live in the ocean, dolphins are still classified as mammals.  They have a dorsal fin that runs the length of the body. 

Penguins and dolphins both use their flippers for progression through water. Specifically, they both use their flippers to change direction and to manage their movement while in the water. The penguin’s flippers are supposed to be the vestiges of wings because they evolved from flying birds, however now they use their flippers to swim through water and cannot fly. Given that dolphins are mammals and penguins are birds, this is an example of convergent evolution where analogous structures with a similar function develop from unrelated bodily structures. These species do not share a recent common ancestor, but these similar appendages (flippers) evolved to help them survive in an aquatic environment.

Scientific Method Scenario Blog Post

1.    Hypothesis: It is possible that the student is hungry and does not have enough energy to stay awake. 

2.    Test:

a.    I would test this hypothesis by bringing a nutritious energy bar to class and offering it to the student before class begins. I am altering conditions by having the student eat before attending class.

b.    If the student stayed awake, this would support my hypothesis.

c.    If he fell asleep anyway, it would suggest my hypothesis is falsified.

3.    An example of an untestable, unfalsifiable explanation would be that as a child the student was hypnotized by a stranger and instructed to fall asleep during this exact class.