Blog Post: Human Variation & Race
Environmental Stress: High Altitude
High altitude serves as an environmental stressor in that it disrupts human homeostasis through the reduced amount of oxygen available in the air. This condition is called hypoxia and stresses the body primarily through the cardiovascular and respiratory systems. Mountains and other high-altitude areas may be thought of as high altitude at elevations above 2,500 meters (8,200 feet). At elevations of more than 8,200 feet, the atmospheric pressure is reduced, and in turn, fewer oxygen molecules are delivered into the lungs with each breath. In tissue, oxygen is limited, energy production is limited, cognition is limited, and physical performance is limited.
Short-Term Adaptation
Adaptation: Increased respiration and heart rate.
A human adapts by increasing respiration and heart rate to try and circulate more oxygen around the body to maintain oxygen levels in the tissues during high-altitude travel. This is a short-term adaptation that can help maintain oxygen availability in otherwise poorly oxygenated areas.
Facultative Adaptation
Adaptation: Increased production of red blood cells.
Facultative adaptations result in changes such as increased hemoglobin concentration (the body produces more red blood cells to now accommodate transport of oxygen in low-oxygen environments). Again, this is not permanent, and if one starts a low-altitude lifestyle, the facultative adaptations will revert to the original state.
Developmental Adaptation
Adaptation: Greater birth weights among long-term high-altitude populations.
Populations such as Tibetans and Andeans have developed developmental adaptations that enable women to have babies with greater birth weights in high-altitude habitats. This trait enhances infant survival in environments where low levels of oxygen graduate fetal growth and development.
Cultural Adaptation
Adaptation: Modifications to lifestyle and infrastructure.
High-altitudinal communities, such as those in the Andes or Himalayas, have adapted culturally through the development of cities, homes, and practices that facilitate life in thinner air. These human adaptations include adopting slower-moving paces of physical activity (aerobics, hiking, etc.), different agricultural practices, and architectural structures that assist in heat or oxygen retention.
Why is Studying Human Variation Across Clines Important?
Investigating human variation in the context of environmental clines, such as altitude, allows us to understand how humans adapt biologically and culturally. This information can allow public health practitioners to consider environmental exposure and subsequent effects, such as acute mountain sickness for travelers, and ways to support childbirth in high-altitude environments. For example, understanding how a climber may perform at high altitude in terms of the amount of oxygen they will require to be healthy will better the medical treatments for climbers or military operations in high geographical environments.
Is Race a Useful Explanation for These Adaptations?
Race is not a valid scientific explanation for the adaptations listed above. People in different parts of the world are able to live at high altitudes, but only some of them will develop certain genetic or developmental traits, depending on how long they have lived there. For example, both Tibetans and Andean people have heightened adaptations to altitude, but these traits evolved differently. This supports an explanation that adaptation comes from a consistent environmental factor, and not race. Cline studies allow for a valid, scientific explanation of variation that is somewhat more valid than race, which is a social construct and not a biological fact.
1. Describe stress (3/5) - "through the reduced amount of oxygen available in the air."
ReplyDeleteTo clarify, it isn't less oxygen. It is less oxygen *pressure*. The human body evolved closer to sea level and as a result, our physiology is designed to transfer oxygen across membranes at a certain air pressure. When you reduce that pressure, our system doesn't work as well.
"fewer oxygen molecules are delivered into the lungs with each breath"
No, they are just more dispersed.
Beyond that, there is another aspect of hypoxia that is important to consider, and that is the impact of hypoxia in pregnant women. A fetus already gets reduced oxygen content via the placental system, so if you reduce that further in a low oxygen environment, you run a greater risk of poor development or even fetal death in a high altitude environment, unless your population has adapted over time to that stress.
2. Adaptations
a. Short term (5/5) - Good.
b. Facultative (5/5) - Good description.
c. Long term (5/5) - Re: Higher birth weights, I had to look this up. There are studies that suggest otherwise, such as this study from Colorado, where birthweights at higher altitudes were *lower* overall.
https://pmc.ncbi.nlm.nih.gov/articles/PMC7050200/#:~:text=Compared%20to%20low%20altitude%2C%20infants,low%20birth%20weight%20by%2027%25.
But looking specifically for higher altitude populations, such as those in Tibet, indicate what you reference, with Tibetan populations having higher birth weights than those in lower altitudes of China. This suggests that this is a *very* long term adaptation over many generations, and the population in Colorado is too new or too transient to develop the traits.
https://pmc.ncbi.nlm.nih.gov/articles/PMC2789738/
Would have been helpful for you to provide a source for this.
d. Cultural (4/5) - Okay, but it would have been better to focus on one practice and dig a bit deeper into the detail? This is a bit too general. The use of terracing for agriculture is a great example, as is the use of llamas or alpaca to carry heavy loads at those high altitudes.
3. Benefits (5/5) - Very good.
4. Racism (8/10) - "This supports an explanation that adaptation comes from a consistent environmental factor, and not race."
Okay, but you are coming at this from a post hoc argument, kind of from the conclusion backward. Can we think about the different relationship between race and adaptations vs. the environment and adaptations to get a clearer grasp of the issue here? Can we actually use race to help us understand human variation? Recognize that it is entirely possible to answer this question with a decisive "no".
To answer this question, you first need to explore what race actually is. Race is not based in biology but is a social construct, based in beliefs and preconceptions, and used only to categorize humans into groups based upon external physical features, much like organizing a box of crayons by color. Race does not *cause* adaptations like environmental stress does, and without that causal relationship, you can't use race to explain adaptations. Race has no explanatory value over human variation.