Biological Adaptations to High Altitudes in Ecuador (Riya Johnson)

Introduction

After living in the mountains of Ecuador for a few days, my mother began experiencing headaches and nausea. I learned that she was suffering from mountain sickness, a result of hypoxia: a lack of oxygen supply in body tissues that increases at higher altitudes. Additional symptoms of mountain sickness include fatigue and breathlessness. However, my mother’s symptoms soon abated. Knowing that evolution occurs across generations rather than within your lifetime, I wondered why her body had adapted so quickly. I soon found an answer to my question: there is not just one type of adaptation.

Genetic vs. Physiological Adaptations

I was most familiar with genetic adaptations: as a response to natural selection, populations’ gene pools change over time to adapt to their environments. Thus, these adaptations are inherited and cannot be reversed. My mother displayed acclimatization or a physiological adaptation: during their lifetime, individuals adapt to new environments rather than inheriting traits from past generations. Since physiological adaptations are reversible, when my mother returned to Boston, she became re-acclimatized to the lower altitude.

How Does Acclimatization to High Altitudes Occur?

How exactly did my mother’s body manage to overcome mountain sickness within a few days? Due to the lack of oxygen molecules in the air, her body had to use the oxygen that was available more efficiently to achieve homeostasis. Thus, it synthesized more red blood cells and oxygen-rich hemoglobin to transport oxygen to body tissues. Also, the diameters of her arteries and veins increased to allow more blood to flow through them at once and thus accelerate oxygen flow.

Do Locals Have Athletic Advantages?

Our guide in mainland Ecuador explained that if local athletes participated in a short-term competition at a lower elevation, they would have an advantage, for their bodies would create more red blood cells. In the long term, though, they would become acclimated. Our guide has observed that residents of Quito excel in sports on the coast, for there is a lot more oxygen to fill their lungs. However, after 10 minutes of rapid energy expenditure, they have depleted their supplies of supersaturated blood. Even the cars go very fast on the coast but use up their gasoline rapidly. As another example, Olympic cyclists would train in Ecuador for a month to maximize their red blood cell production during the competition.

What Are Locals’ Adaptations to High Altitudes?

Genetic Adaptations

When I asked our guide about locals’ genetic adaptations, he shared that their lungs are the same size as yours and mine, but their thorax and lung capacities are slightly greater. Most residents have larger chests so their lungs can breathe more deeply and absorb more oxygen.

Another genetic adaptation is visible in indigenous peoples, especially Otavalos. Natives are shorter because being tall is disadvantageous in the Andean zone due to the rocky terrain. Having lower centers of gravity allows them to navigate the mountains more easily.

Cultural or Behavioral Adaptations

However, our guide explained that locals have also developed cultural, or behavioral, adaptations: actions or materialistic items used to improve living conditions. At low altitudes, you do not have to breathe deeply because oxygen is readily available. Ecuadorians lose a significant percentage of their oxygen intakes, so they inhale more air. They also pace themselves via small, measured steps, for they would get tired otherwise. Our guide has hiked with an 86-year-old who conquered difficult treks by adopting this steady gait! There is an evident tie between your environment and biology that I am excited to continue investigating.

For completeness, the fourth type of adaptation is developmental, or ontogenetic, adaptations: individuals develop traits when they reach a certain age. Unlike with acclimatization, the ability to make such developmental changes is inherited, the developed traits are irreversible, and the transformations do not occur at any point in your life when you are exposed to a new environment.

Sources

1. Thank you to our Abercrombie & Kent guide in mainland Ecuador for sharing the information upon which this post is based.
2. Essentials of Biological Anthropology by Clark Spencer Larsen