On Modern Times and Evolution

One thing that never fails to trigger an existential crisis within me is hearing somebody say anything along the lines of “You kids have it too easy these days.” Whenever I hear these words, I would always think to myself that that is how things should be going, considering that we are on the receiving end of an onslaught of technological advances, especially on the medical front. But this thought sparks the question: Is modern medicine hampering our evolution?

Extinction is the Rule

Carl Sagan stated that extinction is the norm and adaptation is the exception. Clearly, us humans fall into the latter half of this statement. We were able to innovate and develop more efficient tools compared to what our Neanderthal predecessors had, ultimately leading to our more successful conquest in braving the ever-changing world that we live in. Our species has been surviving for about 200,000 years now, continually evolving and adapting to our surroundings. With the advent of modern medicine, however, it is no surprise that some people argue that we are getting in the way of natural selection by allowing the weaker ones to reproduce, thus allowing “inferior” genes to persist in the gene pool.

Superhumans

Despite these concerns, there are actually multiple pieces of evidence that suggest that our species has not yet stopped evolving. Take for example the Badjao people of Southern Philippines and Peninsular Southeast Asia. Ultrasound images show that the size of their spleens are 50% larger than average, suggesting that these nomadic people who spend most of their days free-diving to gather resources actually evolved to adapt to their environment. The spleen is a reservoir for oxygenated red blood cells, so that when it contracts while diving, the body gets an oxygen boost, similar to how modern scuba tanks work. Obviously, larger spleens will be able to accommodate more oxygenated red blood cells, thus allowing for longer dive times. Llardo, et al. (2018) gathered data of spleen sizes from both divers and non-divers of the Badjao people, and data show that a larger spleen size is consistent throughout their population, which means that the enlarged spleens are not just the result of regular diving, but rather an evolutionary adaptation that has been passed for generations.

Badjao shows off the wooden mask he uses for diving, from https://www.theatlantic.com/science/archive/2018/04/bajau-sea-nomads-diving-evolution-spleen/558359/

Another example is the dwellers of the Tibetan plateau, wherein they have evolved to have higher birth weights and higher oxygen saturation. The higher birth weight allows them to survive periods of shortage, while the higher oxygen saturation allows them to live in altitudes up to 4,000m, where oxygen levels are about 40% lower than at sea level. These genetic adaptations are said to be the fastest that a human population has evolved, occurring only in a span of 3,000 years, according to Yang et al. (2017).

A group of Tibetans can easily scale up slopes even with the thinning atmosphere due to genetic adaptations that enable them to have higher oxygen saturations, from https://www.sciencemag.org/news/2017/04/mutations-may-reveal-how-tibetans-can-live-world-s-highest-plateau

But these adaptations are only observed with nomadic populations who do not have regular access to modern technology and medicine. What about the rest of us in modern society? Are these quarantine measures getting in the way of our evolution? Have we doomed ourselves to extinction?

Of course not.

Natural Selection is still very much at play.

In a strict scientific context, evolution is the change in heritable characteristics of a population over successive generations. Species change over time because individuals with advantageous traits are more likely to survive long enough to reproduce. Considering that most of the accomplishments of modern medicine is mostly directed to the elderly who are well past the age of reproduction, the effect of modern medicine on human evolution is very little and not as significant.

If we turn our attention to a modern hospital, we see that this environment has been fundamental in decreasing mortality among us. With genetic screening, we can effectively identify genetic defects and perform selective abortions. On the other hand, the hospital environment also favors the emergence of drug-resistant pathogens.

Outside of the hospital, we see that natural selection is still in play because of miscarriages, stillbirths, childhood death, and infectious diseases. On a global scale, infectious diseases are still the top contributor for mortality. As morbid as it sounds, the pandemic that we currently have at hand is actually natural selection in action. A number of our genes affect our immunity, and this affects an individual’s susceptibility to disease and the severity of manifested symptoms when infected. This creates an opportunity for natural selection.

Based on these situations, we cannot say for sure that modern medicine has absolutely favored or opposed human evolution.

So fret not, dear reader, for we are still evolving as long as we are still breathing. In fact, this pandemic can even affect how we evolve, for a part of our DNA is from viruses that previously infected humans. If the government is firm on imposing lockdowns without adequate testing and aggressive contact tracing, then the next generations of Filipinos might be less susceptible to future strains of coronaviruses.

---

References:

Cable News Network. (2010, July 2). Tibetan DNA study reveals human evolution. CNN. http://edition.cnn.com/2010/HEALTH/07/02/tibetans.evolution/index.html.

Ilardo, M. A., Moltke, I., Korneliussen, T. S., Cheng, J., Stern, A. J., Racimo, F., … Willerslev, E. (2018). Physiological and Genetic Adaptations to Diving in Sea Nomads. Cell, 173(3). https://doi.org/10.1016/j.cell.2018.03.054

Yang, J., Jin, Z.-B., Chen, J., Huang, X.-F., Li, X.-M., Liang, Y.-B., … Qu, J. (2017). Genetic signatures of High-altitude adaptation In tibetans. Proceedings of the National Academy of Sciences, 114(16), 4189–4194. https://doi.org/10.1073/pnas.1617042114