The Wild Life of Our Bodies

It is certainly true that enormous changes in human ecology have occurred in a very short time—ones that sharply contradict our evolutionary and environmental history. Cities, infrastructure, fast food, digitalization, and light pollution have produced a world that is purely a human creation and devoid of naturalistic elements. Various functional systems in the human body, such as digestion and immunity, are, in part, products of specific threats in the environment (e.g., predators or microorganisms) that challenged our existence millennia ago but were successfully negated in enough cases for us to continue living today. As result, these systems may find their niche not in today’s developed world but in the world of prehistory.

While one cannot deny the potential for serious consequences caused by an increasingly artificial world, Rob Dunn’s—as he puts it—idyllic portrayal of human ancestry in the introductory portions of The Wild Life of Our Bodies seems to speak more to the author’s own sentimental and nostalgic image for prehistory than to an accurate display of a period that he admits was ridden with predation, disease, suffering, and mercilessness unseen by most of today’s people. I will not deny the benefits of frequent exposure to the natural elements of our planet. However, an important characteristic of humans may negate Dunn’s assertions about the need for a re-infusion of naturalistic elements into metropolitan life. This characteristic is adaptability, both neurologically and genetically.

Advances in neuroscience, biological psychology, and genetics reveal a high level of adaptability in human behavior and physiology through neural plasticity (“plastic” meaning “easily shaped or molded”) and variability in gene expression. While classical evolutionary processes occur over millions of years, the human brain—and consequently the physiological functions controlled by it—updates its structure in real-time in response to environmental input. One might even say this is a main function of a nervous system: to actively adapt to the environment without the waiting period of reproduction, mutation, etc. Moreover, research in epigenetics (“epi-” meaning “above” or “around,” implying a form of genetic control exterior to DNA) has revealed that gene expression is not a fixed phenomenon determined at conception, but instead—though to a much lesser extent than the brain—is responsive to environmental conditions. Therefore, our bodies and brains may have a surprising ability to adapt to the seemingly inorganic aspects of developed civilizations—perhaps without facing the dire consequences foreshadowed by Dunn.

Furthermore, while the genome of a developing embryo “expects” a child to be born into a world similar to the one of prehistory, one must not forget the degree to which the brains of newborn infants are “blank slates,” uncontaminated by experience and learning. The initial experiences of an infant—whether they are those of a dense forest or a McDonald’s—become, for all intents, his or her “natural” environment. Environmental stimuli, working in an interdependent relationship with one’s genome, carve the early architecture of an infant’s brain. In other words, physiological response tendencies (i.e., how one’s brain or body responds to various environmental stimuli) and gene expression are in a perpetual feedback loop with the environment (via the sensory systems and the brain) that allow it to adjust accordingly to the world the infant occupies. The result is a developed adult who has, at least in part, adapted to the world of today – possibly mitigating the risks alluded to by Dunn.

Finally, while the incidences of certain problems, like autism, are on the rise in today’s culture, it is important to realize that any system is going to have its problems—but the ones that arise will be specific to that system. Human systems in prehistory had problems such as predation and dysentery; today’s systems have autism and diabetes. Pick your poison.

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