Every aspect of the organismal design, including organismal nutritional requirements, which may be defined as the nutritional input that’s required to produce physiological competence, is a function of evolution via natural selection. This Darwinian view of nutrition is undoubtedly unfamiliar to a lot of people, as mainstream nutrition may be said to be of a non-evolutionary nature; however, from an evolutionary point of view, it seems self-evident that there’s a Darwinian basis to nutrition. After all, it makes absolutely no sense for that aspect of life to be exempt from the natural laws that govern every other aspect of it.
Evolutionary science, spearheaded by Darwin, has the potential to bring order and structure to the field of nutrition
The field of nutrition is riddled with disagreement and conflict. Some people claim that we would all be best off we adhered to vegan diet principles; others hold the belief that the grain-heavy diet that’s pushed by governmental health agencies is a truly wholesome diet; and yet others again say that it doesn’t really matter that much what we eat, as long as we watch our portion sizes and stay on top of our caloric intake. Not only that, but there’s a lot of debate about the specifics, in the sense that there’s no universal agreement as to how much sugar, monounsaturated fat, fiber, etc. it’s healthy to take in.
The main reason why this is the case is that the field of nutrition lacks a foundational paradigm that supports and guides the field. Seeing as all organisms are biological systems that evolve via Darwinian processes, any truly constructive paradigm would arguably have to be Darwinian in nature and be based on biological and evolutionary sciences. This is something several sharp nutritionists and scientists who appreciate the process of evolution have recognized, but it’s unfortunately something the larger nutritional community hasn’t picked up on.
Darwinian nutrition
Populations evolve as a result of the selective pressures they face. Given that energy procurement is a prerequisite to survival and reproduction, it goes without saying that food and nutrient availability is one of the major forces affecting the evolution of life. Those organisms that do well under the existing nutritional conditions stand a better chance of passing on their genes to future generations than those organisms that don’t do as well, and as a result, traits that are beneficial with respects to survival and reproduction in the present become more common over time. Seeing as this change occurs as a result of variation in reproductive success resulting from inter-individual variation in nutritional flexibility, tolerance, and needs, it goes without saying that this evolutionary process shapes those aspects of organisms.
To illustrate this, let’s imagine that a large group of animals of a particular species occupies a particular natural environment that’s remained fairly stable for quite some time. The animals eat a mixed diet composed of both plants and other animals. For some reason (e.g., due to climate shifts), the environment changes in such a way that the animals in question are no longer able to get a hold of as much meat as before; they have to rely more on plant sources of energy. This change produces an evolutionary mismatch situation (i.e., a situation involving genome-environment dissonance) and is likely going to increase the selective pressure that acts on the population.
Those animals that are best able to tolerate the new nutritional conditions will be at an advantage, in a Darwinian sense, when compared with those animals that find it difficult to cope. Traits related to digestive and metabolic functions, gastrointestinal morphology, and brain composition and size will be particularly important in such a scenario. Over time, the traits that are advantageous under the new, meat-scarce conditions become more common. The effects on the population will depend on the impact the environmental change has on the animals’ reproductive success. If the change has a major impact on inter-individual reproductive success, the population will change more rapidly than if the impact is small.
Typically, when there’s a shift in the plant-to-animal ratio of the diet of an animal population, significant changes in organismal morphology occur over time. Under plant-heavy conditions, it’s generally a plus to have a fairly large digestive system that is able to process a lot of bulky plant matter, whereas the opposite is true in a meat-heavy situation. Moreover, the latter conditions are more supportive of brain augmentation than the former, among other things.
The key point with respects to nutrition is that these processes shape the nutritional needs of the animals, due the fact that they continually act to bring organismal biology in synch with environmental conditions. In the scenario above, those animals that do best on the altered diet are favored by natural selection. In other words, it’s those animals that have nutritional requirements that are best aligned with the nutritional situation that are favored, and hence, it’s those requirements that are going to become more common over time. Health is tightly linked with fitness in Darwinian evolution, particularly in natural settings; hence, it goes without saying that this has major implications for nutrition and medicine.
Darwinian nutrition depicted
Organisms do best when there is agreement between their nutritional intake and biological design
Organisms appear specifically adapted, with respects to their physiological design, to a particular diet. Not only that, but they seem to need a particular type of diet in order to stay healthy and vibrant. If you take an organism out of its natural habitat and insert it into a different milieu, it’s bound to get into trouble. For example, if you remove a zebra from the African savanna, enclose it in a zoo, and feed it a diet that differs in several respects from the diet it ate in the wild, it’s not going to fare so well.
This seems rather obvious and makes immediate sense in light of the things outlined earlier. It’s also something we intuitively understand. Unfortunately though, it’s something we often forget or fail to notice, particularly when the environmental change is gradual and slow as opposed to abrupt. Also, we seem to be under the belief that we humans are of a special design and don’t have to conform to the rules of nature. Obviously, that’s an illusion.
Some important things to keep in mind
Various health and lifestyle-related factors have to be taken into account when the nutritional requirements of a population or individual are ultimately to be determined
It’s important to recognize that any major change in the exposures or activity pattern of a population may have nutritional implications. For example, if a group of humans suddenly start spending more time indoors, and hence, are exposed to less sunlight than before, they may naturally need to take in more vitamin D via their diet in order to maintain good health. Furthermore, individuals may differ somewhat with respect to their nutritional needs even if they belong to the same group. This inter-individual difference exists not only because of genetic variation (Note that certain genetic disorders are associated with altered nutritional needs), but also because of variation pertaining to physical activity pattern/level, disease load, stress levels, etc. If for example a tiger were to be infected by a parasite and develop a chronic illness of some sort, it would be expected to crave and require a different mix of foods/nutrients, for the simple reason that such an insult will have physiological, immune-related effects.
Epigentic functionality allows for adaptation on much shorter timescales than what selection on allele frequencies permits
If for example a human is exposed to energy-deficient conditions early in life, such as in utero, its phenotypic development will be adjusted accordingly as a result of plasticity in gene expression. Most likely, the person in question won’t grow to be as big and tall as if he/she were exposed to energy and nutrient-rich conditions early in life. This adjustment may simply be perceived as an acute response or adaptation to nutritional meagerness; however, it may also be understood as adaptive accommodation to expected future conditions of life. Irrespective of the view that one gravitates towards, it’s important to recognize that there’s a ceiling as to the level of customization that can be achieved this way. Additionally, it’s important to acknowledge that this epigenetic feature is ultimately a product of ‘conventional’ Darwinian selection. In other words, it’s by no means “something different” that falls outside the bounds of Darwinism.
Co-living allows for ‘nutritional networking’
No organism lives in complete isolation. This is relevant to discussions about nutrition, as organisms affect each other’s health and fitness by shaping the nutritional conditions they live under. For example, a person’s gut microbiota acts on and evolves in response to the foods that that person eats. If the individual in question suddenly starts eating considerably more of a certain type of plant, those microbes that are best able to utilize the substrates that are present in that plant will come to find themselves in an advantageous position. This again will affect other organisms in the vicinity, including the human host, in part because various products (e.g., short-chain fatty acids) will result from the bugs’ actions. The person in question may also come to acquire new bacteria, such as via contact with other humans or through his diet, something that may have consequences for the digestion and utilization of certain foods within the system. What’s important to recognize though, is that while seemingly intertwined with the person in question, such organisms are not a part of him. Rather, they are a part of his environment; and hence, represent a selective pressure.
A key point: Every part of the organismal design is shaped by evolutionary processes
The processes and principles outlined in this article are universal, in the sense that they shape the evolution of all living things on this planet. In other words, they aren’t just relevant in the context of human nutrition. Moreover, Darwinian processes don’t just shape the nutritional needs, preferences, and tendencies of organisms, they also shape every other part of the organismal design, including functions and requirements related to sleep, sun exposure, physical activity, and social behavior, among other things. In other words, the paradigm described in this article can be extended to include pretty much everything that has to do with organismal needs, behavior, and health, all of which is covered by the umbrella of Darwinian medicine 🙂
Pictures: 1: Created using pictures from unsplash.com. 2: Created using pictures from freepik.com. 3: Photo by Victor Freitas on Unsplash. 4: Creative commons picture by Christoph Bock. Some rights reserved. 5: Creative commons picture. Some rights reserved.
