Like A Glove: How the Earth and the Brain Fit Together

earth brain

When I was growing up in Coney Island, I remember kids talking about what the future held in store for the evolution of human beings. Many children in New York City during the 1980s experienced respiratory problems due to the incineration of waste in our neighborhoods by the department of sanitation. People did not foresee that community action would result in the abandoning of garbage incineration in the 1990s. Instead, they envisioned a smoggy future in which only those of us with nostrils and lungs possessing superior filtering capabilities would be free from the respiratory complications our environment presented.

While many details of these evolutionary premonitions were downright silly (for example, comically large noses; we were kids, after all), they were correct insofar as the underlying notion that these changes were shaped by environmental demands. Thus, if air quality were permanently tarnished, then that would lend an advantage, evolutionarily speaking, to individuals who are more capable of filtering out toxins from the air we breathe. The principle of evolution by natural selection was evident in this thought process. For those of us who understand and accept evolution as the guiding force that shapes the appearance and behavior of all living organisms, the relationship between the Earth and the brains that evolved here couldn’t be more implicit.

The old adage “You are what you eat” really does not do justice to the foundations our brains have in Earth-born demands, of which diet is one. It is well understood that certain kinds of foods and food-preparation techniques (for example, fish and cooking said fish) played a large role in human-brain evolution and development. The fish diets of some of our evolutionary ancestors provided nourishment that has been linked to bigger and better brains, which facilitated our predecessors’ survival and subsequent reproduction.

Furthermore, while cooking meat before ingestion does wonders for taste, it also accomplishes some of the early stages of digestion. Because this practice eases the digestive system’s responsibilities, we beefed up our brains relative to our guts. What is left out of the “You are what you eat” saying is that humans were shaped by the environmental demands most relevant to obtaining the foods we tend to consume.

Perhaps the best example of this is color vision. Our visual systems have the ability to detect differential absorption of photons coming from light sources such as the sun; we perceive these differences as color. Discriminating between the color of a fruit on a tree and an animal hiding in the bush was an enormously advantageous weapon in early humans’ hunting and foraging arsenal. Vision is the primary sensory system of the modern human central nervous system, and many years of research have revealed how highly specialized our brains are for processing visual stimuli. The occipital lobe in the posterior of the brain has multiple maps that analyze every nuance of the visual world.

The organization of components in the visual system is shaped not only by attributes of the Earth itself (such as atmospheric details) but also by our place in it. For example, while humans and many other sighted species possess a single fovea in each eye, many kinds of birds have two. The fovea is the area of the retina where visual acuity is highest. Some birds have evolved one for when they are flying and an additional one for when they are walking. Therefore, the Earth, as well as the particular niche an organism fills, shapes these brain-based sensory processes.

To further explore this idea, it is worth thinking about how life might evolve differently on other planets. For example, what might the brain of an organism that evolved in the dark waters of a frozen moon look like?

For starters, there would likely be no brain area devoted to visual processing. In a dark, aqueous environment, chemosensation (for example, lobster antennae) would probably be a better way to navigate that kind of world. Although on Earth, some creatures that occupy the deep, dark seas are bioluminescent. If such organisms exist on my version of Europa (one of Jupiter’s moons), then even a rudimentary visual system to pick up the faint glows of bioluminescent morsels might be a means to a meal. We see some very basic visual systems in organisms on Earth in these kinds of niches.

In addition to the environment itself, the availability of resources and how best to obtain them are major determinants of evolved traits. We have many extreme environments on Earth, such that they can be informative to this thought exercise. There are places on our planet where organisms have evolved to survive in harsh conditions, such as in concentrated pools of hydrochloric acid. These life forms have a unique biological makeup that allows them to survive and a specialized repertoire of behavior that allow them to thrive.

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