The cementing of adaptations OR Why we can't live without Selenium

This post is borne out of a conversation Aisling and I had last night.

There are a host of very minor trace metals that are actually necessary components of our diet. These include Selenium, Copper, Chromium, and Magnesium, just to name a few. What happens when we don't get an adequate supply of these metals? From various Wikipedia articles...

"Selenium deficiency can lead to Keshan disease, which is potentially fatal. Selenium deficiency also contributes (along with iodine deficiency) to Kashin-Beck disease.[4] The primary symptom of Keshan disease is myocardial necrosis, leading to weakening of the heart. Kashin-Beck disease results in atrophy, degeneration and necrosis of cartilage tissue.[5] Keshan disease also makes the body more susceptible to illness caused by other nutritional, biochemical, or infectious diseases..."
"Signs of zinc deficiency include hair loss, skin lesions, diarrhea, and wasting of body tissues. It is rarely recognised that lack of zinc can contribute to acne. Eyesight, taste,[9][10][11][12][13] smell and memory are also connected with zinc. A deficiency in zinc can cause malfunctions of these organs and functions. Congenital abnormalities causing zinc deficiency may lead to a disease called acrodermatitis enteropathica..."
"The symptoms of chromium deficiency caused by long-term total parenteral nutrition are severely impaired glucose tolerance, a loss of weight, and confusion.[10] Another patient also developed nerve damage (peripheral neuropathy)..."
"Copper deficiency can cause a syndrome of anemia or pancytopenia and a neurodegeneration in humans or other mammals. The neurodegenerative syndrome of copper deficiency has been recognized for some time in ruminant animals, in which it is commonly known as "swayback". Affected animals develop ataxia and spasticity...
Symptoms of magnesium deficiency include: hyperexcitability, muscle weakness and tiredness.[1] Severe magnesium deficiency can cause death from heart failure."

Fortunately, these deficiencies essentially don't occur because these metals are ubiquitously found in a broad spectrum of common foods, making it next to impossible to be deficient in them. They happen to occur in these foods in precisely the right ratios that serve our bodily needs without being so concentrated as to be toxic (and most of these are toxic in high concentrations). It's also worth noting that there is no such thing as Uranium deficiency or Ytterbium deficiency. It is only those metals which are present in the soil in somewhat predictable concentrations, are absorbed by the roots of plants, and thus ended up in the diet of our ancestors.

So the question is: If there never existed any Zinc or Selenium in our diets, would we be as healthy? The answer almost surely is yes. The fact that Zinc is involved in a number of chemical pathways that regulate healthy body tissues was borne of the fact that Zinc molecules were the most convenient and useful molecules for this function and were available in the necessary concentrations to pursue that solution to tissue development. If it had never been available, the body would have adopted a different, but probably nearly as successful solution set. Adaptations, whether biological/evolutionary or those that are part of the lifestyle of living things flow like rivers and electrons, through the path of least resistance. What I'm claiming here is nothing very new or insightful, but a key concept that flows from this understanding, is that once these adaptations are in place, they can become cemented in place, and thus are very hard to change, requiring substantial amounts of time and investment in developing new adaptations.
Think of cell phones. Twenty years ago, cell phones were a very fringe technology. No one but the rich or neuveuax chic businessy types had them. If they completely disappeared, not very much would have been disrupted. But cell phones found an adaptive niche because they allowed people to decouple distance communication with wall-mounted devices. This type of communication could reach places it never reached before, and investment in increasingly outdated methods like land lines dried up, both in physical existence, and in the habits of everyday people and business models of companies. Pay phones have also been disappearing at a rapid rate everywhere from airports to 7-11's. It's not hard to imagine a decade or two down the road, the traditional landline going the way of the telegraph.
To anyone alive today, and observing this shift, it must be obvious that the switch to cell phones engenders more convenience and efficiency in distance communication. It must also be obvious that the change does not occur overnight, but over the course of decades, as peoples' habits had to slowly adapt, and cell phone infrastructure had to be gradually built and refined to enable better service with fewer dropped calls, etc, and for learning curves and economies of scale to develop to such and extent that cell phones were affordable for a critical mass of the population.
What is not often considered in a world that views history through the lens of progress, is that adaptation in the reverse direction takes nearly as much time and investment. If Selenium mysteriously disappeared from our diets overnight, the change would cause a brutal shock to human populations, and it would take many many generations for a suitable replacement series of chemical pathways to be erected within our systems. Likewise, if cell phone towers suddenly stopped working tomorrow, communication and commerce would suffer a substantial blow, and economic systems that once never gave a thought to cell phones would find themselves crippled.
There are countless examples of this kind of situation in modern societies. Technologies that are vastly complex and require large investments in educational training, energy, and supply chain inputs from around the world are increasingly cemented into our functionality as a society.
While it is certainly hyberbole to suggest that these technologies might disappear tomorrow, one can certainly envision a host of scenarios where some of these technologies might be rapidly disrupted on a large scale - perhaps through targeted warfare, natural disasters, or economic depression. The extent to which this becomes a crippling problem for society depends largely on the pace of the change - whether it outpaces our abilities to adapt or not.
This is also the central problem underlying human-induced climate change. It is not that it's never been warmer than it is today or will be in 50 years. Indeed, it's been much warmer in millenia past. It's that the pace of predicted change in many places will likely exceed many species' (and by extension many ecosystems') ability to adapt. Periods of such rapid climate change are rare in the past, but are usually asscociated with mass extinction, or large die-offs in population of certain species.

Back to the topic of technology - there are preemptive strategies for weathering possible shocks to our intensive technology systems. These involve finding ways to reduce dependence in one's own life on high technology - either by choosing not to adopt exceedingly intensive devices in one's lifestyle, or by building in redundancies - low tech means of doing the same thing that can be kept on hand and deployed easily if necessary. This might include having a bike (and investing in keeping your body in shape) or living close to public transportation in the event that a serious oil shock makes car transportation unavailbale for a time. Holding on to traditional ways of doing things as redundancies in our lives can often be very rewarding for their own sake. Whether or not I ever have to rely on my own backyard garden for sustenance, I can say emphatically that riding my bike out to our community garden plot and strolling trough our little rows of sprouting plants, as sparrows flit about, rabbits bound around, and white clouds drift overhead brings a renewed sense of connectedness and happiness to my life.