Disorders may come from evolution experimenting on us
By: Tim Andersen
Tags: Intelligent Design, Human Body, Darwinism, Evolution

Photo by Johannes Plenio on Unsplash

That evolution occurs is a fact. We can see it in the fossil record. We can observe it in the study of finches in the Galapagos islands. We can infer it in species like koalas that adapted to eat only one kind of food.

That human beings are also a product of evolution is clear. We are related to a number of species both by morphology (shape and function) and by DNA. Although in many areas we are outliers (certainly in intelligence) there is nothing that suggests we are not products of an evolutionary chain stretching back millions of years, culminating in a set of adaptations that resulted in our present subspecies of Homo Sapiens Sapiens about 200,000 years ago.

Evolution occurs when a change in a gene creates some change in the body that results in either better survival or better chance of reproducing. There are two ways this can happen: through random events or through sexual reproduction.

Evolution by random changes is very slow, requiring many, many generations to introduce any advantage. It is the main way that microbes evolve which is why, even with extremely short generations, they take a while to evolve new abilities. About 1/2 billion years ago, life had been evolving extremely slowly when sexual reproduction evolved. At that point, life exploded into a huge variety of forms during the Cambrian explosion. Why?

It is because sexual reproduction allows for beneficial traits from different members of the same species to be combined. While random changes can at most introduce one beneficial trait in a line, sexual reproduction can spread those traits to the entire species. This means that beneficial traits can occur in any member of the species and eventually you will find all those traits in all members after a few generations. When there are changes in the environment that make certain traits more valuable, like changes in climate for example requiring thicker or thinner fur, existing members of the species with those traits will gain preference, produce more young, and eventually replace members that lack that trait. Sexual reproduction is, by far, the main way that evolution makes progress.

Because of the shifting way that evolution proceeds, combining traits from one environment, adapting them to new environments, and making progress through reproduction and survival, species can develop traits that may not be the best possible adaptation. After all, adaptations occur piecemeal, building on existing morphology. There is no rule that says that evolution has to provide the best possible design. It only seeks survival for its own sake.

A number of arguments have appeared in recent years suggesting that the human body is an example of a bad or at least suboptimal design. While the argument has been cast as one between those who support atheistic evolution and those who support intelligent design (with perhaps evolution being the mechanism the creator uses but gently guiding it to a desired form), whatever you believe about how evolution works, the basic premise that the human body is suboptimal is questionable.

Firstly, let’s discuss the main “problems” with the human body (sometimes extended to other land animals). These are things like the eye, knee, back, and feet.

The problem of the eye was brought up on Cosmos with Neil deGrasse Tyson, some years ago, probably because the complexity of the eye has been suggested as an argument against evolution. There are certainly better eyes in the animal kingdom, but the human eye evolved for a specific purpose and doesn’t appear to be seriously flawed. Tyson also mentioned the proximity of the genitals to the anus and urethra as a design issue. That quip doesn’t really point out a specific design flaw. My faucet is close to my drain and my fridge to my trash can all for good reason.

My argument here isn’t about what a creator would or would not create (do I think a creator would create a flawed being? yes. The story of Adam and Eve suggests He may have and some theologians make this assertion), but rather whether the human body is genuinely flawed from a design perspective. If it is flawed, one would expect to see other species to have evolved far superior versions.

My main argument here is that human beings are actually very well adapted and a good design for the environment in which we generally evolved, on the savannas of West Africa, as hunter gatherers, and that the primary reason why we see our bodies as flawed is largely for two reasons: (1) agriculture and civilization or (2) because there isn’t just one evolved design of the human body and evolution requires introducing design flaws in order to find design successes.

The feet are a good example of #1. For most of our evolution and indeed still in some parts of the world, people went barefoot most of the time or wore light sandals. The development of closed toed shoes in their many varieties that we have now and the further development of mass produced, generically sized shoes are generally the reason for modern foot problems. Indeed, foot problems are rare in places where shoes are rare.

The same goes for teeth. In modern nations regular dental care, brushing, and flossing are required to keep your teeth your entire life. Before such things (even 100 years ago) it was common for people to lose all their teeth by middle age. There is a flawed argument that this is because people in ancient times didn’t live past middle age (or didn’t need to) and so didn’t need teeth beyond that point. We know for a fact that people regularly lived to old age in ancient times.

Archaeological studies have pointed to a better explanation: hunter gatherers tend to keep all their teeth while farmers don’t. (Indeed, they were better than ours.) The reason is the high starch content in the farmer’s diet (from corn, potatoes, wheat, or rice). While farming can feed a great many more people than hunting and gathering, it has been, until the last 200 years or so, pretty hard on the human body not only in terms of the work required but in the lack of nutrition. Indeed, it was found that hunter gatherers were not only healthier and more toothful than their farming contemporaries but also taller.

These days paleo diets are all the rage for this reason, although it is questionable if these diets are truly what our ancestors ate. Certainly eating mainly fibrous sources of protein and carbohydrates, no sugar, refined flour, or white potatoes, as well as lean meats (and organ meats) will help your teeth.

The knee is another body part that gets a lot of blame. This argument is confusing because the knee evolved shortly after legs and has stayed very similar to its current design in most animal species. It is at least 360 million years old. The knee is an amazing piece of engineering, in fact, for it is designed not only to provide sufficient torque on the lower leg to move quickly, jump, and sit and stand, but also to provide the body with stability. The kneecap and a set of ligaments and tendons in the knee play a role in this. Indeed, the kneecap acts as a sort of fulcrum or pulley for the quadricep to pull the lower leg, increasing the force versus if it weren’t there. Therefore, I won’t even address objections to the general design. It is clearly successful. Rather, I focus on the human variation.

The human knee enlarged and became more strictly controlled to support bipedal motion and standing upright. It has a special locking mechanism that enables us to stand upright for long periods of time without our legs getting tired that apes lack. (An ape standing “upright” would tire extremely quickly as you would if you stood with your knees bent instead of upright.) Once the human knee evolved, it must have spread very quickly to give our ancient ancestor species upright locomotion. Unfortunately, it is a very specialized design.

Studies of knee osteoarthritis have shown that many of the problems with knees arise because of genetic variations from the original knee design. That is, the knee evolved with a very tightly constrained design and over time flaws have crept in such that the elderly with those genetic drifts now suffer from degradation and pain. This may be true of other joints as well, suggesting that the price we pay to evolve, genetic variation, is the culprit.

The human spine suffers from a similar problem of evolutionary drift. Studies have shown that humans who suffer from a spinal disorder spondylolysis have spines that are morphologically more different from our great ape cousins (who do not experience this disorder) than healthy spines. The implication here is that evolution found an ideal spine but again genetic drift and variation has resulted in suboptimal versions. The spine in some people “overshot” the optimal shape.

You can apply this reasoning to other areas like the width of women’s hips versus the size of a baby’s skull. There are tradeoffs in the design and some lose and some win.

Indeed, the whole downside of evolution is that it requires variation in order to make progress and that means that there are winners and losers in the evolutionary game. If you have a disorder that arises from some genetic variation, you are a loser (at least at that part of the game). But if you have some variation that makes you free of a disorder, then you are a winner.

The result is that if winners at some evolutionary adaptations but losers at others reproduce with those with complementary flaws and successes, then their children may be more likely to inherit an optimal design. Of course, they are just as likely to inherit a more flawed design. Evolution is merciless in that way. The children who are “winners” will go on to live longer and pass on their winning traits while the losers are lost in the dust of history. You are only here because you descend from an unbroken line of these winners.

With advances in medical science, of course, many of the debilitating flaws that evolution (and modern society) have introduced in us can be mitigated or eliminated. What does this mean for natural selection? The likely result is that flaws that can and are addressed medically in the vast majority of the population (certainly not the case now with much of the world still living with minimal access to healthcare) will remain in the gene pool while those that can’t or aren’t will be weeded out. Behavioral instincts like willingness to reproduce may be a bigger factor than a strong back in the future. As far as we know natural selection is blind (there is no evidence it is being guided in any way); thus, it is up to us to learn how to deal with the curve balls it throws at us.