The Story of the Human Body: Evolution, Health, and Disease

The human body has evolved in a different environment than it exists in today. We have many innovations that make our life "easier" today. However, these same innovations also take away some of the needed stresses that help our body body to properly develop and fight of ailments. 

The book starts with the origins of humans. Early hominids started to walk upright millions of years ago. This created many challenges, but also gave some advantages. (After all, they did not become extinct.) Brain size also increase. (There is still debate as to what caused what.) Eventually, homo sapien spread across the world, primarily as a hunter-gatherer society.

The human body is fairly well optimized for hunting and gathering life. This type of life required a great deal of physical exercise. It also required a lot of chewing (Which helped lead to good dental appearance.) Sweet food was prized and stored up. Humans store more fat than many other animals, giving advantages in survival. People have infrequent births, but a higher likelihood of a child living longer. Birthing is not easy. However, the wider hips allow for larger babies to be born, though they still need more attention after birth.

Our ailments today often come from "too much" or "too little". We have processed food to give us the primary energy that we crave. Our genes encourage us to stock up on this food and store it away. Alas, this lead to obesity and a number of other ailments. On the too little side, we don't move enough. Our bones and muscles are strengthened by stresses. 

Our medical system focuses on treating symptoms rather than making lifestyle changes to reduce causes. This has inadvertently resulted in some negative evolution of disease. Social evolution has a curious interaction with different conditions. (Is near-sightedness more common because of related benefits? Or is it because it has little harm and is easily fixed?) Many diseases today also appear later in life, causing little negative pressure on reproduction.  

Looking at the "long" picture provides an interesting insight into the human condition as well as some concerns about the way we are practicing medicine today.

Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

Humans were never meant to exercise. They do, however, get great benefit from physical activity. This conundrum is explained by the advances in human society. Hunter gatherers require a large amount of energy to obtain their food. (Sometimes, a hunter might run dozens of miles to chase prey.) It is beneficial to minimize this expenditure whenever possible. Yet because the expenditures are so great, the body has used this forms of physical activity to help optimize provide benefits systems. Today, we have managed to eliminate almost all need for physical activity. However, are bodies are still configured to require this physical activity to carry out some of its "repair" mechanisms. Thus, the need for voluntary exercise has been born.

What does exercise help? The general answer is "a lot". There have been numerous scientific studies performed. Moderate levels of exercise seem to be beneficial in preventing various diseases and increasing overall health. More exercise seems to add even more benefits. Extreme levels of exercise (like ultra-marathons) may show some decrease in immune response. Aerobic exercise and strength training both seem to be beneficial, though for different things. A mixture of both is optimal, though if just doing one, aerobic exercise seems to get a greater bang for the buck.

One challenge with exercise studies in general is that they don't easily fit in the paradigm of scientific studies. The short term studies may rely on people reporting activity or are narrowly focused on a single outcome for a level of physical activity. Long term studies can be useful, but also require a lot of self reporting to be done. It is also important to look at the numbers behind studies (as there may be groups with very small sample sizes.) There are some interesting studies out there, including one that shows taking antioxidants may reduce the positive antioxidant impacts of exercise. Our bodies can do interesting things.

Exercise can be helpful in weight loss as long as increased calories are not consumed to compensate. One of the challenges is the body itself. It responds to needs by managing the number of calories that are burned. Thus, diet is often more beneficial for losing weight and keeping it off. 

Prescribing a healthy diet, enough sleep and regular exercise would probably do more to improve human health than any medication that could be prescribed. Alas, getting people to exercise can be a challenge. We often mandate physical activity for young children, but feel we can't do it for adults. Some people enjoy individual activity, while many others thrive on the comradery of group fitness. Fat-shaming is seen as something bad. There are many data points that are parroted out there that don't necessarily have scientific validation. (10,000 steps a day was a standard set by a pedometer maker.) Different people respond better to different physical activities. How do we help people to improve their health?