Author: Jeremy Taylor
Every chapter of this book is filled with nuggets of wisdom. Taylor looks for an evolutionary angle to enlighten us on the causes of some of the most critical ailments that plague the human body. He starts with the well known fact that humans are comprised of 90% microbes and only 10% cells. Nevertheless the history of medicine has focused mainly on understanding the functioning (and dysfunction) of our organs. In the first chapter Taylor highlights the role of the intestinal bacteria and helminths (parasitic worms) in regulating our internal equilibrium. The depletion of some of these “old friends” can result in many allergic and auto-immune conditions.
The next stop on the Evolution Theory Tour is an explanation of human fertility or more accurately “infertility”. To start with Taylor points out that during a pregnancy the genetic interests of the mother, father and the baby are engaged in a tug of war. It is fascinating to read how their tug of war is at all levels and first takes place between the father and mother. First the chemicals in the semen are evaluated for their fit. Then, the paternal and maternal copies of the genes duke it out in a literal tug of war. Taylor describes an experiment where a copy of the same gene on the chromosome from the mother/father is manipulated. If either one of them was silenced it result in the fetus being significantly above/blow the baseline for a normal offspring. Ergo, we really need both copies of the gene to find the right balance.
The mother rejects poor quality embryos so she can preserve her scarce opportunities to propagate her genes and maximize the potential for raising a healthy offspring. Miscarriages are very common and most of them are not even registered as they happen even before a pregnancy is detected. In the author’s words “the embryo and fetus are in a constant state of probation until birth."
In the next chapter, Taylor discusses the vexing back pains that 80% of adults suffer from at some point or the other in their lives. Contrary to common belief, the author states that the cause is solely because we stand upright. In fact, changing from a horizontal to vertical posture doesn’t change the compressive pressure on the vertebrae in any significant way. It is the leveraged activities like heavy lifting or gardening that put an order of magnitude more pressure on the vertebral muscles that can result in injury. In case you are wondering what the evolutionary advantage of standing upright is, Taylor’s view is that it enabled us to decouple our stride from our respiration, thereby allowing us to run continuously for long periods of time. In contrast, quadrupeds can’t pant and gallop at the same time so that even the fastest animals can a sustain burst of speed for only a few minutes at a time.
The next stop on the evolutionary tour is the form and function of the human eye. While it is one of our more impressive organs, it is not a marvel of Engineering genius. The photosensitive cells are facing the outside of an inverted cup retina and a jumble of nerves on the inside carry the signal out through the optic nerve, resulting in a blind spot at the center of the retina. While at first glance this seems like a bad design, Taylor puts forth some theories on who and why this could have evolved in humans. He goes on to explain how there have been many independent evolutions of eyes on this planet, estimating anywhere from 40 to 65 independent outcomes.
No book on medicine would be complete without a discussion on cancer and Taylor does not disappoint. He points out that there are many different types of cancer and even a single tumor can have multiple groups of cells with different mutations with varied genetic makeup. Thus it is very unlikely that we will discover a singular cure for all types of cancer.
Finally Taylor closes out the book with an in-depth look at the cause and effect of Alzheimers. For me, this chapter had a very special significance as the cloud of Alzheimers hung over the last few years of my father’s life. For a long time, conventional wisdom maintained that Alzheimers was caused by beta amyloid plaque deposits on the neurons in the cortical region of the brain. Taylor argues quite convincingly the the plaque, while clearly present in Alzheimers patients, may be a symptom and not really the cause of the disease. He points to recent studies that show that in an overwhelming majority of cases, Alzheimers patients have inflammation of brain tissue and may be the result of an underlying infection that has leaked into the brain. The amyloid plaque might just be an immune response to try and contain the spread of infection.
In summary, this book makes a strong case of taking an evolutionary view to the treatment of the complex diseases that currently afflict the human race. While it is quite readable, it veers into textbook territory with a multitude of technical jargon and acronyms. Nevertheless it is a must-read for anyone who is curious about what the future medical treatment has in store for us.
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