The human body has changed over the past few thousand years to handle the environmental shifts that occur. From generation to generation, Darwin believed that natural selection has weeded out the weaker in favor of the stronger. Lamarck believed that changes occurred during the lifetime. Modern science is showing us that our genome is read in differing ways to make these intra lifetime adjustments.
In Daniel Lieberman's book, The Story of the Human Body, we see an anthropologic understanding of why these shifts occurred and how we can learn from them for the future.
Many years ago, death rates were high in the first five years of life owing to infectious diseases. Now we are living longer because of the advent of sanitation, antibiotics, nutrition and vaccines.
Unfortunately, we are now slated to live longer but many will die slowly with chronic disease. Where did it go wrong?
Human adaptations have taken place for the sole purpose of fostering future offspring in order to keep the species alive. For example, the adaptation to turn sugar preferentially into fat would have benefited humans in times of feast and famine. The fat storage would allow a population with this genotype to have a competitive advantage akin to a giraffe in an area with tall trees and no shrubbery. Surviving the cold winter allows the species to propagate.
"Your bodies various adaptations were selected to help your ancestors survive and reproduce in an untold number of distant incarnations, not just as hunter gatherers, but also more recently as farmers."
"These adaptations explain and constrain how your body functions in terms of how you digest, think, reproduce, sleep, walk, run, and more. It follows that considering the bodies long evolutionary history helps explain why you and others get sick or injured when you behave in ways for which you are poorly or insufficiently adapted."
Why is this such a big deal now?
The last 100 years have been an unprecedented era of rapid change and our bodies have not evolved fast enough to mitigate the negative effects of change. Take the previous example of the sugar to fat genotype. Now we have an overabundance of sugar and no starvation cycles. Mismatch = disease.
We evolved as running and hard working humans ill adapted to sit at a desk and work 8 hours on a computer. Consequences: Increased back pain, flat feet, weak muscles, etc..
Over time, it is likely that we will select out genes that are suited to this new lifestyle. However, until this occurs the price of this is turning out to be economically and pathologically devastating.
Take Home Point:
Think of your ancestors and the lifestyle that they led as a guide to your future health. Make decisions based on the principles of natural intent and your recent evolution. Your health depends on the decisions that you make for yourself and your children.
To be continued.....
