Why is obesity a problem today? Why does high blood pressure and diabetes continue to rise, while cardiovascular disease remains the number one killer across the globe?
One theory is called the evolutionary mismatch theory. In a nutshell, it is about the mismatch between how our DNA has evolved over millions of years and the ways in which we live in modern society.
One of the difficult parts of grasping this theory, is trying to get a sense of just how long it takes for evolution to shift genetics. It is also difficult to simply grasp the timeline of human civilization, especially as it relates to our evolution as a species.
Carl Sagan once presented a similar timeline for understanding the development of the universe - another scale that is impossible to truly grasp. By putting the start of the universe - the big bang - on January 1st at 12:00 AM in the morning, a year-long calendar was scaled to make midnight on December 31st today.
In the same light, here is a calendar showing how diet and evolution relate on a timeline. Our hominin ancestors developed on January 1st at 12:00 AM. We were moving out the trees and onto the grasslands. Our diets started shifting as we began to forage and hunt.
It wasn’t until the end of August that the genus homo began to appear. Different species of the genus homo populated the Earth, but it wasn’t until December 23rd that homo sapiens (i.e. modern humans) appear.
In fact, it isn’t until December 30th, the second to last day of the year, that Neanderthals finally became extinct.
All of this time, we have still been hunters and gatherers. Diet and evolution have been progressing together, for millions of years.
Then, a shift happens in the afternoon of New Year’s Eve at around 1:03 PM.
Agriculture is born.
It isn’t until this very recent invention that our modern species began to systematically cultivate croplands. But still, much was needed to be learned over the ensuing thousands of years for agriculture to reach what it is today.
At around 11:53 PM on December 31st, caloric abundance occurs. At nearly the present moment on an evolutionary timeline, we have (in the developed world) removed the scarcity once associated with obtaining calories.
It is no longer difficult for most people to meet their caloric needs. Calories are abundant and cheap. And thus, extra calories are no longer a chore to obtain.
The chore is now to abstain from excess.
Thus, the explosion in modern-day overconsumption has emerged.
Diet and evolution move together, but genetics does not shift as fast as our technology and our culture. Thousands of years of agriculture may seem like a long time. And indeed, some genetic shifts due to agriculture have happened in humans over this timeline.
For example, the ability to digest lactose (in some of the population) has evolved since the development of dairy agriculture.
But our basic metabolism is well established and well conserved across many species. And therefore, our ability to retain and store calories and fat has planted itself firmly into our biochemical processes for life.
These processes have kept our species alive for millions of years - without abrupt changes through 364 and ½ days of the year. But our DNA won’t shift quickly in those final minutes of the year - nor arguably at all if it does not affect reproductive success.
In addition to our ability to efficiently store calories, diet and evolution progressed in parallel alongside a varied diet.
Studies of past hunter gatherer societies, as well as modern day tribes in Africa, South America, and Australia, demonstrate a varied diet that changes by location and season. And along with a varied diet is a diverse gut microbiome and greatly reduced numbers of chronic diseases that afflict the modern world. This dietary diversity is in stark contrast to our diets following the birth of agriculture.
It’s easy to assume that human progress always improves along an ever-increasing, linear path. Why would society adopt new cultural practices or technological innovations if they make us worse off?
Sometimes, hindsight is twenty-twenty. Archaeologists over the last few decades have been finding more evidence that agriculture’s effect on diet was, before the last 75 years or so in developed nations, a step in the wrong direction with respect to nutritional health.
Along with a positive increase in access to calories, nutritional deficiencies increased too.
The neolithic revolution (agricultural revolution) appears to have increased the extent of nutritional deficiencies and decreased nutritional health. Cases of iron deficiency were often more prevalent and episodes of malnutrition became more severe. These are evidenced in the skeletal remains early societies. Defects in bone and teeth structures can reflect episodes of malnutrition, and an increase in severity occurred after the switch to farming. Why?
Diets, focused on grain staples, became less varied.
The diets of hunter gatherers were more varied compared to their agricultural descendents. Once farmers began consistently growing staples like corn, wheat, and rice, nutrient variety and quality decreased despite the increase in caloric intake. Agriculture could produce more food and support greater populations, but they did so at the cost of fewer nutrients and nutritional health. The results?
Poorer health outcomes afflicted agriculturists.
The neolithic revolution immediately brought higher child mortality rates, a reduction in height, shorter life expectancy, and higher tooth decay all presumably due in part to dietary changes. Add to these perils an increase in infectious diseases due to immobile communities living in close quarters with farm animals and poor sanitary conditions, and some have called the advent of agriculture The Worst Mistake in the History of the Human Race.
Nutrition, in the developed world, has regained much of what it lost.
Developed nations have been gradually paying more attention to proper nutrition. Despite an arguably less varied diet than our ancient, nomadic brethren, we have been supplementing staples with nutrients that have improved health outcomes.
But the developing world still struggles, and even the developed world is far from optimal. Evolution has optimized our diets to fit hunter gatherers’ lifestyles for millions of years before the advent of agriculture drastically altered our pattern of nutrient consumption.
And some of the Blue Zones today show us that a more traditional diet, varied and moderate in caloric intake, produces superior health and longevity.
The stories of diet and evolution are intertwined. So let the past remind us of the value in a varied diet. Eat nutritious foods, and do so for life. Our genes, and our health, would prefer it.
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