Stone Age Genes in the Modern World

evolution-human-waistline

Evolution of the human waistline. Ancient genes and modern environments don’t mix well.

With the exception of those who cling to creationism as the explanation for human existence on earth, most people accept that the emergence of our species, Homo sapiens sapiens, came as a result of eons of evolution – and they acknowledge that we’re just another one of the many animal species found on the tree of life. Regardless, as humans, we tend to look at ourselves as separated from the rest of the lifeforms on our planet. After all, we’re so different in so many respects; we live in large cities, drive cars, make music and art, and connect with each other through online platforms and phones. Some would even say that we tower over the rest of life on earth, as we lock other animals up in zoos, tear natural habitats down to create new apartment complexes, and have developed means of controlling and combatting pathogenic microorganisms. For a suit-wearing and coffee-drinking office worker on the 10th floor of a large commercial building it’s easy to feel shut off from nature, and the fact that we share most of our DNA with chimpanzees might seem more like a fun fact than a reminder that we are very much a part of the rest of the animal kingdom on earth.

When the human and chimpanzee lineages diverged about 5 to 7 million years ago, hominins split off into a very different evolutionary path. Perhaps the most important initial adaptation was our ability to walk on two legs, which was advantageous for a number of reasons, one of which being that it made us better able to walk long distances in the search for food. This ability to walk on two legs – bipedalism – was a crucial adaptation that set the stage for other major evolutionary events that made us who we are today. Most important in the context of this post is our massive and complex brains, which have been the engines fueling our rapid cultural evolution. Because that’s really the one fundamental thing that makes us an unusual species and separates us from the apes: our ability to express ourselves through culture. We’re driven towards innovation – and we pass on behavior patterns, arts, beliefs, institutions, and all other products of human work and thought to new generations.

Evolutionary mismatches

Darwinian evolution is a slow and tedious process where natural selection acts to either increase or decrease the frequency of heritable biological traits in a population over time. Cultural evolution on the other hand can be rapid – and it is today by far the most potent form of evolution. Our ability to innovate ourselves through culture has been a marked characteristic of our genus ever since the emergence about 2.3-2.4 million years ago, but it wasn’t until the agricultural revolution – and perhaps even more so the industrial revolution – that it really took off. Perhaps most importantly to this blog, we have developed new means of producing, handling, and processing food, we have created transportation devices that ameliorate our need to move our bodies, we have designed new drugs, foods, and cosmetic products that alter the microbial communities living in and on us, and we have invented artificial lighting that allow us to stay up long after dark.

Many of the technological-, economic- and medical-“advancements” have clearly made life easier for us, and I think few people would say that they’d like to leave the convenience and comfort of modern living and adopt a hunter-gatherer lifestyle alongside the Bushmen in Africa. However, there’s no doubt that the varying speeds of cultural and biological evolution have a profound impact on human health and well-being.

The biological adaptations that have occurred since the agricultural revolution are just a drop in the pond compared to the profound changes to our living conditions during this time, and as a result we’re now experiencing a gene-environment mismatch (1, 2, 3). Suddenly, ancient genes that were adaptive in the past are setting us up for disease in the present by driving us to eat fast food and live a sedentary life.

Suddenly – in the blink of an eye from an evolutionary perspective – we’ve moved from a savanna in Africa teeming with wildlife to concrete pavements in the middle of large cities filled with convenience stores, apartment complexes, and office buildings.

If we were smart enough to expand our scope and look at our species from the perspective of an outsider, we would see that we’re in a situation very similar to that of domesticated animals trapped in unnatural living conditions. With the obvious difference being that we’re free to move about the world, the similarities between sick livestock and ourselves are many. We eat foods we’re not well adapted to eat, we’re chronically stressed, we don’t move our bodies as much as we should, etc. Essentially, it all boils down to putting an organism into novel conditions it is not adapted for.

The evolutionary road of our species is extremely important to have in the back of our heads when discussing health & disease, as “physical activity, sleep, sun exposure and dietary needs of every living organism (including humans) are genetically determined” (4). In other words, the solution – as always – is to take charge of our own health and adopt a lifestyle that is more in line with our evolutionary heritage.

Comments

  1. Very insightful. Thanks!

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